Introduction

Purpose

This report provides an overview of U.S. overseas military bases, as well as information concerning their functions, management, resourcing, and related issues for congressional consideration. Its contents are unclassified, and the terms and methods used herein may differ from those used by the Department of Defense (DOD) or other executive branch organizations.¹ Additionally, because of the unclassified nature of this report, classified materials—for example, DOD's Enduring Location Master List (ELML)—were not used in its preparation.²

Methodology

To identify active U.S. overseas bases, CRS used a number of unclassified sources, the most foundational of which were DOD's annual Base Structure Reports (BSRs).³ Other U.S. government sources used in its preparation included budget justification documents for military construction (MILCON) at overseas locations; DOD press releases and public statements (including individual unit and installation websites); executive reporting pursuant to the War Powers Resolution; Department of State press releases, Integrated Country Strategies, and related documentation; congressional testimony, reports, and related documentation; and information provided by executive branch officials and organizations. In addition, media reports were used to supplement government-provided information as necessary.

To characterize active U.S. overseas bases, this report sorts locations identified from the above sources into one of two categories. The first, persistent bases, includes overseas sites that have been continuously used by DOD for at least 15 years and at which the U.S. military exercises some degree of operational control (this category tends to include DOD's largest and most well-known bases).⁴ The second, selected other U.S. military sites, includes overseas sites that do not meet one or both of the criteria for persistent bases, but at which DOD maintains some sort of territorially linked presence or access.⁵ This report does not include locations that DOD may use on a temporary basis for military exercises or contingency operations without intending to make persistent sites of U.S. military activity.⁶

Applying the criteria developed above, this report identifies 68 persistent bases and 60 other U.S. military sites across the Indo-Pacific, Europe, the Middle East, Africa, and Central/South America and the Caribbean.

Background

Defining Overseas Bases

The U.S. Department of Defense maintains a network of thousands of buildings, fixed structures, real property, and other defense infrastructure to carry out its mission to provide the nation with military forces to deter aggression and prevail in conflict.⁷ The basic administrative unit into which DOD groups its infrastructure is the installation, which is statutorily defined as any "base, camp, post, station, yard, center, or other activity under the jurisdiction … [or] operational control of the Secretary of a military department or the Secretary of Defense."⁸ An installation or group of installations may, in turn, serve as a base, which DOD defines as "a locality from which operations are projected or supported."⁹ Bases located outside the United States and its territories are commonly referred to as overseas bases.¹⁰

Overseas bases perform or support a variety of military functions, including

• Basing of personnel and equipment. The most elementary function of overseas bases is to provide secure spaces for U.S. servicemembers, weapons systems, munitions, and supplies, thus enabling the United States to maintain and employ military capabilities in regions outside its territory. Bases serve as work sites during both peacetime and wartime, supporting activities ranging from routine office work to the launching of combat aircraft; larger installations may also include housing for DOD personnel and their dependents, as well as morale, welfare and recreation facilities.
• Domain awareness and area defense. Overseas bases may play an active role in detecting, defending against, and otherwise countering adversary threats to U.S. and allied/partner forces, facilities, and territory (by hosting, for example, radar facilities or ground-based missile interceptor sites).
• Maintenance and repair. Overseas bases may host specialized facilities, equipment, and personnel to maintain, repair, and overhaul weapons systems and other defense equipment outside of U.S. territory. Examples of such facilities may include vehicle maintenance facilities, aircraft maintenance hangars, and naval drydocks.
• Training and exercises. Overseas bases may contain training and exercise areas intended to maintain and enhance U.S. and allied/partner readiness, test plans and concepts, and demonstrate and improve interoperability.

Why Does the United States Maintain Overseas Bases?

DOD considers the placement and organization of overseas bases—together with the positioning of forces and the structuring of international security agreements—to constitute its global defense posture.¹¹ According to DOD Instruction 3000.12, DOD's global defense posture "is the fundamental enabler of U.S. defense activities and military operations overseas and is also central to defining and communicating U.S. strategic interests to allies, partners, and adversaries."¹²

Considered broadly, overseas bases support the ability of the United States to project and sustain military power beyond its territorial bounds. They enable DOD to maintain a persistent presence in areas that the U.S. government determines are important to the national interest, and can facilitate rapid responses to sudden crises or emergencies. They also signal U.S. intentions to other international actors, which may support a variety of strategic aims.¹³ For instance, the presence of overseas bases in a region outside U.S. territory may communicate to allies and adversaries alike that the United States views geostrategic developments there as directly relevant to its national security. The presence of overseas bases may also contribute to the defensibility of ally/partner territory, and deny U.S. rivals or adversaries access to strategically significant locations.¹⁴

For a more detailed consideration of the potential advantages and drawbacks of overseas basing, refer to the "Overseas Basing and National Strategy" subsection of this report's "Issues for Congress" section.

Historical Development

Overseas basing has played a significant role in recent U.S. military history, and much of DOD's current footprint abroad continues to reflect decisions made in the last century (of the 68 persistent military bases identified in this report, for example, 56 were established during the Cold War).

Although the first permanent military facilities abroad date to the late 19^th century, overseas basing did not play a major role in U.S. strategy until World War II.¹⁵ Following America's entry into that conflict, the U.S. military established and used hundreds of overseas bases to support its combat operations. These overseas bases included locations in Europe and the Pacific (the U.S. Army Air Forces used over 200 airfields in the United Kingdom alone, for example), as well as sites outside the war's main theaters (e.g., Natal-Fortaleza in Brazil, Camp Amirabad in Iran).¹⁶ After 1945, the United States continued to use certain of these locations, along with newly established bases in the territories of defeated Axis powers, to support occupation and reconstruction activities.¹⁷ Although some policymakers did not expect this global presence to last longer than a few years, the onset of the Cold War in the late 1940s led the United States to maintain and expand its network of overseas bases, particularly in Western Europe and East Asia.¹⁸ This footprint quickly became a major factor in U.S. and allied strategic planning, enabling the projection of military power into distant, geopolitically contested regions.¹⁹

Although certain core aims of U.S. strategy during the Cold War remained consistent (e.g., to deter—and failing that, prevail in—conflict with the Soviet Union), DOD's overseas basing posture during this period was not static. In some cases, unforeseen political developments, such as the French government's 1966 decision to expel from its territory all military forces under foreign command, could result in base closures.²⁰ In other cases, changing military requirements, such as those stemming from U.S. involvement in the Vietnam War, could lead to the rapid expansion of basing in a particular region.²¹ In 1991—the last year of the Cold War—DOD reported maintaining 134 bases in 18 different countries, with locations in Germany, the United Kingdom, Japan, South Korea, and the Philippines accounting for the majority of listed bases.²²

The fall of the Soviet Union led to significant changes in America's overseas basing posture. Without a superpower rival, U.S. policymakers assessed that a smaller military presence abroad would suffice to provide for the nation's security, and closed dozens of bases from the North Atlantic to Southeast Asia.²³ In addition, the relative importance of the Middle East to DOD's global posture increased—particularly during the First Gulf War and again following the terror attacks of September 11, 2001—and the United States established new bases in the region.

Although DOD's footprint in Europe and the Indo-Pacific shrank during the 1990s and early 2000s, the reorientation of U.S. strategy around great power competition led to a reversal of this trend by the mid-2010s.²⁴ In Europe, the perceived resurgence of Russia as a geopolitical threat—particularly after the 2014 and 2022 invasions of Ukraine—informed decisions to base U.S. forces in new locations (e.g., Poland) and reactivate U.S. bases in former locations (e.g., Iceland).²⁵ In the Indo-Pacific, strategic competition with the People's Republic of China—the U.S. military's "pacing threat"—motivated DOD to deploy more forces to the region, expand existing infrastructure, and obtain access to new sites in Australia, the Philippines, Papua New Guinea, and elsewhere.²⁶

Compared to its posture during the Cold War, DOD's current overseas basing posture—particularly since 2010—relies less on large, U.S.-operated installations and more on the rotational use of ally/partner-operated sites (an approach sometimes referred to as "places, not bases").²⁷ As Congress and DOD look to the future, the need potentially to support more diversified and distributed operational concepts—for example, the Air Force's Agile Combat Employment (ACE)—may prompt further changes to DOD's overseas basing posture.²⁸

Current Overseas Military Bases

Overview

From a regional and joint perspective, the six geographically organized combatant commands (COCOMs) provide oversight and theater-level direction of the strategic and operational dimensions of DOD's overseas basing posture (see Figure 1).

Figure 1. Geographic COCOMs

Source: FY2023 Agency Financial Report, DOD, November 2023, p. 17. Available at https://comptroller.defense.gov/Portals/45/Documents/afr/fy2023/DoD_FY23_Agency_Financial_Report.pdf.

The following sections provide broad overviews of U.S. basing, regionally organized by COCOM areas of responsibility (AOR).²⁹ More detailed, country-level information on current overseas bases is provided in the Appendix A.

Indo-Pacific

For the purposes of this report, the Indo-Pacific region corresponds to the AOR of the U.S. Indo-Pacific Command (INDOPACOM).³⁰ CRS identified 24 persistent bases and 20 other military sites to which DOD has access within the region.³¹ As of March 2024, approximately 81,000 active-duty servicemembers were permanently assigned to overseas bases in the Indo-Pacific, with the largest number assigned to locations in Japan (54,774) and South Korea (24,234).³²

U.S. forces assigned to overseas bases in the Indo-Pacific include Army and Marine Corps ground units (including the Army's 2^nd Infantry Division, based in South Korea, and the Marine Corps' III Marine Expeditionary Force, based in Okinawa); Navy warships (including an aircraft carrier, destroyers, cruisers, and amphibious assault ships, all based in Japan); and Army, Navy, Marine Corps, and Air Force aircraft (including rotary-wing, fighter, electronic attack, bomber, airlift, tanker, and other aircraft, primarily based in mainland Japan, Okinawa, and South Korea).³³ The U.S. military presence in Japan is overseen by U.S. Forces Japan, and the U.S. military presence in South Korea is overseen by U.S. Forces Korea.³⁴ The headquarters of INDOPACOM is located outside Honolulu, Hawaii.³⁵

The Indo-Pacific is routinely described by DOD officials as the "priority theater."³⁶ The 2022 National Security Strategy characterizes the Indo-Pacific as the "epicenter of 21^st century geopolitics," and the 2022 National Defense Strategy identifies attempts by the People's Republic of China (PRC) to "refashion the Indo-Pacific region" as part of "the most comprehensive and serious challenge to U.S. national security."³⁷ In addition to strategic competition with the PRC, other core regional security interests include deterring and potentially defending against threats emanating from Russia and North Korea.³⁸ Overseas basing in the region is seen by some analysts and policymakers as a critical enabler of U.S. military operations in a potential great power conflict (particularly involving the PRC).³⁹ The Indo-Pacific is also the focus of a congressionally established set of defense investments and activities known as the Pacific Deterrence Initiative.⁴⁰

Figure 2. U.S. Overseas Bases in the Indo-Pacific

Source: CRS analysis of unclassified U.S. government documentation (including DOD budget documents, Base Structure Reports, official unit/installation webpages, press releases, Department of State documents, congressional testimony, and information provided by executive branch officials to CRS). Notes: The "Persistent" label describes a site that has been used consistently by DOD for at least 15 years and at which DOD exercises some degree of operational control. Bases in Guam and other U.S. territories are not depicted. Acronyms: AB=Air Base, CS=Communications Station, MCAS= Marine Corps Air Station, MCB= Marine Corps Base, MCI=Marine Corps Installation, NAF=Naval Air Facility, NB=Naval Base, NCS=Naval Communication Station, NB=Naval Base, NSF=Naval Support Facility, USAG=U.S. Army Garrison, USFA=U.S. Fleet Activity.

Europe

For the purposes of this report, Europe corresponds with the United States European Command (EUCOM) AOR. CRS identified 31 persistent bases and 19 other military sites to which DOD has access in the region.⁴¹ As of March 2024, approximately 67,200 active-duty servicemembers were permanently assigned to overseas bases in Europe, with the largest contingents assigned to locations in Germany (35,068), Italy (12,375) and the United Kingdom (10,058).⁴² However, as of June 2024, thousands of additional servicemembers are present in Europe on rotational deployments or other temporary assignments. In June 2024, the White House stated in a letter to congressional leaders that "approximately 80,000 United States Armed Forces personnel are assigned or deployed to North Atlantic Treaty Organization [NATO] countries in Europe, including those deployed to reassure our allies and to deter further Russian aggression."⁴³

U.S. forces assigned to overseas bases in Europe include Army ground units; Navy warships (including destroyers and an amphibious command ship, based in Spain and Italy); and Army, Navy, and Air Force aircraft (including rotary-wing, fighter, electronic attack, bomber, airlift, tanker, and other aircraft). EUCOM is headquartered in Stuttgart, Germany, although its three military service components maintain headquarters elements at other locations.⁴⁴

The U.S. military presence in Europe has increased in response to Russia's 2022 invasion of Ukraine. In June 2022, for example, a DOD press release claimed that, since the invasion, DOD had "deployed or extended over 20,000 additional forces to Europe in response to the Ukraine crisis, adding additional air, land, maritime, cyber, and space capabilities."⁴⁵ Prior to this surge, the Army maintained three brigade combat teams in Europe; since then, DOD has announced permanent forward stationing of a corps forward headquarters, a garrison command, a field support battalion, two squadrons of F-35s, an air defense artillery brigade headquarters, a short-range air defense battalion, a combat sustainment support battalion headquarters, and an engineer brigade headquarters.⁴⁶

U.S. basing in Europe is closely integrated with NATO activities and objectives. Many U.S. bases host NATO organizations and perform NATO-related functions, and every European host nation covered in this report (except Kosovo and Cyprus) is a NATO member.⁴⁷ According to the EUCOM Commander, Russia is the central security issue in the region, constituting a "formidable and unpredictable threat that will challenge U.S. and European interests for the foreseeable future."⁴⁸ Europe is also the focus of a set of U.S. defense investments and activities known as the European Deterrence Initiative (EDI).⁴⁹

Figure 3. U.S. Overseas Bases in Europe

Source: CRS analysis of unclassified U.S. government documentation (including DOD budget documents, Base Structure Reports, official unit/installation webpages, press releases, Department of State documents, congressional testimony, and information provided by executive branch officials to CRS). Notes: The "Persistent" label describes a site that has been used consistently by DOD for at least 15 years and at which DOD exercises some degree of operational control. Acronyms: AB=Air Base, NAS=Naval Air Station, NB=Naval Base, NB=Naval Base, NS=Naval Station, NSA=Naval Support Activity, NSF=Naval Support Facility, RAF=Royal Air Force, USAG=U.S. Army Garrison.

Middle East

For the purposes of this report, the Middle East corresponds with the U.S. Central Command (CENTCOM) AOR.⁵⁰ CRS identified eight persistent bases and 11 other military sites to which DOD has access in the Middle East.⁵¹ As of March 2024, approximately 5,400 active-duty servicemembers were permanently assigned to overseas bases in the Middle East, with the largest number assigned to locations in Bahrain (3,479).⁵² As of June 2024, thousands of additional servicemembers were present on rotational deployments or other temporary assignments. According to a June 2024 letter submitted by the Biden Administration to congressional leaders, this number includes approximately 3,813 servicemembers in Jordan and 2,321 servicemembers in Saudi Arabia.⁵³

As part of the U.S. response to the ongoing Israel-Hamas conflict, Houthi attacks on international shipping, and related geopolitical developments, DOD deployed additional servicemembers and units to the Middle East in 2023 and 2024. In October 2023, DOD announced the deployment of a carrier strike group, a Terminal High Altitude Area Defense battery, and additional Patriot battalions to the Middle East.⁵⁴ In December 2023, DOD announced the commencement of a multinational security initiative in the Red Sea (Operation Prosperity Guardian), and in January 2024 began launching air and missile strikes against Houthi targets in Yemen and alleged Iranian-linked militias in Iraq.⁵⁵ U.S. bases in Iraq, Syria, and Jordan have also been subjected to intermittent drone and missile attacks since October 2023.⁵⁶

CENTCOM is headquartered in Tampa, Florida, and operates a forward headquarters at Al Udeid Air Base in Qatar.⁵⁷ In March 2024, the CENTCOM commander identified three "lines of effort" for his command: "deterring Iran, countering violent extremist organizations, and competing strategically [i.e., with Russia and China]."⁵⁸ Compared to other regions, overseas basing in the Middle East (particularly Iraq and Syria) has been the subject of considerable recent controversy, both within the United States and internationally.⁵⁹

Figure 4. U.S. Overseas Bases in the Middle East

Source: CRS analysis of unclassified U.S. government documentation (including DOD budget documents, Base Structure Reports, official unit/installation webpages, press releases, Department of State documents, congressional testimony, and information provided by executive branch officials to CRS). Notes: The "Persistent" label describes a site that has been used consistently by DOD for at least 15 years and at which DOD exercises some degree of operational control. Acronyms: AB=Air Base, NSA=Naval Support Activity.

Africa

For the purposes of this report, Africa corresponds with the U.S. Africa Command (AFRICOM) AOR. CRS identified two persistent bases and seven other military sites to which DOD has access in the region. AFRICOM characterizes sites in the latter category as "posture locations," which it describes as locations with "minimal permanent U.S. presence, [that] have low-cost facilities and limited supplies … to perform critical missions and quickly respond to emergencies."⁶⁰ As of March 2024, approximately 1,150 active-duty servicemembers were permanently assigned to overseas bases in Africa, with the largest number assigned to locations in Djibouti (406).⁶¹ The number of active-duty servicemembers at overseas bases in Africa on rotational or other duty assignments is likely higher—for example, the Navy has reported the presence at Djibouti's Camp Lemonnier of "approximately 4,000 U.S., joint, and allied forces military and civilian personnel."⁶² AFRICOM is headquartered in Stuttgart, Germany.⁶³

AFRICOM is the newest geographic COCOM, and its AOR contains fewer permanently assigned servicemembers than that of any other COCOM. In his March 2024 Posture Statement before the Senate Armed Services Committee, the AFRICOM commander described violent extremist organizations and the expansion of PRC and Russian influence as the major threats to U.S. interests in the region.⁶⁴ Compared to basing in other regions, U.S. posture in Africa has been particularly dynamic in 2024. In January 2024, The Wall Street Journal reported that DOD was seeking to establish additional bases in coastal West Africa—specifically in Ghana, Côte d'Ivoire, and Benin—to support unmanned aerial surveillance operations.⁶⁵ And in March 2024, the Nigerien government revoked its Status of Forces Agreement with the United States, leading DOD to announce it would withdraw from the country (which had previously hosted two U.S. bases) by September 15, 2024.⁶⁶

Figure 5. U.S. Overseas Bases in Africa

Source: CRS analysis of unclassified U.S. government documentation (including DOD budget documents, Base Structure Reports, official unit/installation webpages, press releases, Department of State documents, congressional testimony, and information provided by executive branch officials to CRS). Notes: The "Persistent" label describes a site that has been used consistently by DOD for at least 15 years and at which DOD exercises some degree of operational control.

Central/South America and the Caribbean

For the purposes of this report, Central/South America and the Caribbean correspond with the U.S. Southern Command (SOUTHCOM) AOR, with one exception (the Bahamas—which hosts the U.S. Navy's Atlantic Undersea Test and Evaluation Center—is technically in the U.S. Northern Command AOR). CRS identified three persistent bases and three other military sites to which DOD has access in the region. As of March 2024, approximately 1,650 active-duty servicemembers were permanently assigned to overseas bases in Latin America and the Caribbean, with the largest number assigned to Cuba (616) and Honduras (365).⁶⁷ SOUTHCOM is headquartered in Doral, Florida.⁶⁸

Overseas basing in Central/South America and the Caribbean appears to mainly support counternarcotics operations, as well as some logistical and Research, Development, Test and Evaluation (RDT&E) activities.⁶⁹ In her 2024 Posture Statement before the House Armed Services Committee, the SOUTHCOM commander described the expansion of PRC and Russian influence and the activities of transnational criminal organizations as major regional threats to U.S. security.⁷⁰

Figure 6. U.S. Overseas Bases in Central/South America and the Caribbean

Source: CRS analysis of unclassified U.S. government documentation (including DOD budget documents, Base Structure Reports, official unit/installation webpages, press releases, Department of State documents, congressional testimony, and information provided by executive branch officials to CRS). Notes: The "Persistent" label describes a site that has been used consistently by DOD for at least 15 years and at which DOD exercises some degree of operational control. Acronyms: CSL=Cooperative Security Location.

Authorities and Management

Treaties and International Agreements

To acquire, lease, or otherwise obtain access to land and facilities for the purpose of overseas basing, the United States enters into diplomatic arrangements with foreign governments. Generally speaking, such arrangements take the form of bilateral agreements concluded between the executive branch and host-nation governments. These agreements may be referred to by a number of different names, including Status of Forces Agreements (SOFAs), Defense Cooperation Agreements (DCAs), Visiting Forces Agreements (VFAs), or Memoranda of Understanding (MOUs), and their scopes and provisions may vary widely. In some cases, the terms of such agreements—or even their existence—may not be public.

International agreements addressing basing rights are also typically separate from (though aligned with or governed by) any treaty that may exist between the United States and the country in question.⁷¹ Such agreements may also address related issues such as legal jurisdiction over U.S. personnel, tax and customs exemptions, or other issues. In addition to its bilateral basing agreements, the United States is party to a multilateral SOFA that applies to all members of the North Atlantic Treaty Organization (NATO).⁷²

The specific terms negotiated to govern land and infrastructure usage at overseas bases may vary by location. However, some practices and procedures are generally observed. According to DOD

The Department uses land, buildings, and other overseas facilities obtained through various international treaties and agreements negotiated by the Department of State. The Department purchases capital assets overseas with appropriated funds; however, the host country retains title to the land and capital improvements. Treaty terms generally allow the Department continued use of these properties until the treaties expire. In the event treaties or other agreements are terminated, use of the foreign bases is prohibited and losses are recorded for the value of any irretrievable capital assets. The settlement due to the United States or host nation is negotiated and takes into account the value of capital investments and may be offset by environmental cleanup costs, if applicable.⁷³

Relevant Statutory Authorities

Title 10, Chapter 159 of the United States Code (U.S.C.) governs DOD's acquisition, use, and disposal of real property, including overseas bases.⁷⁴ Relevant portions of this chapter include provisions authorizing the Secretary of Defense to lease land and structures in foreign countries (10 U.S.C. §2675) and requiring the Secretary of Defense to provide information to Congress regarding overseas base closures and realignments, as well as the status of overseas bases (10 U.S.C. §2687a).⁷⁵ In addition, 10 U.S.C. §2350k authorizes the Secretary of Defense to "accept contributions from any nation because of or in support of the relocation of elements of the armed forces from or to any location within that nation." These contributions may be used to pay numerous overseas basing costs, including those related to design and construction services, communications services, and the rental of office space.⁷⁶ Finally, 10 U.S.C. §2721 requires the Secretary of Defense to maintain records of, inter alia, the department's fixed property and installations "on both a quantitative and a monetary basis."⁷⁷

DOD Policy and Organizations

To manage its overseas bases, DOD has promulgated several issuances to establish policy and assign responsibilities. DOD Instruction 3000.12 establishes a Global Posture Executive Council (GPEC) to oversee global defense posture (which consists of the placement and organization of overseas bases, together with the positioning of forces and the structuring of international security agreements).⁷⁸ Pursuant to this instruction, several DOD positions are responsible for broad aspects of overseas basing, including the following:

• The Under Secretary of Defense for Policy (USD [P]). USD (P) "establishes policy and overall guidance for the governance of global defense posture."⁷⁹
• The Assistant Secretary of Defense for Strategy, Plans and Capabilities (ASD [SPC]) and the Director, Joint Staff (DJS). The ASD (SPC) and the DJS co-chair the GPEC and provide oversight, policy guidance, and assistance on posture matters.⁸⁰
• The Secretaries of the Military Departments and Military Service Chiefs. The Secretaries and Service Chiefs review combatant commander posture plans, support posture planning by requiring relevant cost data and estimates, and provide base operations support and management functions for enduring locations assigned to their Service(s).⁸¹
• The Combatant Commanders (CCDRS). The CCDRS evaluate the adequacy of current posture to support their campaign plans and associated objectives, develop a theater or functional posture plan, and coordinate requirements with other stakeholders.⁸²

The GPEC also includes representation from numerous other DOD and U.S. government organizations.⁸³

In addition to DOD Instruction 3000.12, DOD Directive 3000.10 Contingency Basing Outside the United States establishes policy and assigns responsibilities specifically for overseas contingency basing.⁸⁴

On a day-to-day basis, each military department (MILDEP) manages its overseas bases through its own organizational structures, policies, and programs.⁸⁵ From a regional and joint perspective, the six geographically organized COCOMs provide oversight and theater-level direction of the strategic and operational dimensions of DOD's overseas basing posture.

Issues for Congress

Resourcing Overseas Basing

Congress's most direct role in overseas basing is to consider whether or not to make funds available to establish and maintain military bases. Congress appropriates funds to military construction (MILCON) accounts to pay for the construction or expansion of base facilities and certain operation and maintenance (O&M) accounts to pay for base operations, maintenance, and related support activities.⁸⁶ Congress also funds appropriations accounts that support other aspects of DOD's global defense posture (e.g., overseas deployments) that may be considered part of overseas basing. Congress faces questions that include (1) whether to appropriate funds for overseas basing-related activities (and, if so, how much); and (2) whether DOD's execution of overseas basing-related appropriations meets congressional intent.

Total Overseas Basing Costs

Other than for military construction projects, DOD's budget documents do not typically break down spending by geographical location. As a result, it can be difficult to accurately determine the total costs of overseas basing, or identify costs by region or site. There are also numerous ways to define the costs of overseas basing, each of which could yield different figures. For example, one definition could include only spending associated with the real property and physical infrastructure (e.g., buildings, structures) occupied by overseas bases. Another could include spending associated with permanently stationing DOD servicemembers, weapons systems, and other assets overseas.⁸⁷ A third could include the costs of rotational deployments, exercises, and similar activities conducted at overseas bases. Because MILCON and certain O&M accounts (i.e., the Base Operations Support, or BOS, and Facilities Sustainment, Restoration, and Modernization, or FSRM, subactivity groups) are common to all three definitions, these appropriations are discussed in more detail in the "MILCON " and "Operation & Maintenance (O&M) " sections of this report.

To estimate total overseas basing-related MILCON spending for FY2023, CRS reviewed DOD's FY2024 "Military Construction, Family Housing, and Base Realignment and Closure Program (C-1)" budget submission. The total obligation authority enacted for FY2023 for MILCON projects associated with combatant commands outside the continental United States (OCONUS) was $5.355 billion.⁸⁸

In FY2023, DOD provided two different estimates of non-MILCON overseas basing costs as part of its annual budget submission. The first is the "overseas cost summary" which "identifies the amounts necessary for payment of all personnel, operations, maintenance, facilities, and support costs for all [DOD] overseas military units and the costs of supporting all dependents who accompany DoD personnel outside of the United States."⁸⁹ This estimate—which includes some funding for procurement and research and development—puts the total cost for overseas operations activities at $27.8 billion.⁹⁰

In the same document, DOD provided an estimate of $31.7 billion for enacted appropriations to support overseas operations in FY2023.⁹¹

Although the figures reported by DOD may serve as a useful indicator, they may not include all of the non-MILCON spending associated with overseas basing, as they may exclude costs related to contingency operations, rotational deployments or training exercises involving units ordinarily based in the United States.

Independent researchers have also provided alternative estimates for the total cost of U.S. overseas basing. One 2021 study by the Quincy Institute for Responsible Statecraft estimated the total cost to be $55 billion annually.⁹² A RAND Corporation report from 2013 analyzed the Air Force's overseas operations and concluded that the costs to maintain the Air Force's overseas force structures and installations overseas rather than in the United States was roughly $3.4 billion, which amounted to about 2% of the Air Force's total budget at the time of the study.⁹³

Some of DOD's overseas basing costs may be defrayed by financial or in-kind contributions from foreign governments. For further discussion, refer to this report's "Burden Sharing" section below.

MILCON Appropriations

MILCON appropriations fund the planning, design, and building of physical infrastructure at DOD installations.⁹⁴ In FY2023, Congress appropriated a total of $13.593 billion for specific MILCON projects worldwide.⁹⁵ Of that total, $5.355 billion—or 39%—went to locations in overseas combatant commands. Congress may consider whether this total is appropriate to meet U.S. strategic and operational objectives; depending on its assessment, Congress may consider increasing, decreasing, or keeping constant annual MILCON appropriations.

Aside from the question of how much total funding to appropriate for overseas MILCON projects, Congress may also consider where and how MILCON funds are spent. As Figure 7 shows, the regional distribution of MILCON funding has varied over the past 15 years. The proportion of spending in the CENTCOM AOR—which accounted for a plurality of overseas MILCON projects by financial value for several years during the late 2000s and early 2010s—has decreased considerably, for instance, while projects in the INDOPACOM AOR have accounted for the majority of overseas MILCON spending for the past four fiscal years.⁹⁶ This change likely reflects strategic developments; as DOD's focus has shifted from the Global War on Terror to great power competition, the allocation of MILCON funds has changed to reflect the increased importance of Europe and the Indo-Pacific vis-à-vis the Middle East. Congress may consider whether the current distribution of MILCON funds adequately reflects the balance of its regional priorities and may determine whether or not to modify the geographical or functional allocation of such appropriations.

Figure 7. DOD Military Construction Spending by Region, FY2007-FY2023 Total Obligational Authority by COCOM AOR

Source: CRS analysis of DOD Under Secretary of Defense (Comptroller) Military Construction, Family Housing and Base Realignment and Closure Program (C-1) documents, FY2015-FY2023, https://comptroller.defense.gov/Budget-Materials/. Notes: This figure excludes MILCON accounts that are not associated with specific locations in DOD budget documents (e.g., DOD-wide, Planning and Design accounts, Family Housing Operations and Maintenance, Base Realignment and Closure Account, Family Housing Improvement Fund). Data also excludes MILCON projects in the continental United States/elsewhere in the NORTHCOM AOR.

Operation & Maintenance (O&M) Appropriations

Two subactivity groups (SAGs) within the operation and maintenance (O&M) appropriation directly fund support and maintenance of military bases, including those overseas: Base Operations Support (BOS) and Facilities Sustainment, Restoration, and Management (FSRM). Unlike MILCON, these elements of O&M spending are not typically disaggregated by location or installation; CRS is therefore unable to perform a geographic analysis of Base Operations Support or Facilities Sustainment, Restoration, and Modernization spending.

The FSRM SAGs support activities such as major repairs to buildings and structures, the restoration of damaged facilities, and limited facility alterations. In FY2023, Congress appropriated approximately $17.419 billion for FSRM across DOD, with the active-component Army (approximately $5.147 billion), the active-component Air Force (approximately $4.391 billion), the active-component Navy (approximately $3.956 billion), and the active-component Marine Corps ($1.342 billion) receiving the largest amounts, respectively.⁹⁷ These FSRM figures include domestic and overseas costs.⁹⁸

The BOS SAGs fund "installation services," including facilities operations (e.g., utilities, engineering services), logistics operations (e.g., food services, vehicle management), community services (e.g., morale, welfare, and recreation programs), security services (e.g., installation law enforcement, physical security), information technology services (e.g., telephones, network services), and related activities.⁹⁹

Congress may consider whether these totals are adequate to meet its basing objectives and priorities, and adjust the level of annual appropriations as necessary. For example, if Congress assesses that the tempo of overseas base operations is increasing, it may decide to increase appropriations for BOS or FSRM activities; conversely, if Congress determines that there is less need for such operations, it may hold these appropriations constant or decrease them. Additionally, if Congress determines it lacks sufficient information about where these O&M funds are actually being spent, it may require DOD to provide more information as to the geographic distribution of overseas basing-related O&M spending.

Managing Relations with Host Nations

The strategic value of an overseas base depends in large part on good U.S. relations with the base's host nation—that is, the nation whose territory the base occupies. With certain limited exceptions, the United States does not typically maintain overseas bases without the agreement of the host nation (of the areas covered by this report, only sites in Syria and Guantanamo Bay in Cuba are used without host-nation consent).¹⁰⁰

Congress faces several related questions, such as whether or not the executive branch is developing and maintaining relations with host nations that adequately support U.S. national strategy and congressional policy priorities; how the presence and operation of U.S. forces may affect regional security dynamics; how the behavior of adversaries may affect the security of U.S. servicemembers and partner forces; and what the costs and consequences of alternative approaches may be.

Negotiating Basing Rights

As described in the "Authorities and Management" section of this report, the United States relies on a variety of diplomatic understandings—mainly, but not exclusively, bilateral executive agreements—to establish and govern overseas basing rights.

As a result, the executive branch—especially DOD and the Department of State—is mainly responsible for negotiating the terms and conditions of U.S. overseas basing rights. However, Congress may exercise oversight over the terms and implementation of these executive agreements by requiring reports, holding hearings, expressing the sense of Congress, or issuing direction to DOD through legislation. Additionally, Congress may choose to legislate a statutory role for itself in the negotiation or approval of basing agreements, if Members determine that congressional priorities are not adequately reflected in the executive branch's handling of such relations (for example, Congress could require notification or approval before the conclusion of any new basing agreements or it could link U.S. financial expenditures on basing in certain countries to specific burden sharing, force protection, or other considerations). For basing arrangements that require congressional action or approval (for example, those established by treaties, or congressionally enacted agreements like the Compacts of Free Association), Congress may consider which kinds of terms and conditions are most advantageous to the national interest.

Reliable Access and Political Risk

Another issue Congress may consider is reliability of U.S. access to overseas bases, which may be understood as a function of political risk.

Because nearly all overseas bases are ultimately subject to foreign sovereignty, DOD's ability to use these locations may be affected by political developments beyond U.S. control.¹⁰¹ Instances of host nations altering the terms of—or outright revoking—U.S. basing rights have occurred several times in recent history, and can create strategic and operational problems for military planners. The presence of U.S. forces in a country may be the subject of political controversy, and ensuing disputes may lead to abrupt and substantial policy or security changes.

In some cases, host-nation governments have unexpectedly decided to expel U.S. forces (as in France during the mid-1960s, when French president Charles de Gaulle informed the United States that existing basing agreements between the two countries no longer obtained, ending two decades of U.S. military presence).¹⁰² On other occasions, host-nation governments have moved to restrict the ways in which DOD may use bases located in their territories (for example, in 2003 the Turkish government blocked the U.S. military from using Incirlik Air Base for combat operations against Iraq).¹⁰³ Another possibility is that a new government may come to power and radically change its country's approach to U.S. basing (as happened recently in Niger, when—following a 2023 coup d'état—the new military junta unilaterally cancelled the existing SOFA with the United States, compelling the withdrawal of U.S. forces and the abandonment of two bases).¹⁰⁴

Congress may also consider the question of access during periods of protracted or intense conflict. Host nations may be unwilling to allow the United States to use bases in their territories, for fear it could expose them to attack or involve them in a war they would rather avoid. Depending on the nature of the conflict, it is possible that even treaty allies may decide to restrict or prohibit the use of their territories by the U.S. military. For example, senior officials in the Philippines—a U.S. treaty ally that hosts bases seen by many analysts as relevant to a potential U.S.-China conflict—have stated that, in the event of a regional war, their government may bar U.S. forces from using Philippine territory to conduct or support combat operations against third parties.¹⁰⁵

Congress may consider the degree to which the United States can depend on host nations—particularly countries with histories of instability or anti-American political traditions—to grant or maintain basing rights on sufficiently favorable terms. Congress may also consider whether or not DOD adequately accounts for this kind of political risk in its strategic and operational planning. If Congress identifies issues with DOD's approach, it could require new plans, strategies, or reports to address these risks. If there are particular countries of concern, Congress could also prohibit the development of new basing arrangements with these countries, or introduce specific requirements to govern basing in these locations.

Burden Sharing

Another issue is the degree to which a host nation may contribute to the upkeep and support of U.S. forces and facilities at bases in its territory (often referred to as burden sharing). The question of whether host nations are paying enough to support U.S. basing has been a contentious political issue since the early Cold War. Some critics and policymakers have alleged that host-nation governments contribute less than they should to defray the costs of America's military presence in their countries, especially considering that (1) some host nations (such as Germany, Japan, and South Korea) are high-income countries; and (2) U.S. basing provides security and further economic benefits.¹⁰⁶ Others have argued that host nations generally contribute an appropriate amount to support U.S. basing and that the United States benefits as much as host nations from its global defense posture.¹⁰⁷

DOD annually reports at least some of the burden sharing contributions it receives from host nations. According to the most recent report, in FY2023, the United States received a total of $714.2 million in burden sharing contributions from five countries (Kuwait, Japan, South Korea, Saudi Arabia, and Poland).¹⁰⁸

Despite this information, as noted above, the structure of DOD's budget presents difficulty in determining the costs associated with overseas basing. CRS is unable to conclusively determine how much of DOD's total overseas basing costs are covered by host-nation contributions. The Government Accountability Office (GAO) recently attempted to evaluate burden sharing for major U.S. allies in a 2021 report examining, inter alia, the contributions of the Japanese and South Korean governments to supporting the U.S. military presence in their respective countries. GAO found that, between FY2016 and F2019, Japan and South Korea provided $12.6 billion and $5.8 billion, respectively, in "direct financial support" to pay costs—such as "labor, construction, and utilities"—associated with U.S. overseas basing.¹⁰⁹ In the Japanese case, host-nation contributions amounted to 60.2% of the value of DOD obligations associated with the U.S. military presence over the same period. In the South Korean case, host-nation contributions amounted to 43.3% of the value of DOD obligations associated with the U.S. military presence over the same period.¹¹⁰ According to media reports, the government of Germany—which hosts the second largest number of permanently assigned U.S. servicemembers, behind Japan—reported contributing $270 million to U.S. basing costs between 2012 and 2019.¹¹¹ As another example, Qatar is reportedly making investments in DOD's Al Udeid Air Base to support the continuation of the U.S. military presence there.¹¹²

If Congress is concerned that the current degree of burden sharing is insufficient, a number of options are available. Congress could seek more information on foreign contributions to U.S. basing costs by requiring DOD to provide data on such contributions, commissioning independent reports, or holding hearings. If Congress determines that host nations are not paying enough, it could condition appropriations for certain overseas basing-related expenditures on relevant host nation(s) meeting certain contribution thresholds, require the revision of existing basing arrangements, or prohibit DOD from basing forces in countries that fail to contribute sufficiently to U.S. basing costs.

Aligning Overseas Basing with Strategic and Operational Priorities

Although the executive branch has long exercised the lead role in determining national military strategy and managing the U.S. military's overseas basing posture, Congress may shape executive branch decision-making and exercise oversight in a number of ways. It may assess whether the placement and organization of overseas bases adequately supports U.S. interests and strategic goals, for instance, and consider whether current posture meets the requirements of new operational concepts, weapons systems, or other warfighting developments.

Overseas Basing and National Strategy

Since the early days of the Cold War, overseas basing has played a significant role in national strategy.¹¹³ Its principal contribution has been to enable the forward presence (sometimes also referred to as "forward deployment" or "forward posture") of U.S. forces, which DOD officials have claimed deters potential adversaries from attacking the United States and its allies and partners.¹¹⁴ In addition to enabling military operations, overseas bases may signal that the U.S. government views particular areas as important to the national interest, as well as communicate U.S. commitment to the defense and support of regional allies and partners. Overseas basing may also entail risks to U.S. servicemembers and assets (for example, U.S. forces based in Iraq, Syria, and Jordan have been attacked by armed groups dozens of times in 2023 and 2024).¹¹⁵

Evidence for the strategic effects of DOD's current and recent global basing posture varies. A 2013 report on overseas basing by the RAND Corporation identified three major strategic benefits (contingency responsiveness, deterrence and assurance, and security cooperation) and three major strategic risks (political risks, operational risks, and violent extremism risks).¹¹⁶

The deterrent effect of overseas basing is difficult to measure. Some researchers have claimed that "some types of U.S. forward posture do generally have deterrent effects when deployed near the ally or partner state to be defended," particularly those which are relatively immobile (e.g., heavy ground forces).¹¹⁷ Other analysts have posited that "the deterrence value of overseas military bases is frequently exaggerated," explaining U.S. strategic successes by reference to geopolitical developments other than the forward military presence such bases enable.¹¹⁸

Among those who attribute a positive strategic effect to overseas basing, some argue that the benefits of an expansive posture outweigh both the risks and the costs. On this view, a restrained global or regional posture could undermine DOD's ability to project force in distant regions and respond to potential contingencies.¹¹⁹ Some also claim that an insufficiently robust basing posture will signal to potential aggressors that a particular area is unimportant to U.S. national interests—or that U.S. commitment to regional allies and partners is tenuous or uncertain—and thus make conflict more likely.¹²⁰

Alternatively, some maintain that an overly expansive basing posture actually increases the risk of conflict, because it creates or intensifies adversary perceptions of U.S. threats.¹²¹ This line of argument is sometimes connected to what international relations theorists call the security dilemma (a phenomenon in which states' attempts to improve their security cause other states to feel less secure and improve their own military capabilities, precipitating a cycle that can end in armed conflict). Some proponents of this perspective claim that U.S. basing could undermine regional or global stability by provoking rival counter-moves.¹²² Others have emphasized the costs for U.S. servicemembers, arguing that overseas basing in conflict-prone areas unnecessarily exposes DOD servicemembers to danger without meaningfully contributing to national security.¹²³

Congress may assess the strategic consequences of DOD's current overseas basing posture, and consider whether or not modifications to that posture—such as increasing or reducing the number of overseas bases—would advance U.S. interests.

Overseas Basing and Distributed Operational Concepts

In addition to broader strategic considerations, Congress may also consider the degree to which overseas basing posture aligns with DOD's own warfighting plans and requirements. Over the past five years, the Air Force, Army, Navy, and Marine Corps have all developed concepts for more distributed and diversified combat and logistical operations. The Air Force's Agile Combat Employment (ACE), the Army's Multi-Domain Operations (MDO), the Navy's Distributed Maritime Operations (DMO), and the Marine Corps' Expeditionary Advanced Basing Operations (EABO) all represent attempts to reduce the vulnerability of air, naval, and ground forces and increase their effectiveness against an adversary able to credibly disrupt, contest, or deny U.S. control of the battlespace.¹²⁴ The services' new concepts break from previous planning paradigms, and their implementation may require a different approach to basing, one in which large, permanent, and concentrated bases are supplemented by—or even replaced with—smaller, temporary, or distributed facilities.

Of all of these operational concepts, ACE may potentially entail the most significant basing changes. The Air Force describes ACE as a means of "shift[ing] operations from centralized physical infrastructures to a network of smaller, dispersed locations that can complicate adversary planning and provide more options for joint force commanders."¹²⁵ Some analysts have characterized this as a 'hub-and-spokes' approach, with an enduring location (e.g., an existing U.S. or allied airbase) serving as a hub for a number of contingency locations (e.g., civilian airports, austere airstrips) between which aircraft can be shifted and from which sorties may be launched. According to its proponents, ACE will thereby minimize vulnerability to kinetic attack (particularly in regions like the Indo-Pacific and Europe, where potential adversaries possess highly capable ballistic missile arsenals) and maximize the effectiveness of U.S. and allied airpower.¹²⁶

Although the basing implications of the Army's MDO and the Navy's DMO are less sweeping, both concepts envision decreasing the concentration of logistics and supply infrastructure. As part of MDO, the Army seeks to "disperse deployment and sustainment," partly through "dispersed supply nodes operated by forward presence units;" while the Navy's vision of a larger, more dispersed fleet operating over a wider area could increase the need for forward, distributed logistics and maintenance sites (including what the Navy terms "distributed expeditionary shore infrastructure" to provide forward damage repair, mobile construction, cargo handling, and medical services).¹²⁷ From a ground-forces perspective, the Marine Corps' EABO similarly envisions the "employment of mobile, low-signature, persistent … naval expeditionary forces from a series of austere, temporary locations ashore or inshore within a contested or potentially contested maritime area."¹²⁸

The implementation of these concepts may require changes to DOD's overseas basing posture, resourcing, and management. They may also entail complex diplomatic negotiations with current or potential host nations. Congress may consider the costs and benefits of a more distributed approach to overseas basing, assess the extent to which these concepts are being implemented, and consider whether or not changes to annual defense appropriations are necessary to successfully execute these plans and concepts.

Appendix A. U.S. Overseas Basing by Country

This appendix provides more detailed information on U.S. overseas basing in individual countries. The list below provides summaries of basing arrangements in 51 host nations (sorted by region). In addition, Appendix B provides a comprehensive list of all overseas bases covered by this report.

Indo-Pacific

U.S. overseas basing in the Indo-Pacific is established and governed by bilateral executive agreements between the United States and regional governments, as well as congressionally approved Compacts of Free Association (in the cases of the Marshall Islands, Micronesia, and Palau). Most of the U.S. servicemembers permanently assigned to this region are stationed at persistent bases in Japan and South Korea. Over the past 15 years, DOD has established rotational basing arrangements in Australia, the Philippines, and elsewhere.

Australia

The United States maintains Marine Rotational Force-Darwin at Royal Australian Air Force (RAAF) Base Darwin and Robertson Barracks between April and October of each year, and rotationally deploys combat aircraft at RAAF Base Tindal and other Australian military sites. U.S. Virginia-class submarines are to be rotationally based near Perth beginning in the mid-to-late 2020s.¹²⁹ In addition, the United States and Australia jointly operate the Naval Communication Station Harold E. Holt and Joint Defence Facility Pine Gap sites.¹³⁰

According to the Defense Manpower Data Center (DMDC), approximately 732 active-duty servicemembers were permanently assigned to Australia as of March 2024 (this figure does not include servicemembers on temporary duty or rotational assignments).¹³¹

British Indian Ocean Territory (Diego Garcia)

The United States maintains Naval Support Facility (NSF) Diego Garcia in the British Indian Ocean Territory (commonly referred to as Diego Garcia), an overseas dependency of the United Kingdom.¹³² NSF Diego Garcia provides logistical support for forces operating in and around the Persian Gulf and Indian Ocean, and hosts a maritime pre-positioning squadron as well as detachments from the U.S. Fleet and Industrial Supply Center, Air Mobility Command, Pacific Air Force, and the 21^st and 22^nd Space Operations Squadrons.¹³³

According to DMDC, approximately 223 active-duty servicemembers were permanently assigned to Diego Garcia as of March 2024.¹³⁴

Japan

Japan hosts large U.S. Army, Navy, Marine Corps, and Air Force bases, including Camp Zama, Fleet Activities Yokosuka, Marine Corps Air Station Iwakuni, Yokota Air Base, and Misawa Air Base.¹³⁵ These sites are used to base and support a wide variety of Army ground units, Navy vessels (including an aircraft carrier, destroyers, cruisers, and amphibious assault ships), and Army, Navy, Marine Corps, and Air Force aircraft (including fighter, electronic attack, command and control, tiltrotor, tanker, and airlift aircraft). DOD also uses defense infrastructure in Japan to detect and intercept missile threats, maintain and repair surface warships and submarines, and conduct training and exercises.¹³⁶

The Japanese prefecture of Okinawa, located about 400 miles southwest of Japan's four main islands, hosts Army, Marine Corps, and Air Force bases, including Army Garrison Okinawa, Marine Corps Base Camp Butler, and Kadena Air Base. These sites are used to base and support Marine Corps ground units (including the III Marine Expeditionary Force, the Corps' largest combat unit stationed overseas) and Marine Corps and Air Force fighter, tilt-rotor, rotary wing, airlift, and aerial refueling aircraft. DOD also uses Okinawa to conduct training and exercises specific to jungle environments and to store fuel.¹³⁷ DOD installations on Okinawa represent the closest U.S.-operated bases to Taiwan and the South China Sea, both possible operational areas in a potential conflict with the PRC. Pursuant to a bilateral agreement between the United States and Japan, DOD has committed to relocating approximately 9,000 Marines from Okinawa to Guam (and other locations outside Japan) beginning in 2024.¹³⁸

According to DMDC, approximately 54,774 active-duty servicemembers were permanently assigned to Japan as of March 2024.¹³⁹

Republic of Korea (South Korea)

The Republic of Korea (ROK, or South Korea) hosts Army, Navy, Marine Corps, and Air Force bases, including Camp Humphreys, Fleet Activities Chinhae, Marine Corps Installation Camp Mujuk, and Osan Air Base. These sites are used to base and support Army units (including the 2^nd Infantry Division/ROK-U.S. Combined Division) and Air Force fighter, reconnaissance, and attack aircraft. Pursuant to a 2004 U.S.-ROK agreement, DOD installations are mainly concentrated around two "hubs": the first centers on the city of Pyeongtaek and includes Camp Humphreys and Osan Air Base, while the second centers on Daegu and includes USAG-Daegu, Fleet Activities Chinhae, and MCI Camp Mujuk.¹⁴⁰ Uniquely, the U.S. and ROK militaries share operational control of their forces in the country through the ROK/U.S. Combined Forces Command, which acts as a unified, binational "warfighting headquarters."¹⁴¹ U.S. basing posture in South Korean is primarily organized around deterring and resisting potential DPRK aggression.

According to DMDC, approximately 24,234 active-duty servicemembers were permanently assigned to South Korea as of March 2024.¹⁴²

The Marshall Islands, Micronesia, and Palau (Freely Associated States)

The United States maintains Army Garrison Kwajalein Atoll (which hosts the Ronald Reagan Ballistic Missile Defense Test Site) in the Marshall Islands, and is currently constructing a radar site in Palau.¹⁴³ The U.S. military presence in the Freely Associated States is governed by the Compacts of Free Association, which establish unique political relationships between the United States and each FAS government.¹⁴⁴ Per the terms of the Compacts, the United States has responsibility for the defense of the FAS, as well as basing and access rights within FAS territories.

According to DMDC, approximately 101 active-duty servicemembers were permanently assigned to as the Freely Associated States of March 2024.¹⁴⁵

The Philippines

The United currently has access to nine Philippine-operated defense sites under the terms of the 2014 U.S.-Philippines Enhanced Defense Cooperation Agreement (EDCA).¹⁴⁶ Per the EDCA, U.S. access to these sites is authorized "on a rotational basis, as mutually determined;" authorized activities U.S. forces may conduct include "security cooperation exercises; joint and combined training activities; humanitarian assistance and disaster relief activities; and such other activities as may be agreed upon."¹⁴⁷

According to DMDC, approximately 310 active-duty servicemembers were permanently assigned to the Philippines as of March 2024.¹⁴⁸

Singapore

The United States maintains a small permanent presence at its Navy Region Center Singapore, which coordinates logistical support for visiting surface warships, and also conducts ongoing rotational deployments of Littoral Combat Ships and P-8 Poseidon aircraft.¹⁴⁹ Facilities to which the U.S. military has access include Changi Naval Base and Sembawang shipyard, while Paya Lebar Air Base may host U.S. servicemembers and aircraft on a rotational basis.¹⁵⁰ Basing in Singapore is governed by a number of executive agreements.¹⁵¹

According to DMDC, approximately 229 active-duty servicemembers were permanently assigned to Singapore as of March 2024.¹⁵²

Other Indo-Pacific Bases

In addition to the locations described above, DOD may have access to a number of other bases in the region. For example, U.S. forces used a number of Thai military bases on a rotational basis during the Global War on Terror (e.g., U-Tapao Royal Thai Navy Air Field), and in 2023 DOD concluded an agreement with Papua New Guinea to allow U.S. forces access to six airports and seaports in the country.¹⁵³ U.S. Navy vessels also routinely conduct visits at a wide array of Indo-Pacific regional ports.¹⁵⁴

Europe

U.S. overseas basing in Europe is established and governed by bilateral executive agreements between the United States and regional governments, as well as the multilateral NATO SOFA (except for Cyprus and Kosovo, all of the countries included in this section are members of NATO).¹⁵⁵ Most of the U.S. servicemembers permanently assigned to Europe are stationed at persistent bases in Germany, Italy, and the United Kingdom. Over the past ten years (and particularly following Russia's 2022 invasion of Ukraine), the United States has established a military presence in many Eastern European countries. In addition, DOD frequently conducts rotational deployments in Europe involving tens of thousands of servicemembers. To reflect these deployments, throughout this section CRS has supplemented DMDC-provided figures—which only include permanently assigned servicemembers—with reporting or estimates from other sources, as appropriate.

Belgium

DOD maintains several administrative sites in Belgium, which are overseen by U.S. Army Garrison Benelux.¹⁵⁶ U.S. basing in Belgium mainly supports NATO activities, including support for coordination with the nearby NATO headquarters in Belgium (the Supreme Headquarters Allied Powers Europe, or SHAPE, is located in Casteau near Mons, Belgium).¹⁵⁷

According to DMDC, approximately 1,106 active-duty servicemembers were permanently assigned to Belgium as of March 2024.¹⁵⁸

Bulgaria

The United States currently has access to four military facilities in Bulgaria under the terms of a 2008 cooperative security agreement.¹⁵⁹ A bilateral agreement between Bulgaria and the U.S. also permits up to 2,500 U.S. servicemembers to enter the country for military training.¹⁶⁰ In March 2022, the U.S. Army deployed a Stryker armored-vehicle infantry company to support a NATO battle group in the country, and U.S. Navy warships have made recurring port visits to Varna.¹⁶¹

DOD's FY2023 Base Structure Report identifies the Novo Selo Training Area, and Graf Ignatievo Air Base as DOD facilities, and Congress has appropriated funds for MILCON projects at these bases.¹⁶²

According to DMDC, approximately 19 active-duty servicemembers were permanently assigned to Bulgaria as of March 2024.¹⁶³

Cyprus

The U.S. Air Force regularly deploys servicemembers and assets to RAF Akrotiri, a British overseas base in Cyprus.¹⁶⁴ Although little information concerning the U.S. presence in Cyprus is publicly available, DOD's FY2023 Base Structure Report lists RAF Akrotiri as a U.S. site, and in 2020 the Air Force initiated a $27 million MILCON project at RAF Akrotiri. ¹⁶⁵

In November 2023, five U.S. servicemembers died in a helicopter crash off the coast of Cyprus; they were reportedly special operations troops conducting a refueling training mission.¹⁶⁶

According to DMDC, approximately 11 active-duty servicemembers were permanently assigned to Cyprus as of March 2024.¹⁶⁷

Estonia

DOD regularly conducts exercises in and rotational deployments to Estonia.¹⁶⁸ In May 2023, for instance, the U.S. Air Force sent F-22 Raptors to Ämari Air Base in Estonia, with the intent to "to deter aggression in the Baltic Sea region," and the U.S. Marine Corps conducted training exercises in Estonia.¹⁶⁹

Between FY2015 and FY2018, DOD received about $45 million in MILCON appropriations for infrastructure improvements at Ämari Air Base.¹⁷⁰

According to DMDC, approximately 20 active-duty servicemembers were permanently assigned to Estonia as of March 2024.¹⁷¹ In September 2023, media report about 600 U.S. servicemembers in Estonia.¹⁷²

Finland

The United States does not currently maintain a military presence in Finland, but in December 2023, the United States and Finland signed a Defense Cooperation Agreement that grants DOD access to 15 Finnish military sites.¹⁷³

According to DMDC, approximately 32 active-duty servicemembers were permanently assigned to Finland as of March 2024.¹⁷⁴

Germany

Since the end of World War II, Germany has hosted a large, enduring U.S. military presence, including several large Army and Air Force bases.

The Army's bases in Germany are grouped into five garrisons: U.S. Army Garrison Ansbach; U.S. Army Garrison Bavaria (which includes the Grafenwoehr Training Area and the Hohenfels Training Area, DOD's largest permanent training areas in the region); U.S. Army Garrison Rheinland-Pfalz; U.S. Army Garrison Stuttgart; and U.S. Army Garrison Wiesbaden.¹⁷⁵ (Each Army garrison may encompass multiple constituent sites—sometimes distributed across a wide area—that are not listed individually in this report). Army assets assigned to locations in Germany include a combat aviation brigade and a field artillery brigade.¹⁷⁶

The U.S. Air Force in Germany includes a wing headquarters and a squadron of fighter aircraft (F-16C/D Fighting Falcons) at Spangdahlem Air Base, as well as an air mobility wing headquarters and reportedly a squadron of transport aircraft (C-130J-30 Hercules) at Ramstein Air Base.¹⁷⁷ Germany also hosts Landstuhl Regional Medical Center, DOD's largest overseas medical facility.¹⁷⁸

According to DMDC, approximately 35,068 active-duty servicemembers were permanently assigned to Germany as of March 2024.¹⁷⁹

Greece

The United States maintains Naval Support Activity (NSA) Souda Bay on the Greek island of Crete, and frequently conducts exercises in and rotational deployments to the country.¹⁸⁰

NSA Souda Bay includes one of the Mediterranean's few deep-water ports, an all-weather airfield, and refueling and resupply facilities.¹⁸¹ U.S. warships also conduct port visits to Piraeus (near Athens), and the ports of Thessaloniki and Alexandroupolis support DOD logistical operations in southeastern Europe, including activities related to security assistance for Ukraine.¹⁸²

The U.S. Air Force has conducted air mobility operations training exercises at Larissa Air Base.¹⁸³ DOD has also reportedly used Larissa to support MQ-9 Reaper drones for Intelligence, Surveillance and Reconnaissance (ISR) missions.¹⁸⁴ Stefanovikeio Air Base also serves as a rotational site for a U.S. Army aviation task force.¹⁸⁵

According to DMDC, approximately 402 active-duty servicemembers were permanently assigned to Greece as of March 2024.¹⁸⁶

Greenland (Denmark)

The United States maintains Pittufik Space Base (formerly known as Thule Air Base) in Greenland, an autonomous territory of Denmark. Pittufik is DOD's northernmost overseas base, and supports space domain awareness and surveillance, missile warning and defense, and related functions.¹⁸⁷

According to DMDC, approximately 135 active-duty servicemembers were permanently assigned to Greenland as of March 2024.¹⁸⁸

Hungary

DOD conducts rotational deployments to and exercises in Hungary. In July 2021, U.S. European Command and Hungarian Defense Force leaders signed agreements designating Kecskemét Air Base and Pápa Air Bases as "agreed facilities and areas."¹⁸⁹ In July 2023, the U.S. Air Force deployed two rescue squadrons to Papa Air Base for an exercise, and in May 2023, soldiers from the 101^st Airborne Division were deployed at Camp Croft near Veszprém.¹⁹⁰

In FY2023, DOD initiated a $71 million project at Papa Air Base to install a Deployable Air Base System.¹⁹¹

According to DMDC, approximately 84 active-duty servicemembers were permanently assigned to Hungary as of March 2024.¹⁹²

Iceland

Iceland hosts U.S. maritime patrol and reconnaissance aircraft at Keflavik Air Base.¹⁹³ Since FY2017, Congress has appropriated over $185 million for MILCON projects at Keflavik.¹⁹⁴

According to DMDC, approximately three active-duty servicemembers were permanently assigned to Iceland as of March 2024.¹⁹⁵ Air Force and Navy units have deployed to Keflavik for exercises and temporary duties, including a detachment of Navy anti-submarine aircraft.¹⁹⁶

Italy

Since the end of World War II, Italy has hosted a large, persistent U.S. military presence, including several large Army, Navy, and Air Force bases.

U.S. Army Garrison Italy, with a headquarters at Camp Ederle in Vicenza, is home to an airborne infantry brigade combat team that serves as a rapid response force for European, African, and Middle Eastern locations.¹⁹⁷

Aviano Air Base hosts two F-16 fighter squadrons and a helicopter rescue squadron.¹⁹⁸

Naval Support Activity Naples hosts the headquarters for U.S. Naval Forces Europe and Africa and the U.S. 6^th Fleet. The U.S. 6^th Fleet Blue Ridge-class command and control ship, the USS Mount Whitney (LCC 20), is homeported in near Naples at Gaeta.¹⁹⁹ Naval Air Station Sigonella in Sicily hosts a rotational presence of Navy P-8A Poseidon anti-submarine aircraft, as well as a squadron of Marine Corps MV-22 Osprey tilt-rotor aircraft.²⁰⁰ The Air Force also reportedly maintains unmanned ISR aircraft at Sigonella.²⁰¹

According to DMDC, approximately 12,375 active-duty servicemembers were permanently assigned to Italy as of March 2024.²⁰²

Kosovo

Since 1999, the United States has maintained military forces in Kosovo to support NATO's Kosovo Force (KFOR), a peacekeeping effort. The U.S. Army's Area Support Group – Balkans maintains a headquarters for U.S. military activity in the Balkans at Camp Bondsteel in Kosovo.²⁰³

According to DMDC, approximately 14 active-duty servicemembers were permanently assigned to Kosovo as of March 2024.²⁰⁴ However, according to a December 2023 letter submitted by the Biden Administration to congressional leaders regarding the War Powers Report "approximately 578 United States military personnel are [present in Kosovo] among KFOR's approximately 4,487 personnel."²⁰⁵

Latvia

DOD regularly conducts exercises in and rotational deployments to Latvia. A U.S. Marine Expeditionary Unit made a port visit to Latvia in September 2023.²⁰⁶ Between 2015 and 2018, DOD received $13 million in military construction appropriations funds for infrastructure improvements at Lielvarde Air Base.²⁰⁷

According to DMDC, approximately 19 active-duty servicemembers were permanently assigned to Latvia as of March 2024.²⁰⁸ However, media reports suggest the United States reportedly deployed about 600 servicemembers deployed to Latvia in 2022, including some rotational forces at Lielvarde Air Base.²⁰⁹

Lithuania

DOD regularly conducts exercises in and rotational deployments to Lithuania. In December 2022, the U.S. Embassy in Lithuania announced the intent to maintain a "persistent rotational presence" of a U.S. Army armored battalion and field artillery battery in Lithuania. The Lithuanian government built Camp Herkus at the Pabrade Training Area to support an increased U.S. military presence in the country, and has reportedly requested that the United States establish a permanent base in the country.²¹⁰ U.S. Army soldiers trained at Camp Herkus in April 2022;²¹¹ and U.S. soldiers also conducted training exercises with Lithuanian military units at the Pabrade Training Area in November 2023.²¹²

According to DMDC, approximately 19 active-duty servicemembers were permanently assigned to Lithuania as of March 2024.²¹³ However, in March 2023, the Lithuanian government reported that 966 U.S. servicemembers were present in the country.²¹⁴

Norway

The U.S. Air Force maintains the 426^th Air Base Squadron at the Jåttå Military Compound in Stavanger, Norway, which serves as the U.S. National Support Element for the NATO Joint Warfare Centre.²¹⁵

In April 2021, the U.S. and Norway signed a security agreement that provides for the U.S. military "to access specific Norwegian facilities and conduct activities for our mutual defense."²¹⁶ The "focal points for increased cooperation with Norway" include Evenes Air Station, Ramsund Naval Station, Rygge Air Station, and Sola Air Station.²¹⁷

The Marine Corps has conducted training exercises in Norway, and maintains a stockpile of prepositioned material in the country. ²¹⁸

According to DMDC, approximately 1,438 active-duty servicemembers were permanently assigned to Norway as of March 2024.²¹⁹

Poland

In March 2023, the Army began to permanently assign soldiers to the Victory Corps, or V Corps, forward headquarters at Camp Kosciuszko, in Poznan, Poland.²²⁰ U.S. Army Garrison Poland supports three forward operating sites (FOS) in Poland: Camp Kosciuszko in Poznan, FOS Powidz, and FOS Zagan.²²¹ Other locations in Poland that periodically support U.S. rotational forces include Skwierzyna, Świętoszów, Drawsko Pomorskie, Bolesławiec and Toruń.²²² More than 100 infrastructure projects to support the U.S. military in Poland are reportedly in the works, ranging from dining facilities and barracks to training ranges.²²³ Most U.S. troops in Poland are reportedly there on nine-month rotations.²²⁴

U.S. military capabilities in Poland reportedly include an armor brigade; Patriot surface-to-air missile defense systems; F-22 Raptor combat aircraft; and unmanned ISR aircraft.²²⁵

The U.S. military is also installing an Aegis Ashore Ballistic Missile Defense (AABMD) system at Naval Support Facility Redzikowo, a former military and civilian airfield 225 miles northwest of Warsaw; NSF Redzikowo – which DOD has referred to as "the Navy's newest base" – is operated in conjunction with the Polish Force Protection Battalion.²²⁶

U.S. Air Force F-16 units have deployed to Lask Air Base near Lodz, Poland, and F-22s have deployed to Powidz Air Base in Poland to support NATO Allied Air Command's Air Shielding mission along NATO's eastern flank.²²⁷ The U.S. Air Force also reportedly operates air-refueling aircraft from Powidz Air Base.²²⁸

According to DMDC, as of March 2024, 299 active-duty U.S. military servicemembers were permanently assigned to Poland.²²⁹ However, in October 2022, the U.S. State Department reported that the U.S. maintains a rotational force of about 10,000 servicemembers in Poland, which includes an armored brigade combat team, funded through the European Deterrence Initiative.²³⁰

Portugal

The U.S. Air Force operates Lajes Field in the Azores Islands, a Portuguese territory located about 1,000 miles west of continental Europe. Lajes Field is the home of the 65^th Air Base Wing, which supports trans-Atlantic military operations.²³¹

According to DMDC, as of March 2024, 247 active-duty U.S. military servicemembers were permanently assigned to Portugal.²³²

Romania

Romania hosts a rotational presence of U.S. forces at several military facilities. In April 2023, the EUCOM commander testified that the rotational presence in Romania at that time included a U.S. Division headquarters, a U.S. brigade combat team, and a U.S. helicopter battalion.²³³

U.S. bomber aircraft have conducted refueling exercises at Mihail Kogălniceanu Air Base, Romania.²³⁴ F-22 units have conducted training at Camp Turzii, Romania, to support NATO Allied Air Command's Air Shielding mission along the eastern flank.²³⁵

The U.S. Navy operates an Aegis Ashore Missile Defense System (AAMDS) site in Romania at Naval Support Facility (NSF) Deveselu.²³⁶

DOD reports Mihail Kogălniceanu Air Base, Turzii, and NSF Deveselu as DOD facilities on the FY2023 Base Structure Report and the three facilities have received MILCON funding.²³⁷

According to DMDC, as of March 2024, 139 active-duty U.S. military servicemembers were permanently assigned to Romania.²³⁸ However, according to the U.S. Department of State, in February 2023 approximately 3,000 DOD personnel were present in Romania.²³⁹

Spain

Spain hosts U.S. Navy and Air Force bases.

Naval Station Rota, located near the Strait of Gibraltar, provides cargo, fuel, and logistics support to Navy ships and military units transiting the region.²⁴⁰ The U.S. Navy homeports four Arleigh Burke-class destroyers in Rota.²⁴¹ The destroyers are equipped with Aegis Baseline 9 Ballistic Missile Defense systems and are a component of EUCOM's regional missile defense strategies.²⁴² The U.S. and the government of Spain announced in May 2023 an agreement to expand the size of the Navy fleet authorized to homeport in Rota from four warships to six.²⁴³

Moron Air Base is about 75 miles northeast of Naval Station Rota. Moron hosts the 496^th Air Base Squadron and provides logistical support for moving military equipment and personnel into EUCOM and other regional combatant commands; it has large runways and a refueling systems.²⁴⁴

According to DMDC, as of March 2024, 3,292 active-duty U.S. military servicemembers were permanently assigned to Spain.²⁴⁵

Türkiye

Türkiye hosts U.S. Air Force and Army bases.

The Air Force operates aviation facilities at Incirlik Air Base and a rotational presence of aerial refueling capabilities.²⁴⁶ Several open-source media outlets have speculated about whether U.S. tactical nuclear weapons are based at Incirlik Air Base.²⁴⁷ While Incirlik is located in the EUCOM AOR, the facilities and personnel there frequently support operations in CENTCOM.²⁴⁸

Other key U.S./NATO sites in Türkiye include an early warning missile defense radar in Kürecik in eastern Türkiye.²⁴⁹ Izmir Air Station hosts a headquarters for NATO Allied Land Command.²⁵⁰

Diplomatic tensions between the U.S. and Türkiye have reportedly prompted the Turkish government in some situations to consider imposing limits on U.S. military access to Incirlik.²⁵¹

According to DMDC, as of March 2024, 1,690 active-duty U.S. military servicemembers were permanently assigned to Türkiye.²⁵²

United Kingdom

Royal Air Force Lakenheath is the headquarters for the U.S. Air Force's 48^th Fighter Wing, which is the U.S. Air Force's only fourth- and fifth-generation fighter wing in Europe; it includes F-35A Lightening II Joint Strike Fighters and F-15E Strike Eagles.²⁵³ In addition to combat aircraft, U.S. military capabilities in the U.K. reportedly include tanker refueling aircraft (KC-135R/T Stratotankers), ISR aircraft, and V-22 Osprey tilt-rotor aircraft.²⁵⁴ U.S. Strategic Command also reportedly maintains AN/FPS-132 Upgraded Early Warning Radar in the U.K.²⁵⁵

RAF Mildenhall hosts the 100^th Air Refueling Wing, which operates KC-135 Stratotanker aircraft.²⁵⁶ RAF Alconbury is a U.S. facility that hosts U.S. rotational forces.²⁵⁷ RAF Molesworth is home to the EUCOM Joint Intelligence Operations Center Europe Analytic Center.²⁵⁸

Bases in the U.K. also host rotational deployments of U.S. Air Force bomber aircraft from U.S.-based units.²⁵⁹

According to DMDC, as of March 2024, 10,058 active-duty U.S. military servicemembers were permanently assigned to the United Kingdom.²⁶⁰

Middle East

U.S. overseas basing in the Middle East is established and governed by bilateral executive agreements between the United States and regional governments—except in the case of Syria, where U.S. forces are present despite the opposition of Syria's government. Unlike in the Indo-Pacific or Europe, many U.S. servicemembers present in the Middle East appear to be on temporary or rotational assignments, and are thus not accounted for by DMDC's figures. To reflect this, throughout this section CRS has supplemented DMDC-provided figures—which only include permanently assigned servicemembers—with reporting or estimates from other sources, as appropriate. Some DOD documents and statements relating to this region refer to U.S. forces being deployed to and operating from "Southwest Asia," which may designate any number of locales (the usage of this term may reflect both operational security concerns and host-nation political sensitivities).

Bahrain

Bahrain hosts the U.S. Navy's Fifth Fleet and U.S. Naval Forces Central Command (NAVCENT) headquarters at an installation known as Naval Support Activity (NSA) Bahrain.²⁶¹ The U.S. Navy's base in Bahrain is one of the most enduring U.S. military sites in the region; the Navy's use of the facility dates back to 1948, when the base was operated by Britain's Royal Navy.²⁶²

The deep-water port in Bahrain is one of the few facilities in the Persian Gulf that accommodates U.S. aircraft carriers and amphibious assault ships.²⁶³ Navy ships homeported in Bahrain include four mine countermeasures ships (MCMs), one Expeditionary Support Base (ESB) ship, and two logistical support ships operated by the Military Sealift Command (MSC).²⁶⁴ DOD capabilities in Bahrain reportedly include P-8 Poseidon (an American maritime patrol and reconnaissance aircraft), EP-3E Aries II reconnaissance aircraft, and Patriot missile defense systems.²⁶⁵

The U.S. Coast Guard, which is overseen by the U.S. Department of Homeland Security, also maintains a squadron of ships in Bahrain, which consists of six fast response cutters, a cutter relief crew, and a 150-member mission support detachment.²⁶⁶

According to DMDC, as of March 2024, 3,479 active-duty U.S. military servicemembers were permanently assigned to Bahrain.²⁶⁷ However, DOD has also reported a total presence of 9,000 servicemembers and DOD civilians.²⁶⁸ It is likely that the number of DOD personnel fluctuates with the arrival and departure of U.S. ships.

Egypt

The U.S. military maintains a presence in Egypt as part of its support to the Multinational Force and Observers (MFO), an international peacekeeping force intended to "supervise the implementation of the security provisions of the Egyptian-Israeli Treaty of Peace and employ best efforts to prevent any violation of its terms."²⁶⁹

DOD also periodically participates in joint training and exercises with the Egyptian military, including at Cairo West Air Base.²⁷⁰

According to DMDC, as of March 2024, 176 active-duty U.S. military servicemembers were permanently assigned to Egypt.²⁷¹ However, according to a December 2023 letter submitted by the Biden Administration to congressional leaders regarding the War Powers Report, 416 military DOD personnel were present in Egypt as part of the U.S. commitment to the MFO."²⁷²

Iraq

U.S. servicemembers are based at a number of locations inside Iraq, including Al Asad Air Base and Erbil Air Base. ²⁷³ According to the White House, the purpose of the U.S. presence in Iraq is to "advise, assist, and enable select elements of the Iraqi security forces … [and] provide limited support to the North Atlantic Treaty Organization mission in Iraq."²⁷⁴ On a bilateral basis, the U.S. military presence in Iraq is governed by an exchange of diplomatic notes that reference the security provisions of the 2008 bilateral Strategic Framework Agreement.²⁷⁵ To date, this arrangement has not required the approval of a separate security agreement by Iraq's Council of Representatives. According to former Special Presidential Envoy for the Global Coalition to Counter ISIL Brett McGurk, the 2014 U.S.-Iraq diplomatic notes, which are not public, contain a one-year cancelation clause.²⁷⁶

U.S. and coalition training efforts for various Iraqi security forces have been implemented at different locations, including in the Kurdistan region, with U.S. training activities carried out pursuant to the authorities granted by Congress for the Iraq Train and Equip Program and the Office of Security Cooperation at the U.S. Embassy in Baghdad (OSC-I).²⁷⁷ OSC-I helps administer training and support programs funded through Foreign Military Sales and Foreign Military Financing assistance.²⁷⁸ Congress has authorized the continuation of train and equip program activities through December 2024 and appropriated funding for related programs that remains available through FY2024.

U.S. military capabilities in Iraq reportedly include AH-64E Apache helicopters, MH-47G Chinook helicopters, MH-60M Black Hawk helicopters, and unmanned surveillance aircraft.²⁷⁹

Since October 2023, U.S. bases in Iraq have been subject to numerous attacks by non-state actors in the region, and DOD has conducted strikes against targets in Iraq. For more information, see CRS Insight IN12309, Iraq: Attacks and U.S. Strikes Reopen Discussion of U.S. Military Presence, by Christopher M. Blanchard.

In December 2023, media reporting suggested that approximately 2,400 DOD personnel were present in Iraq.²⁸⁰

Israel

DOD participates in joint exercises with the Israeli military to foster interoperability.²⁸¹ DOD maintains an emergency stockpile of weapons and equipment in Israel.²⁸²

According to DMDC, as of March 2024, 115 active-duty U.S. military servicemembers were permanently assigned to Israel.²⁸³

Jordan

The Muwaffaq al Salti Air Base in Jordan reportedly hosts the headquarters of U.S. Air Forces Central's 332^nd Air Expeditionary Wing.²⁸⁴ In July 2023, DOD reportedly deployed F-35s to the base.²⁸⁵

In 2021, DOD transferred a stockpile of weaponry and supplies from a military base in Qatar to Jordan.²⁸⁶

In January 2024, U.S. Central Command reported that about 350 U.S. military personnel were deployed to a location known as Tower 22.²⁸⁷ Tower 22 is reportedly located near the borders of Iraq and Syria and close to the U.S. base at Al Tanf in Syria.²⁸⁸ A drone attack on Tower 22 killed three U.S. servicemembers in January 2024.²⁸⁹

According to a December 2023 letter submitted by the Biden Administration to congressional leaders regarding the War Powers Report, DOD had 3,188 military personnel in Jordan."²⁹⁰ The Biden Administration defines this mission as one "to support Defeat-[Islamic State] operations, to enhance Jordan's security, and to promote regional stability."²⁹¹

According to DMDC, as of March 2024, 120 active-duty U.S. military servicemembers were permanently assigned to Jordan.²⁹²

Kuwait

Camp Arifjan hosts the forward headquarters of U.S. Army Central (USARCENT), the Army component of CENTCOM.²⁹³ Task Force Spartan in Kuwait reportedly has included two brigades and four battalion task forces, which provide capabilities including helicopter aviation, logistics support, force protection, and information management.²⁹⁴ The Army maintains a stockpile of prepositioned materiel in Kuwait.²⁹⁵ The Army pre-positioned stocks (APS) in Kuwait are intended to outfit two combat Army brigades.²⁹⁶

At Ali Al-Salem Air Base, the U.S. Air Force's 386^th Air Expeditionary Wing is "the primary airlift hub and gateway for delivering combat power to joint and coalition forces in the U.S. Central Command [AOR]."²⁹⁷ U.S. Air Force capabilities in Kuwait include unmanned surveillance aircraft, including MQ-9 Reapers.²⁹⁸ DOD also has combat airlift capabilities in Kuwait.²⁹⁹

The largest U.S. air logistics facility in the region is in Kuwait, at the country's international airport, Kuwait International Airport.³⁰⁰

According to DMDC, as of March 2024, about 533 active-duty U.S. military servicemembers were permanently assigned to Kuwait.³⁰¹ However, in July 2021 the U.S. Department of State reported that approximately 13,500 U.S. servicemembers or personnel were based in Kuwait, primarily at Camp Arifjan and Ali Al-Salem Air Base.³⁰²

Qatar

Al Udeid Air Base hosts the headquarters of CENTCOM Forward, U.S. Air Forces Central Command (AFCENT) Forward, and U.S. Special Operations Command Central (SOCCENT) Forward, as well as CENTCOM's Combined Air Operations Center, the Combined Joint Interagency Task Force – Syria, and the U.S. Air Force's 379^th Air Expeditionary Wing, one of the largest expeditionary wings in the world.³⁰³ Since 2003, Qatar has contributed more than $8 billion in developing Al Udeid Air Base for use by the U.S. military.³⁰⁴ According to media reports, DOD recently reached a defense cooperation agreement with Qatar that includes terms extending U.S. use of Al Udeid by another ten years.³⁰⁵

DOD capabilities in Qatar reportedly include surveillance aircraft, tanker refueling (KC-135 Stratotankers), combat airlift (C-17A Globemasters, CH-130H Hercules), Patriot missile defense systems, and AN/TPY-2 X-band radar to support missile defense systems.³⁰⁶ The base hosts a rotational presence of combat aircraft.³⁰⁷

DOD also operates Camp As Sayliyah in Qatar, a former Army base that has been used as a U.S. government processing center for Afghans seeking resettlement.³⁰⁸

According to DMDC, as of March 2024, about 303 active-duty U.S. military servicemembers were permanently assigned to Qatar.³⁰⁹ However, media reports suggest there may be as many as 8,000 to 10,000 U.S. personnel operating in Qatar at any given time.³¹⁰

Saudi Arabia

In June 2024, the White House stated that approximately 2,321 U.S. military personnel were in Saudi Arabia.³¹¹ Most of these personnel appear to be stationed at Saudi Arabia's Prince Sultan Air Base (PSAB), which hosts the 378^th Air Expeditionary Wing, a U.S. Air Force unit that—according to U.S. Air Forces Central (AFCENT) as of October 2023—"supports approximately 2,200 airmen and soldiers assigned to PSAB, as well as the U.S. Army's Patriot missile defense capability and Terminal High Altitude Area Defense (THAAD) capability in the region."³¹² Air Force capabilities at PSAB include tanker refueling aircraft.³¹³ PSAB hosts rotational deployments of combat aircraft.³¹⁴

Syria

In June 2024, the White House stated that "a small presence of United States Armed Forces remains in strategically significant locations in Syria to conduct operations, in partnership with local, vetted ground forces, to address continuing terrorist threats emanating from Syria."³¹⁵ The U.S. military presence in Syria reportedly includes the base at Al Tanf and various facilities in northeastern Syria.³¹⁶ CENTCOM and DOD officials have also indicated a presence of U.S. forces at the Rumalyn Landing Zone, Mission Support Site Conoco, Mission Support Site Euphrates, Mission Support Site Green Village, and at Patrol Base Shaddadi, all in northeast Syria.³¹⁷

U.S. forces in Syria conduct counterterror missions against the Islamic State group and Al Qaeda-affiliated militants, and are equipped to defend themselves against Iran-backed militias that have attacked U.S. facilities.³¹⁸ They also advise and assist the Syrian Democratic Forces, on missions that include securing detention facilities holding Islamic State personnel.³¹⁹

The commander of U.S. Central Command said in March 2023 that there were approximately 900 servicemembers deployed to Syria, according to CENTCOM.³²⁰

United Arab Emirates

Al Dhafra Air Base hosts the Air Force's 380^th Air Expeditionary Wing, which includes surveillance aircraft such as MQ-9 Reapers.³²¹ Air Force capabilities in the UAE also reportedly include airborne early warning and control (AEW&C) aircraft; ISR aircraft; and tanker refueling aircraft.³²² Al Dhafra hosts rotations of combat aircraft units; in 2022, the Air Force deployed F-22 Raptors to the UAE.³²³ In April 2023, the Air Force deployed A-10 Thunderbolts to the UAE.³²⁴

Al Dhafra hosts the Gulf Air Warfare Center, which provides regionally focused air and missile defense training for around 2,000 participants from 10 nations every year.³²⁵ The UAE-owned Port of Jebel Ali and other UAE ports provide logistical support for the U.S. Navy and collectively host more Navy ships than any other port outside the United States.³²⁶

In early 2022, Al Dhafra Air Base was targeted by missile attacks from Yemen.³²⁷

U.S. officials have raised concerns about UAE ties to China and Russia.³²⁸

In February 2024, UAE reportedly placed restrictions on DOD's use of military bases located in UAE for launching retaliatory airstrikes on Iranian proxies.³²⁹

According to DMDC, as of March 2024, about 177 active-duty U.S. military servicemembers were permanently assigned to U.A.E.³³⁰ As of July 2021, the U.S. Department of State reported that about 3,500 servicemembers were based in U.A.E.³³¹

Yemen

In December 2023, the Biden Administration reported to Congress that "a small number" of U.S. military personnel "are deployed to Yemen to conduct operations against al-Qa'ida in the Arabian Peninsula and ISIS."³³² Information about the location of those servicemembers is not publicly available.

Africa

U.S. overseas basing in Africa is established and governed by bilateral executive agreements (e.g., DCAs/EDCAs, MOUs). Most of the U.S. servicemembers permanently assigned to this region are stationed at persistent bases in Djibouti. As in the Middle East, most U.S. servicemembers present in Africa appear to be on temporary or rotational assignments, and are thus not accounted for by DMDC's figures. To reflect this, throughout this section CRS has supplemented DMDC-provided figures (which only include permanently assigned servicemembers) with reporting or estimates from other sources, as appropriate.

Djibouti

Djibouti hosts Camp Lemonnier and Chabelley Airfield. Camp Lemonnier was first occupied by U.S. forces in 2002 and serves as the headquarters for Combined Joint Task Force – Horn of Africa, which conducts regional operations to "enhance partner nation capacity, promote regional stability, dissuade conflict, and protect U.S. and coalition interests."³³³ The base is located near the Bab al-Mandab Strait and supports operations in the Red Sea and beyond.³³⁴ In addition, since 2013 Djibouti has hosted Chabelley Airfield, which the Air Force describes as its "largest remotely piloted aircraft base in Africa."³³⁵

According to DMDC, approximately 406 active-duty servicemembers were permanently assigned to Djibouti as of March 2024.³³⁶ However, according to the Navy, Camp Lemonnier supports "approximately 4,000 U.S., joint, and allied forces military and civilian personnel."³³⁷

Gabon

Gabon hosts a cooperative security location in the capital of Libreville.³³⁸ According to the U.S. State Department, access to this base contributes to "enabling the projection of forces in central and southern Africa".³³⁹

According to DMDC, approximately 12 active-duty servicemembers were permanently assigned to Gabon as of March 2024.³⁴⁰

Kenya

Kenya hosts U.S. forces at Manda Bay, a cooperative security location along the country's eastern coast.³⁴¹ According to DOD, Manda Bay is used to "provide training to African partners, respond to crises and protect U.S. interests," and base operations are managed by the U.S. Air Force.³⁴² In 2020, Manda Bay was attacked by al-Shabaab militants, leading to the deaths of one U.S. soldier and two U.S. contract personnel.³⁴³ DOD's Base Structure Report and AFRICOM also identify Mombasa as the site of a cooperative security location.³⁴⁴

According to DMDC, approximately 65 active-duty servicemembers were permanently assigned to Kenya as of March 2024.³⁴⁵

Niger

Prior to April 2024, Niger hosted U.S. forces at multiple locations in the country, including two bases known as Air Base 101 (located near the capital, Niamey) and Air Base 201 (located in the city of Agadez). According to DOD, these sites supported counterterrorism operations and security assistance activities.³⁴⁶ However, following a 2023 coup d'état, the U.S. Department of State announced the suspension of economic and military aid to Niger, and in March 2024 the Nigerien government announced the termination of its SOFA with the United States.³⁴⁷ In May 2024, the Biden Administration announced that U.S. forces would withdraw from the country by September 15, 2024.³⁴⁸

According to DMDC, approximately 72 active-duty servicemembers were permanently assigned to Niger as of March 2024.³⁴⁹ As of June 2024, the White House stated that "approximately 700 United States military personnel are currently deployed to Niger … however, the Department of Defense is in the process of withdrawing United States military personnel from Niger, and the withdrawal will be completed over the next several months."³⁵⁰

British Overseas Territory of Saint Helena, Ascension Island, and Tristan da Cunha (Ascension Island)

Ascension Island, part of the British Overseas Territory of Saint Helena, Ascension Island, and Tristan da Cunha, hosts U.S. Air Force and Space Force facilities and personnel at Ascension Island Auxiliary Airfield. AFRICOM has stated that this base is one of two "enduring Forward Operating Sites in Africa" (the other being Camp Lemonnier).³⁵¹ According to the Space Force, in 2023 DOD completed a "$352.6 million, full-depth rebuild of the remote runway" at the base.³⁵² DOD has stated that its presence at Ascension Island supports air logistics operations and space launch tracking.³⁵³

According to DMDC, approximately three active-duty servicemembers were permanently assigned to the "British Atlantic Ocean Territory" (which appears to be identical with the British Overseas Territory of Saint Helena, Ascension Island, and Tristan da Cunha) as of March 2024.³⁵⁴

Senegal

Senegal provides U.S. forces with access "for exclusive use" to Captain Andalla Cissé Air Base (located in the capital, Dakar), as well as access "for joint use" to Thiès Air Base (located in the town of Thiès) and Admiral Faye Gassama Naval Base (located in Dakar).³⁵⁵ According to the U.S. State Department, access to these facilities supports U.S. operations in the region, which may include security assistance activities as well as humanitarian response, evacuation support, or logistical activities.³⁵⁶

According to DMDC, approximately 22 active-duty servicemembers were permanently assigned to Senegal as of March 2024.³⁵⁷

Somalia

According to DOD, Somalia hosts "a small, persistent U.S. military presence" that supports the "training, advising and equipping [of] partner forces to five them the tools they need to disrupt, degrade and monitor al-Shabab." The locations at which these forces are deployed are unclear from publicly available sources, but Baledogle and Kismayo have been identified by U.S. government sources as locations hosting indeterminate numbers of U.S. troops.³⁵⁸ In June 2024, the White House stated that "United States military personnel conduct periodic engagements in Somalia to train, advise, and assist regional forces, including Somali and African Union Transition Mission in Somalia forces, in connection with counterterrorism operations."³⁵⁹

According to DMDC, approximately 60 active-duty servicemembers were permanently assigned to Somalia as of March 2024.³⁶⁰ However, media reports suggest the total number of U.S. servicemembers present in Somalia may be between 100 and 500.³⁶¹

Latin America and the Caribbean

U.S. overseas basing in Latin America and the Caribbean is established and governed by bilateral executive agreements (DCAs/EDCAs, MOUs, Strategic Framework Agreements, etc.)—except in the case of Cuba, where U.S. forces are present pursuant to diplomatic agreements that the current Cuban government does not consider legitimate.³⁶²

Aruba and Curaçao (Constituent Countries of the Netherlands)

Aruba hosts a cooperative security location at its Reina Beatrix International Airport, and Curaçao hosts a cooperative security location at its Hato International Airport.³⁶³ Both bases are managed by the Air Force and support counter-narcotics missions.³⁶⁴ Aruba and Curaçao are each constituent countries of the Kingdom of the Netherlands, meaning that the Dutch government handles their foreign and defense policies.³⁶⁵

According to DMDC, no active-duty servicemembers were permanently assigned to Aruba or Curaçao as of March 2024.³⁶⁶

The Bahamas

The United States maintains the Atlantic Undersea Test and Evaluation Center (AUTEC) in the Bahamas. AUTEC primarily supports U.S. Navy research, development, test, and evaluation activities, particularly those relating to submarine and anti-submarine warfare, and includes a number of underwater and "in-air" test facilities.³⁶⁷

According to DMDC, 63 active-duty servicemembers were permanently assigned to the Bahamas as of March 2024.³⁶⁸

Cuba

The United States maintains Naval Station Guantanamo Bay in Cuba. The base includes a facility that has been used to detain U.S. military prisoners, including some captured during the Global War on Terror; according to the Navy, it also "support[s] unified, inter-agency joint operations, and training."³⁶⁹ Compared to other overseas basing relationships, that between the United States and Cuba is unique. The U.S. government holds that DOD's presence at Guantanamo Bay is authorized by diplomatic agreements (two 1903 executive agreements and one 1934 treaty) concluded prior to the 1958 Cuban Revolution, while the current Cuban government views these as illegitimate and claims that the United States "illegally occupies" the base.³⁷⁰

According to DMDC, 616 active-duty servicemembers were permanently assigned to Cuba as of March 2024.³⁷¹

El Salvador

El Salvador hosts Cooperative Security Location Comalapa, a Navy base located in Comalapa, El Salvador. According to SOUTHCOM, it supports efforts to combat transnational organized crime, particularly the detection and interdiction of illegal narcotics.³⁷²

According to DMDC, 54 active-duty servicemembers were permanently assigned to El Salvador as of March 2024.³⁷³

Honduras

Honduras hosts Soto Cano Air Base, an Army base located in near the town of Comayagua. According to SOUTHCOM, it is the only forward operating site in Central and South America.³⁷⁴ Soto Cano supports Joint Task Force-Bravo, a SOUTHCOM task force intended to "counter transnational organized crime, [provide] humanitarian assistance/disaster relief efforts and the development of partner capacities, [and promote regional cooperation and security in Central America, South America and the Caribbean."³⁷⁵ The 1^st Battalion, 228^th Aviation Regiment operates from Soto Cano with assets including UH-60L Black Hawk, CH-47F Chinook, and MEDEVAC HH-60L helicopters.³⁷⁶

According to DMDC, 365 active-duty U.S. servicemembers were permanently assigned to Honduras as of March 2024.³⁷⁷

Appendix B. Selected U.S. Overseas Bases

Appendix C. DOD Definitions and Methodological Issues

DOD divides its overseas bases into two broad categories: enduring locations, which support U.S. military activities on an ongoing basis, and contingency locations, which provide temporary support for combat missions and other contingency operations.³⁷⁸ Enduring locations fall into one of three categories, depending on the degree of U.S. presence:

• Main operating base. Defined by DOD as "a facility outside the United States and its territories with permanently stationed operating forces and robust infrastructure."³⁷⁹
• Forward operating site. Defined by DOD as "a scalable location outside the United States and its territories intended for rotational use by operating forces."³⁸⁰
• Cooperative security location. Defined by DOD as "a facility located outside the United States and its territories with little or no permanent United States presence that is maintained by periodic Service, contractor, or host nation support."³⁸¹

Similarly, DOD sorts its contingency locations into categories based on the timeframe of their intended use: (1) initial locations (immediate need); (2) temporary locations (1-24 months); or (3) semipermanent locations (24-60 months).³⁸²

Despite these official definitions, in practice there exists some ambiguity in the ways DOD and other U.S. government (USG) organizations consider overseas basing. The distinctions between DOD's three categories of enduring locations are sometimes unclear. For instance, although the department's definition of forward operating sites states that they support "rotational use," senior officials have also indicated that some individual forward operating sites support a "permanent" presence of U.S. forces.³⁸³ Additionally, DOD's official taxonomy does not appear to be consistently used across the department. For instance, although DOD defines a cooperative security location as a type of enduring location located outside U.S. territory (and thus, an overseas base), some DOD organizations have published material suggesting that cooperative security locations should not be considered overseas bases.³⁸⁴ Officially defined terms may also be used inconsistently in colloquial or casual descriptions by U.S. or foreign officials and other stakeholders.

DOD real property accounting methods may further compound uncertainty. To meet its statutory reporting requirements, every fiscal year (FY) the Department publishes a "Base Structure Report" (BSR).³⁸⁵ Despite its title, this document does not report real property by base, but rather by site.³⁸⁶ According to the "Summary" section of the FY2023 BSR (the most recent publicly available report), DOD maintains 511 overseas sites.³⁸⁷ However, this figure does not appear to be a reliable proxy for the number of overseas bases as defined by this report, for two reasons. First, multiple sites are sometimes reported for a location that DOD's stated definitions suggest should constitute a single base.³⁸⁸ Second, there are some active military sites that meet the criteria for overseas bases, but do not appear on the BSR.³⁸⁹

DOD also maintains a classified "Enduring Location Master List (ELML") which it uses to "identify, validate, and document locations that represent an enduring, strategic U.S. security interest for the foreseeable future."³⁹⁰ As this document is classified, its contents were not used in the preparation of this report.

Other shifts in DOD's approach to overseas basing may also complicate the question of what constitutes an overseas base. Compared to basing during the Cold War, DOD's current posture relies to a larger extent on defense infrastructure owned and operated by allied and partner nations. Some of these sites are not associated with any locations designated in official DOD or USG documentation as overseas bases, yet routinely host deployed U.S. forces and/or receive upgrades to real property funded by the services' military construction (MILCON) appropriations.³⁹¹

A final factor for consideration is the political significance—both domestically and internationally—of characterizing locations as overseas bases. The executive branch generally, and DOD specifically, may choose not to apply the term to sites that otherwise meet their criteria in order to minimize public or congressional scrutiny of politically, diplomatically, or militarily sensitive executive branch actions.³⁹² They may also avoid the term out of deference to host-nation sensitivities, or to minimize risks from regional state or non-state actors that might seek to target U.S. forces.³⁹³