Introduction

Encompassing the seas, islands, and littoral areas of the Pacific and Indian Oceans between the western coast of North America and India (see Figure 1), the Indo-Pacific region hosts more than 375,000 U.S. military personnel using at least 66 distinct defense sites.¹ The 2022 National Security Strategy describes 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."² Secretary of Defense Lloyd Austin has described Indo-Pacific defense infrastructure as "provid[ing] us with the ability to position our troops forward in theater, so that we can deter much further forward."³

Given the role of defense infrastructure in undergirding U.S. military presence and power projection in the region, Congress has devoted considerable attention to Indo-Pacific defense infrastructure issues, and may choose to do so in the future. This report

• defines the fundamental elements of infrastructure policy and basing posture;
• describes the historical development of Indo-Pacific defense infrastructure;
• characterizes the strategic and operational roles of Indo-Pacific defense sites;
• describes the current U.S. basing posture in Alaska, Washington, California, Hawaii, Wake Island, Guam, the Northern Mariana Islands, the Marshall Islands, Japan, the Republic of Korea, the Philippines, Singapore, Australia, and the British Indian Ocean Territory (Diego Garcia); and
• analyzes selected issues for congressional consideration.⁴

Figure 1. The Indo-Pacific Region

Source: "U.S. INDOPACOM Area of Responsibility," https://www.pacom.mil/About-USINDOPACOM/USPACOM-Area-of-Responsibility/. Notes: The continental United States, Canada, Mexico, and surrounding waters to a distance of 500 nautical miles from shore fall within the U.S. Northern Command AOR. See https://www.northcom.mil/About.

Background

Defining Defense Infrastructure

Defense infrastructure consists of the buildings, permanent facilities, fixed systems, real property, and related assets owned, operated, or used by a nation's government for military purposes. For DOD, the basic 'unit' of infrastructure is the installation, defined statutorily 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."⁵ An installation or group of installations may serve as a base, which DOD defines as "a locality from which operations are projected or supported."⁶ DOD classifies its overseas bases into two categories: enduring locations, which support ongoing activities and interests on a permanent basis; and contingency locations, which provide temporary support for contingency operations.⁷

Each military department (MILDEP) manages its infrastructure through its own organizational structures, policies, and programs, while the Under Secretary of Defense for Acquisition and Sustainment sets policy and exercises oversight of infrastructure-related matters across DOD.⁸ The construction of new facilities is funded through Military Construction (MILCON) appropriations, while other infrastructure-related functions such as facilities sustainment, restoration, and modernization (FSRM) and base operations are funded through Operation and Maintenance (O&M) appropriations.

Within the Indo-Pacific region, this report identifies and describes 66 military bases. Of these, 26 are located to the east of the International Date Line (IDL), and 40 are located to the west of the IDL (see Figure 2). The majority of sites are within the U.S. Indo-Pacific Command (INDOPACOM) Area of Responsibility (AOR); also included are select locations in Alaska, Washington, and California that fall within the U.S. Northern Command (NORTHCOM) AOR but are located in the Indo-Pacific region as defined above and provide substantial support for regionally focused operations.

Defense infrastructure in the Indo-Pacific performs or supports an array of military functions, including

• Basing of personnel and weapons systems. The most fundamental function of military installations is to provide space for servicemembers, weapons systems, and the resources necessary for their operation (e.g., food, fuel, munitions). Installations serve as work sites during both peacetime and wartime, enabling activities ranging from routine office work to launching combat missions. Larger installations often include housing for defense personnel and dependents, as well as morale, welfare and recreation (MWR) facilities.
• Domain awareness and area defense. Beyond their role in hosting combat forces, fixed sites and facilities play a key role in detecting and countering threats to U.S. and allied forces and territory. Elements of Indo-Pacific defense infrastructure performing or supporting this mission include radar sites intended to detect incoming missiles or aircraft (e.g., Shariki Communications Site, Japan) and ground-based interceptor sites intended to neutralize incoming missiles (e.g., Ft. Greely, AK).⁹
• Maintenance and repair. The complexity of major weapons systems often requires specialized facilities and equipment to conduct maintenance, repair, and overhaul activities. These may include vehicle maintenance facilities, aircraft maintenance hangars, and naval shipyards. Examples of Indo-Pacific facilities performing maintenance and repair functions include the U.S. Naval Ship Repair Facility and Japan Regional Maintenance Center (part of Fleet Activities Yokosuka and Fleet Activities Sasebo, Japan).¹⁰
• Training and exercises. U.S. and allied forces rely on regional training and exercise areas to maintain and enhance readiness, test operational plans and concepts, and demonstrate and improve interoperability. Examples of Indo-Pacific sites used for training and exercises include the Jungle Warfare Training Center at Camp Gonsalves in Okinawa, Japan and the Black Rapids Training Site in Black Rapids, AK.¹¹
• Storage, prepositioning, and distribution of equipment and supplies. To ensure logistical preparedness and enable rapid contingency responses, the U.S. military stores equipment and supplies at locations across the Indo-Pacific. These stocks are maintained in a variety of ways, including aboard regionally based maritime prepositioning ships (such as those homeported in Diego Garcia) and at facilities such as the Defense Logistics Agency's Distribution Yokosuka in Japan.¹²
• Research, development, test, and evaluation (RDT&E). DOD uses a number of Indo-Pacific sites to develop and test new technologies and weapon systems, especially those requiring large amounts of air or ocean space. Examples of major RDT&E sites in the region include the Pacific Missile Range Facility, Barking Sands in Hawaii and the Ronald Reagan Ballistic Missile Defense Test Site in the Marshall Islands.¹³

Strategic and Operational Role

Infrastructure and National Strategy

A review of planning and policy documents issued by the White House and the Department of Defense since 2020 illustrates the importance of Indo-Pacific defense infrastructure to contemporary U.S. strategy. The 2021 Global Posture Review identified a need to "seek greater regional access for military partnership activities" and "enhance infrastructure in Australia and the Pacific Islands" to accomplish DOD's goals of "contribut[ing] to regional stability and deter[ring] potential Chinese military aggression and threats from North Korea."¹⁴ The 2022 Indo-Pacific Strategy articulates four security-related U.S. objectives in the region: advancing a free and open region, building connections to and among regional partners, bolstering regional security, and building resilience to transnational threats.¹⁵ Both the 2022 National Security Strategy (NSS) and National Defense Strategy (NDS) characterize PRC attempts to reshape the Indo-Pacific and the broader international order as the most acute military threat to U.S. interests, and DOD officials have stated in congressional testimony that "a Taiwan contingency is the pacing scenario" for U.S. planners.¹⁶ The NSS identifies a "strong and consistent defense presence" as a key contributor to regional peace and stability, while the NDS states that DOD will "reinforce and build out a resilient security architecture in the Indo-Pacific region."¹⁷ The NDS also identifies the following four "top-level defense priorities."

• Defending the homeland, paced to the growing multi-domain threat posed by the PRC.
• Deterring strategic attacks against the United States, allies, and partners.
• Deterring aggression, while being prepared to prevail in conflict when necessary.
• Building a resilient Joint Force and defense ecosystem.¹⁸

Although only the Global Posture Review explicitly mentions defense infrastructure, the Indo-Pacific Strategy, NSS, and NDS all emphasize the strategic centrality of a sustained, significant forward U.S. military presence; such a presence would rely heavily on a network of regional defense sites. The six broad functions of Indo-Pacific infrastructure described above—basing of personnel and weapons systems, domain awareness and area defense, maintenance and repair, support for training and exercises, storage, prepositioning, and distribution of equipment and supplies, and support for RDT&E activities—are essential enablers of the regional presence and operation of the U.S. military. This is especially true for naval and air forces, which require extensive and specialized facilities for storage, operation, maintenance, and repair.

Indo-Pacific defense infrastructure also supports the four top-level defense priorities identified in the NDS. Sites in Japan, Alaska, California, and elsewhere host detection and defense capabilities intended to protect the U.S. homeland from both conventional and nuclear attack. To deter strategic attacks on the United States or its allies, DOD relies on Indo-Pacific sites to enable the "forward deployment of strategic bombers, dual-capable fighter aircraft, and nuclear weapons to region and globally… including ballistic missile submarine port visits and strategic bomber missions."¹⁹ A robust regional basing posture may also help deter aggression by signaling enduring U.S. commitment to the region. Alternatively, some analysts have suggested that a large U.S. military footprint may intensify the security dilemma and thus make aggressive state behavior more likely).²⁰ Finally, the scale and diversity of functions performed or supported by Indo-Pacific defense infrastructure contributes to the broader priority of "building a resilient Joint Force and broader defense ecosystem."²¹

Infrastructure in a Contested Environment

The operational role of defense infrastructure is susceptible to change should significant geopolitical shifts occur. Under current peacetime conditions, concentrating infrastructure near operational areas can yield a number of advantages. Clustering military facilities in a smaller number of sites is cheaper and creates organizational and logistical efficiencies, while locating bases near operational areas shortens transit and allows units to spend more time on station (this is particularly important for aircraft, given their range limitations).²²

However, in the event of a conflict between the United States and a regional power with significant air and missile capabilities, this same concentration and proximity would expose U.S. forces and facilities west of the International Date Line—especially those within the First and Second Island Chains—to a higher likelihood of successful adversary attack. Some analysts argue the most acute threat to U.S. infrastructure in the Indo-Pacific stems from the PRC's missile capabilities, which the DOD's 2022 Missile Defense Review characterizes in the following manner:

Over the past two decades, the PRC has dramatically advanced its development of conventional and nuclear-armed ballistic and hypersonic missile technologies and capabilities, through intense and focused investment, development, testing, and deployments… In many areas such as conventional ballistic and hypersonic missile technologies, the PRC continues to close the gap with the United States, and will likely continue to develop and expand its missile capabilities. Increasingly sophisticated and proliferated space-based Intelligence, Surveillance, and Reconnaissance (ISR) networks, and improved Command and Control (C2) systems, have greatly improved the precision and accuracy of missile systems the PRC would employ to deter and counter U.S. forward presence and operations, especially in the Western Pacific region.²³

Although North Korean air and missile strike capabilities are considerably less developed than those of the PRC, DOD assesses that "North Korea continues to improve, expand, and diversify its conventional and nuclear missile capabilities, posing an increasing risk to the U.S. homeland and U.S. forces in theater, as well as regional allies and partners."²⁴

To meet the demands of a contested environment, 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.²⁵ Although some aspects of these three concepts are globally applicable, they are particularly oriented around potential Indo-Pacific contingencies.

These distributed operational concepts represent a break from previous planning paradigms, and will make accordingly different use of defense infrastructure. The most radical change may come in the air domain. 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."²⁶ 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) between which aircraft can be shifted and from which sorties may be launched.²⁷

Although the infrastructure implications of the Army's MDO and the Navy's DMO are less sweeping, both entail 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).²⁸ 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."²⁹ Given the novel character of these operational concepts, their implementation may carry significant implications for regional basing posture, resourcing, and management.

Current U.S. Basing Posture

Within the Indo-Pacific region, the United States currently utilizes at least 66 significant defense sites spread across four U.S. states, three U.S. territories, eight countries, and one British overseas territory (see the map of U.S. defense sites provided in Figure 2 below; a more detailed description of each regional defense site is also provided in the Appendix A). These sites include

• installations that are owned and operated by DOD (this arrangement is the norm in U.S. states and territories);
• installations that are operated by DOD but located in host nations (this arrangement is the norm in South Korea, Japan, and the British Indian Ocean Territory); and
• installations that are used by DOD but owned and operated by host nations (this arrangement is the norm in the Philippines, Singapore, and Australia).

Some analysts and policymakers also divide regional defense sites between those located east of the International Date Line (i.e., bases in Alaska, Washington, California, and Hawaii) and those located west of the International Date Line.³⁰ This division is analytically useful because sites west of the International Date Line (IDL) may be within range of adversaries' conventional strike capabilities and would likely be used to directly support forward combat operations in a contingency, while those east of the IDL would likely be less susceptible to opponents' conventional strike capabilities.³¹ Moreover, because the majority of sites west of the IDL are located outside of the United States, their use entails diplomatic and management considerations (e.g., relations with host nation governments, the applicability of foreign legal regimes to land use) that do not exist for sites east of the IDL.

Figure 2. U.S. Defense Sites in the Indo-Pacific

Source: CRS graphic based on analysis of DOD information, including the "FY2022 Base Structure Report," installation and unit web pages, and related documentation. Notes: Naval Communications Station Harold E. Holt (located near Exmouth, Australia) is not depicted due to space constraints.

Geographic Overview

Most of the Indo-Pacific region falls within the U.S. INDOPACOM AOR. This COCOM accordingly exercises oversight and theater-level direction over the strategic and operational functions of theater infrastructure (installations located in Alaska, Washington, and California fall within the U.S. NORTHCOM AOR).

All of DOD's uniformed service branches operate installations in the region. The Army, Navy, Marine Corps, and Air Force operate installations in the INDOPACOM AOR.

Major Army installations are mainly concentrated in Alaska, Washington, Hawaii, South Korea, Japan, and the Republic of the Marshall Islands. These installations provide basing for ground units, missile detection and defense capabilities, and facilities for training, exercises, RDT&E activities, and logistical support.

Major Navy installations are concentrated in Washington, California, Hawaii, Guam, Japan, and Diego Garcia. These installations provide basing and maintenance and repair capabilities for ships and aircraft, as well as facilities for training, exercises, RDT&E activities, and logistical support. Major Marine Corps installations are concentrated in California, Hawaii, Guam, and Japan. These installations provide basing for ground units and aircraft as well as facilities for training, exercises, and logistical support.

Major Air Force installations are concentrated in Alaska, Washington, California, Hawaii, Guam, South Korea, and Japan. These installations provide aircraft basing and maintenance and repair capabilities, missile detection and defense capabilities, and facilities for logistical support. Space Force installations are located in Alaska and California. These installations provide space domain awareness, missile detection and defense, and space launch capabilities.

East of the International Date Line

This report identifies 26 bases east of the IDL that support Indo-Pacific defense functions (see Figure 3 below).

Figure 3. U.S. Defense Sites, East of the International Date Line

Source: CRS graphic based on analysis of DOD information, including the "FY2022 Base Structure Report," installation and unit web pages, and related documentation. Notes: Given space and scope constraints, this map, and the Appendix – Key Sites and Facilities, does not include several major installations located in California (e.g., Edwards AFB) because their functions are not directly or specifically oriented around support for operations in the Indo-Pacific theater.

Alaska

Alaska hosts Indo-Pacific-focused Army, Air Force, and Space Force installations, including Fort Wainwright, Joint Base Elmendorf-Richardson, Eielson Air Force Base, and Clear Space Force station. These sites are used to base Army ground units (including the headquarters of the 11^th Airborne Division and two of its combat brigades), Army aviation units (including two aviation battalions and Air Force aircraft (including fighter, command and control, and airlift squadrons). DOD also uses defense infrastructure in Alaska to detect and intercept missile threats to the continental United States and provide specialized training for cold weather and mountain environments.³² Several open source press reports have also highlighted the role smaller Alaskan airfields may play in a regional contingency.³³

Washington

Washington hosts Indo-Pacific-focused Army, Navy, and Air Force installations, including Joint Base Lewis-McChord, Naval Base Kitsap, and Fairchild Air Force Base. These sites are used to base Army units (including the 7^th Infantry Division), Navy vessels (including two aircraft carriers, three submarine squadrons, and seven destroyers), and Navy and Air Force aircraft (including Navy electronic attack, maritime patrol, and reconnaissance squadrons and Air Force airlift and refueling squadrons). DOD also uses defense infrastructure in Washington to maintain and repair naval vessels, store and maintain submarine-based nuclear weapons, store and distribute fuel, and train ground and air units.³⁴

California

California hosts Indo-Pacific-focused Navy, Marine Corps, Air Force, and Space Force installations, including Naval Base San Diego, Marine Corps Base Camp Pendleton, Travis Air Force Base, and Vandenberg Space Force Base. These sites are used to base Navy vessels and specialized units (including most of the Naval Surface Force, U.S. Pacific Fleet, one submarine squadron, four Sea-Air-Land (SEAL) teams, and the 30^th Naval Construction Regiment), Marine Corps ground units (including the 1^st Marine Division and the 1^st Marine Logistics Group), Navy, Marine Corps, and Air Force aircraft (including Navy fighter, command and control, and helicopter squadrons; Marine Corps fighter, tiltrotor, and helicopter squadrons; and Air Force reconnaissance, refueling, and airlift squadrons), and a Space Force Delta. DOD also uses defense infrastructure in California for training and large-scale RDT&E activities, to conduct space launches, and provide ballistic missile defense.³⁵

Hawaii

Hawaii hosts Army, Navy, Marine Corps, and Air Force installations, including Schofield Barracks, Joint Base Pearl Harbor-Hickam, and Marine Corps Base Hawaii. These sites are used to base Army ground units (including the 25^th Infantry Division), Navy vessels (including destroyers, cruisers, and attack submarines), Marine Corps ground units (including the 3^rd Marine Littoral Regiment), and Marine Corps, and Air Force aircraft (including Air Force fighter and airlift squadrons and Marine Corps helicopter, tiltrotor, and UAV squadrons). DOD also uses sites in Hawaii to conduct training and large-scale RDT&E activities and store and distribute fuel.³⁶ Defense infrastructure in Hawaii has been the subject of attention from policymakers and analysts in part because of a highly publicized leak from the Red Hill Bulk Fuel Facility in November 2021. Subsequent to the reported leak and defueling plan, the condition of facilities in the state has featured in a November 2022 report on Army infrastructure by the Congressional Budget Office (CBO).³⁷

West of the International Date Line

This report identifies 40 bases west of the IDL that support Indo-Pacific defense functions (see Figure 4 below).

Figure 4. U.S. Defense Sites, West of the International Date Line

Source: CRS graphic based on analysis of DOD information, including the "FY2022 Base Structure Report," installation and unit web pages, and related documentation. Notes: Naval Communications Station Harold E. Holt is not depicted due to space constraints.

Wake Island

Wake Island (an unincorporated U.S. territory) hosts Wake Island Airfield, an Air Force installation that supports trans-Pacific military air traffic as well as missile test activities.³⁸

Guam and the Northern Mariana Islands

Guam (an unincorporated U.S. territory) hosts Navy, Marine Corps, and Air Force installations, including Naval Base Guam, Marine Corps Base Camp Blaz, and Andersen Air Force Base (all managed jointly as Joint Region Marianas). These sites are used to base Army and Marine Corps ground units (including an Army Terminal High Altitude Area Defense Battery and future Marine ground units), Navy vessels (including one submarine squadron), and rotational deployments of Air Force bomber aircraft.³⁹ Since 2011, Guam has attracted a considerable amount of attention from policymakers and analysts as a strategic hub for U.S. military operations in the Indo-Pacific. DOD's infrastructure investments have undergone a significant increase over the past decade.⁴⁰

The Northern Mariana Islands (a U.S. commonwealth and unincorporated territory) hosts a number of sites that are used to support training and exercise activities, including the Marianas Island Range Complex and Tinian International Airport.⁴¹ DOD is also constructing new infrastructure to allow increased usage of the Northern Mariana Islands in support of ACE and related requirements.⁴²

The Marshall Islands, Micronesia, and Palau

The Marshall Islands, Micronesia, and Palau (commonly referred to as the Compacts of Free Association, or COFA, states) host an Army installation used for missile defense-focused RDT&E activities (Army Garrison-Kwajalein Atoll) and a site to support the planned installation of an Air Force radar system.⁴³ Some defense analysts and policymakers hold that the importance of the COFA states is increasing, due to their strategic location and potential to support U.S. capabilities in the event of a regional contingency.⁴⁴

Japan (Mainland)

Mainland Japan hosts Army, Navy, Marine Corps, and Air Force installations, including Camp Zama, Fleet Activities Yokosuka, Marine Corps Air Station Iwakuni, and Yokota Air Base. These sites are used to base and support Army ground and aviation units, Navy vessels (including an aircraft carrier, destroyers, cruisers, and amphibious assault ships), and Navy, Marine Corps, and Air Force fighter, electronic attack, command and control, tanker, and airlift aircraft. DOD also uses defense infrastructure in mainland Japan to detect and intercept missile threats, maintain and repair surface warships and submarines, and conduct training and exercises.⁴⁵

Japan (Okinawa)

Okinawa is a Japanese prefecture consisting of approximately 49 inhabited islands located about 400 miles southwest of mainland Japan.⁴⁶ It hosts Army, Marine Corps, and Air Force installations, including Army Garrison Okinawa, Marine Corps Base Camp Butler, and Kadena Air Base. These sites are used to base and support Marine Corps units (including the III Marine Expeditionary Force) and Marine Corps and Air Force fighter, tilt-rotor, rotary wing, airlift, and aerial refueling aircraft. DOD also uses sites on Okinawa to conduct training and exercises specific to jungle environments and support fuel storage and distribution functions.⁴⁷ DOD installations on Okinawa also 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.⁴⁸

According to the Okinawan Prefectural Government, as of 2018 approximately 70% of the "areas exclusively used by U.S. forces" in Japan were located on Okinawa.⁴⁹ The large U.S. defense infrastructure footprint on Okinawa has generated significant controversy among sections of the Okinawan public, and—pursuant to an agreement between the U.S. and Japanese governments—DOD is in the process of shifting thousands of Marines from bases in Okinawa to Guam's Marine Corps Camp Blaz.⁵⁰

Republic of Korea

The Republic of Korea (ROK; also referred to as South Korea) hosts Army, Navy, Marine Corps, and Air Force installations, 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. As noted above, following a 2004 bilateral agreement between the ROK and U.S. governments, 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.⁵¹ Unlike in other locations west of the IDL, U.S. basing posture in South Korean is primarily organized around deterring and resisting potential DPRK aggression.

The Philippines

The Philippines allows the U.S. DOD to deploy military forces at nine Philippine defense sites spread across the country. This access is governed by the Enhanced Defense Cooperation Agreement (EDCA), a bilateral agreement between the Philippines and the United States initially signed in 2014 and expanded in 2023.⁵² Per the EDCA text, U.S. access 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."⁵³ The increasing U.S. defense presence in the Philippines has generated some controversy among the Philippine public and certain elected officials (particularly the extent to which it is perceived to be directed against the PRC).⁵⁴

Singapore

Singapore allows the U.S. DOD to maintain a small presence known as Navy Region Center Singapore primarily to provide logistical support for visiting surface warships. This access is governed by the 1990 Memorandum of Understanding Regarding United States Use of Facilities in Singapore, a bilateral agreement between Singapore and the United States initially signed in 1990 and renewed in 2019.⁵⁵ Changi Naval Base and Sembawang shipyard are the largest Singaporean support facilities to which the U.S. Navy has access, while Paya Lebar Air Base hosts rotational U.S. Air Force personnel and aircraft.⁵⁶

Australia

Australia allows the U.S. DOD to rotationally deploy a number of ground and air forces to bases within the country, including a rotational U.S. Marine Air Ground Task Force known as Marine Rotational Force-Darwin (at Royal Australian Air Force Base Darwin and Robertson Barracks) and rotational deployments of U.S. Air Force bombers and fighters under the Enhanced Air Cooperation (EAC) initiative.⁵⁷ Additionally, as part of the Australia-United Kingdom-U.S. (AUKUS) pact, U.S. and U.K. nuclear-powered submarines will begin rotational deployments to Australia's HMAS Stirling naval base in 2027 (U.S. submarines will also reportedly increase the frequency of visits to this base beginning in 2023).⁵⁸ DOD's increasing presence in Australia is widely seen as a response to worsening relations between U.S.-aligned countries and the PRC.⁵⁹

British Indian Ocean Territory (Diego Garcia)

The British Indian Ocean Territory (commonly referred to as Diego Garcia; a British Overseas Territory) hosts Naval Support Facility Diego Garcia, a U.S. Navy-operated installation that primarily provides logistical support for U.S. and allied forces operating in and around the Persian Gulf and Indian Ocean. The site that would become Naval Support Facility Diego Garcia was established by a secret bilateral agreement reached between the U.S. and British governments in 1966; it has been the subject of some controversy owing to the claims of indigenous Chagos Islanders forcibly displaced during the base's construction.⁶⁰

Other Indo-Pacific Sites

In addition to the locations described above, DOD has used a number of other sites west of the International Date Line to base and support military forces. For example, Thailand's location and relations with the United States have led U.S. forces to use a number of Thai defense sites on a rotational basis (e.g., U-Tapao Royal Thai Navy Air Field).⁶¹ U.S. Navy vessels also routinely conduct visits at a wide array of Indo-Pacific regional ports.⁶² Some analysts have also speculated that, in the event of PRC military action against Taiwan, the United States may base significant forces in Taiwan.⁶³

Issues for Congress

Indo-Pacific Basing Posture

Congress may consider the degree to which the current U.S. basing posture—that is, the geographical and functional distribution of bases in the Indo-Pacific region—supports strategic priorities and operational requirements, under both peacetime and wartime conditions. Despite considerable geopolitical, technological, and doctrinal change in recent years, much of DOD's basing posture remains, at least in part, the product of decisions made decades previously. According to some observers, this has led to a misalignment between regional defense infrastructure and the demands of the current and future threat environment. As one analyst framed the problem in a 2022 editorial

After more than a decade of promising to improve the survivability of U.S. forces in the Indo-Pacific, the department has little to show for it. In part, ongoing wars in the Middle East have inhibited efforts to rebalance the American military footprint to the Pacific, as has the need to obtain the consent of nations that host American forces. Additionally, the services prefer to fund their priority weapons, and their reticence to spend money on supporting infrastructure is compounded when uncertainty about future base access is factored in. Finally, the Defense Department has yet to break with its past approach to power projection and to fully flesh out new operational concepts and ways of fighting.⁶⁴

The basing posture issues for Congress may be divided into three distinct but related questions:

• 1. Where should U.S. bases be maintained or established?
• 2. To what extent should DOD distribute—or consolidate—regional basing functions?
• 3. How resilient do U.S. bases need to be, and how can DOD improve infrastructure resilience (to the extent it falls short of congressional goals)?

Placement

A fundamental question with respect to basing posture is that of placement—to achieve national strategic aims and meet attendant operational requirements, where in the Indo-Pacific should the United States operate military bases? In addressing this question, Congress may weigh the tradeoffs between the advantages that proximity to likely operational areas could create for U.S. combat forces (especially air and naval), on the one hand, and the vulnerability such proximity could produce for U.S. forces and infrastructure, on the other. Congress may also consider factors such as the political and military reliability of countries hosting U.S. bases, as well as the potential for significant posture changes to affect regional stability.

Although the President, as Commander-in-Chief, is ultimately responsible for the establishment and disestablishment of military bases, Congress may legislate requirements, restrictions, and other guidance (for instance, Congress has played a major role in shaping the Base Realignment and Closure, or BRAC, process).⁶⁵ Historically, this has tended to occur as part of the annual defense authorization and appropriations processes.

As described above, locating military bases close to likely operational areas reduces the transit time and resources required for U.S. forces to conduct combat operations in those areas. This is especially significant for fighter and bomber aircraft, as their combat radii (the effective distance an aircraft can fly, fight, and return) are constrained by the amount of fuel they can carry.⁶⁶ Thus, sites such as Okinawa's Kadena Air Base (located approximately 400 miles from Taiwan, well within the combat radius of relevant U.S. fighter and bomber aircraft) may be attractive to military planners as convenient bases for air operations. However, the geography of the Indo-Pacific is such that proximity to the areas of a prospective contingency—Taiwan being the most prominent, but also areas of the South China Sea, the Korean peninsula, and parts of the Indian Ocean—entails proximity to adversary air and missile strike capabilities. As Figure 5 below illustrates, South Korea, most of Japan, and the northern portions of the Philippines may be within range of PRC and DPRK short or medium-range ballistic missiles, while Guam and parts of Japan, the Philippines, and Australia may be within range of PRC intermediate-range ballistic missiles.

Figure 5. Regional Missile Threat Notional ranges of PRC ballistic missiles and U.S. regional defense sites

Source: CRS graphic based on PRC missile data and analysis from "Missiles of China," Center for Strategic and International Studies Missile Threat Project, April 12, 2021, at https://missilethreat.csis.org/country/china and CRS analysis of DOD basing data. Notes: Ranges are notional.

Some of the consequences of regional infrastructure placement for U.S. military performance are explicitly examined in two studies of a hypothetical U.S.-China war. In an August 2022 report ("Can China Take Taiwan? Why No One Really Knows"), Brookings Institute analyst Michael O'Hanlon evaluated whether the PRC could successfully conquer Taiwan. Using open-source data and estimates on Chinese and U.S. orders of battle, weapons capabilities and inventories, and doctrine, O'Hanlon modelled two scenarios for a U.S.-China conflict over Taiwan: "a maritime fight centered on submarines" (Scenario 1); and "a broader subregional war" (Scenario 2). In both scenarios, regional U.S. bases play a role. In Scenario 1, O'Hanlon speculates that air bases in Japan may be used to host anti-submarine (ASW) and fighter aircraft for use against Chinese maritime and air platforms enforcing a blockade of Taiwan, while in Scenario 2, O'Hanlon models the use of U.S. and allied bases in Japan and Guam to launch air and naval operations against Chinese maritime, air, and ground platforms, personnel, and infrastructure in and around Taiwan and mainland China.⁶⁷ Given their role in enabling U.S. combat operations, these bases would likely come under Chinese attack—especially in a situation resembling O'Hanlon's Scenario 2, which sees aircraft and land-based missiles striking U.S. installations in mainland Japan, Okinawa, and Guam, with a high probability of destroying or damaging most infrastructure targets.⁶⁸

In a January 2023 report, three analysts at the Center for Strategic and International Studies (CSIS) summarized the results and implications of a wargame simulating the initial phases of a U.S.-China war precipitated by an invasion of Taiwan.⁶⁹ Using open-source data and estimates, CSIS developed and ran 24 iterations of a wargame under "base case," "pessimistic," and "optimistic" parameters. As in the Brookings study described above, the U.S. sought to support air and naval operations in and around Taiwan and mainland China from bases in Japan and Guam, and the PRC sought to deny the use of those bases through kinetic attacks. In most of the "pessimistic" and "base case" iterations, U.S. air bases in mainland Japan, Okinawa, and Guam were subjected to effective Chinese missile attacks, damaging infrastructure and causing the majority of U.S. combat aircraft losses.⁷⁰

The debate over basing fighter aircraft at Kadena Air Base (AB) on Okinawa provides another illustration of this dynamic. In October 2022, the Air Force announced that it would begin a phased withdrawal of two F-15C and D fighter squadrons formerly based at Kadena AB.⁷¹ The withdrawal, to be accomplished in phases over a two-year period, faced criticisms from some analysts concerned the move might undermine regional deterrence (several Members of Congress delivered a letter to the Secretary of Defense alleging the move would create a "tangible reduction in American forward combat power").⁷² However, others have defended the move, arguing that Chinese strike capabilities make Kadena "uniquely ill-positioned for permanently basing large numbers of American aircraft" and instead advocating for a more geographically dispersed and rotational approach to regional basing.⁷³

Congress may assess the tradeoffs between the proximity of defense sites to likely operational areas and the resultant vulnerability to adversary attack. This assessment could in turn inform congressional direction to DOD regarding the implementation of basing posture, as well as congressional prioritization of defense outlays.

In considering the question of base placement, Congress may also note that DOD's regional basing posture—along with its broader force posture—has remained broadly consistent over the past three decades.⁷⁴ As the Brookings Institute's Andrew Yeo and Michael O'Hanlon observe in a February 2023 report

Broadly speaking, the U.S. force posture in the Pacific looks very much like it did in the mid-1990s, with the preponderance of America's 100,000-strong troop presence there concentrated in Japan and South Korea. Since that time, the only major changes involving thousands of forces have been the reduction in the U.S. Army presence in South Korea by about 10,000 in the early 2000s and the more recent gradual shift of about half of the 18,000 U.S. Marines on Okinawa to Guam.⁷⁵

Although the number and distribution of DOD-operated installations has remained broadly consistent since the mid-1990s, one way that the United States has sought to expand its regional infrastructure footprint has been through the negotiation of access to bases operated by allied or partner governments (an approach sometimes termed 'places not bases').⁷⁶ Since 2011, DOD has increased regional deployments to Australian sites (particularly in the Northern Territory and Queensland) and, under the U.S.-Philippines Enhanced Defense Cooperation Agreement (EDCA), secured access on a rotational basis to nine Philippine military bases (mainly on the northern islands of Luzon and Palawan).⁷⁷ Despite this expansion, some observers have identified areas of the Indo-Pacific where U.S. presence and access could be increased. Yeo and O'Hanlon write that "a particularly large hole in U.S. force posture exists in Southeast and South Asia where basing access agreements remain limited," and identify the pursuit of basing rights in the area as a potential option for policymakers.⁷⁸

A related issue for congressional consideration is the degree to which the United States may rely upon countries hosting U.S. military bases to allow access in the event of a contingency. For example, the importance of Philippine bases to U.S. plans for a potential conflict has grown considerably over the past decade—so much so that, as former PACOM commander Admiral (Ret.) Harry Harris stated in 2023 before the House Armed Services Committee, "it's hard to imagine a fight with the PRC without being able to use bases on the Philippines."⁷⁹ Statements by Philippine officials in 2022 and 2023—including President Ferdinand Marcos Jr.—suggest that permission for U.S. forces to operate from these bases would be granted only under certain circumstances, and that DOD will not be permitted to undertake "offensive action" from EDCA sites.⁸⁰

Although this concern may be especially pronounced for countries that now host U.S. forces at non-DOD-operated facilities (such as the Philippines and Singapore), some commentators have also posited that even countries that have hosted DOD-operated facilities for decades, such as South Korea or Japan, may impose limits on U.S. usage of bases to avoid provoking Chinese attacks.⁸¹ Congress may consider the appropriate balance of risk, as well as direct planning for alternate basing options in the event of such a situation. Congress may also consider the appropriate level of infrastructure investment in sites to which future DOD access may be uncertain.⁸²

Finally, Congress may consider how changes in basing posture affect broader geopolitical developments in the Indo-Pacific. Among international relations scholars, the concept of the security dilemma—a problem in which states, by taking measures to improve their own security, may threaten others—occupies a central role. Some commentators have argued that this dynamic exists in the contemporary Indo-Pacific, and that U.S. basing is a factor:

The same dynamic [i.e., the security dilemma] is operating in Asia. Not surprisingly, China regards America's long position of regional influence—and especially its network of military bases and its naval and air presence—as a potential threat. As it has grown wealthier, Beijing has quite understandably used some of that wealth to build military forces that can challenge the U.S. position… Each side's efforts to deal with what it regards as a potential security problem merely reinforced the other side's own security fears, thereby triggering a response that strengthened the former's original concerns. Each side sees what it is doing as purely defensive reaction to the other side's behavior, and identifying "who started it" soon becomes effectively impossible.⁸³

PRC officials have strongly criticized recent U.S. moves to expand its regional defense infrastructure footprint, alleging that measures such as the addition of new sites to the U.S.-Philippines EDCA "are part of U.S. efforts to encircle and contain China" and will "endanger regional peace and stability."⁸⁴ On the other hand, some policymakers and analysts have argued that establishing additional bases could strengthen U.S. deterrence of PRC aggression and thereby decrease the likelihood of a crisis.⁸⁵ In weighing whether to establish additional bases, Congress may consider potential effects on Indo-Pacific stability.⁸⁶

Organization

Aside from the question of where to maintain or seek basing more generally, Congress may also consider issues relating to base organization and operation. Historically, DOD has created larger, consolidated installations in the Indo-Pacific, clustering many defense functions within mainly DOD-operated sites. However, as described above, the Army, Air Force, Navy, and Marine Corps have each begun to develop and implement new concepts for more distributed combat and logistical operations. These operational concepts propose a different use of infrastructure, one in which larger, permanent, and concentrated bases are supplemented by—and, in some cases, replaced or used interchangeably with—smaller, temporary, non-U.S.-operated, or distributed facilities.⁸⁷

As an example of how these shifts may affect regional basing posture, CSIS senior fellow Bonny Lin offered the following characterization of Indo-Pacific infrastructure in a February 2023 Senate Armed Services Committee hearing:

Our infrastructure in the Indo-Pacific, particularly the fact that we are now investing in more resilient and dispersed basing is absolutely critical, particularly as we look at the range of [PRC] missiles…The range of missiles that China can bring to bear means that in any fight over Taiwan, we will need to be able to disperse our assets so we're not reliant on any particular base. And in order to be able to maintain that… we need to harden our infrastructure. We also need to work with our allies and partners to make sure that we have the capabilities to quickly repair, for example, runways and other facilities.⁸⁸

To some extent, this conceptual perspective is manifested in DOD doctrine for—and investments in—regional infrastructure. For example, in a March 2023 interview, the commander of Pacific Air Forces (PACAF) stated that "from the Agile Combat Employment standpoint, what we're spending our dollars on this year is expanding the number of places that we can go to, and of the places that we're already at [sic], expanding the capability at those places."⁸⁹

However, some analysts have identified potential drawbacks to a more distributed basing posture. A January 2023 report by the RAND Corporation found that operating from more dispersed air bases could pose significant sustainment and communication challenges, and cautioned that such bases "may not be more survivable than those closer to the threat if the farther bases can be brought down by a small number of missiles" due to their smaller size or a lack of protective systems and infrastructure.⁹⁰

Congress may consider the costs and benefits of a more distributed approach to regional basing functions, assess the extent to which DOD is implementing such an approach, and deliberate on the desirability of additional investments to modify the concentration or distribution of base facilities.

Resilience

Another aspect of posture Congress may consider is the resilience—broadly defined as the ability to resist, adapt to, and recover from disruption—of Indo-Pacific installations.⁹¹ Given the regional environment described above, DOD has tended to structure its resilience efforts around the threat of kinetic attack, particularly by PRC air and missile capabilities.

When it comes to protecting bases from air and missile attacks, analysts typically distinguish between active and passive defenses. Active defenses are measures that seek to neutralize incoming threats before they are able to strike their targets—whether by kinetic interception, as with the THAAD or PATRIOT missile defense systems, or through the use of newer technologies like directed energy and microwave-based countermeasures.⁹² Passive defenses are measures intended to decrease the damage, disruption, and general impact of adversary attacks, and may include the construction of protective physical structures (e.g., hardened aircraft shelters), the development of repair and damage control capabilities, and practices such as the dispersal or concealment of vulnerable assets.⁹³

The appropriate balance between active and passive defenses has been the subject of debate among policymakers and commentators. Some analysts, such as the Hudson Institute's Rebeccah Heinrichs, emphasize the centrality of active defenses:

While passive defenses including tactics intended to deceive an adversary and fortification of military infrastructure to sustain an attack are important, there is no substitute for a layered active defense. To achieve cost-effectiveness, some budget offices may be tempted to over-rely on passive defenses, but that would be a grave mistake. The US military must have the ability to blunt the impact of a fast PRC attack, and that means preventing missiles from hitting key targets.⁹⁴

Other analysts maintain that active defenses, while useful, can be expensive and vulnerable to attack. A January 2023 study by the RAND Corporation argues that

the most-cost-effective ways to improve air base resilience are robust, passive defenses…[including] hardened shelters for aircraft; dispersal of aircraft; redundant fuel supplies; prepositioned munitions; rapid runway repair capabilities; and tailored forms of camouflage, concealment, and deception.⁹⁵

The publicly available studies and wargames that examine a potential conflict with a strategic competitor suggest that the resilience of Indo-Pacific installations—particularly air bases—may be a factor in such a conflict's outcome.⁹⁶

Congress may assess the desirability and efficacy of additional investments in resilience-building measures at Indo-Pacific bases, and weigh the respective benefits of active and passive defenses.

Resourcing Regional Defense Infrastructure

Congress funds the establishment and sustainment of defense infrastructure through the Military Construction and Operation and Maintenance appropriations titles. In addition, beginning in FY2021, Congress has authorized a particular set of Indo-Pacific defense infrastructure appropriations as part of the Pacific Deterrence Initiative (PDI), a group of regionally-focused defense investments and activities typically included as part of the annual National Defense Authorization Act (NDAA).

Military Construction

Military construction (MILCON) appropriations fund construction, development, conversion, or extension activities carried out with respect to a military installation, as well as any DOD acquisitions of real property (for more information on MILCON authorities and activities, see CRS Report R44710, Military Construction: Authorities and Processes).

Over the past four fiscal years, annual military construction appropriations for Indo-Pacific sites have ranged from a low of $1.37 billion to a high of $3.54 billion (see Table 1 below).

As Table 1 illustrates, the proportion of MILCON appropriations funding projects at Indo-Pacific sites has every fiscal year since FY2020. In FY2023, selected Indo-Pacific bases with projects receiving MILCON appropriations included⁹⁷

• Fort Wainwright, Alaska ($99 million for a physical fitness center annex);
• Joint Base Elmendorf-Richardson ($63 million for an aircraft maintenance hangar);
• Clear Space Force Station, Alaska ($68 million for a new dormitory);
• Joint Base Elmendorf-Richardson, Alaska ($100 million to extend runway 16/34);
• Naval Air Station Whidbey Island, Washington ($68.1 million for airfield pavement improvements);
• Camp Pendleton, California ($85.2 million for Basilone Road Realignment);
• Twentynine Palms ($120.4 million for a range simulation training and operations facility);
• Naval Air Station Lemoore, California ($201.3 million for F-35C maintenance hangar and airfield pavement);
• Vandenberg Space Force Base, California ($89 million for consolidated maintenance facility);
• Naval Base Coronado, California ($75.7 million for a SOF operations support facility);
• Schofield Barracks, Hawaii ($111 million for the construction of company operations facilities);
• Joint Base Pearl Harbor-Hickam, Hawaii ($621.2 million for the replacement of Dry Dock 3 and $103.4 million for the construction of missile magazines);
• Marine Corps Base Hawaii, Hawaii ($87.9 million for bachelor enlisted quarters);
• Naval Base Guam, Guam ($131.6 million for 9^th Engineer Support Battalion equipment and maintenance facility and $149.3 million ground combat element infantry battalion 1 and 2 facilities);
• Tinian, Northern Mariana Islands ($58 million for airfield development and $92 million for fuel tanks);
• Army Garrison-Kwajalein Atoll, Marshall Islands ($69 million for a medical clinic);
• Kadena Air Base, Japan ($94.1 million for Marine Corps bachelor enlisted quarters, $101.3 million for a Marine Corps barracks complex, $71 million for a helicopter operations maintenance hangar, and $77 million for a theater a/c corrosion control center);
• Marine Corps Air Station Iwakuni, Japan ($85 million for bulk fuel storage tanks);
• Yokota Air Base, Japan ($72.2 million for operations and warehouse facilities); and
• Royal Australian Air Force Base Darwin, Australia ($72.4 million for aircraft parking apron).

Although Indo-Pacific military construction appropriations have increased in both absolute and proportional terms since FY2020, some analysts and Members of Congress argue that regional MILCON activities have been insufficient to meet U.S. requirements. In the joint explanatory statement accompanying the FY2023 Military Construction, Veterans Affairs, and Related Agencies Appropriations Act, the Committees expressed concern that "the Services have not properly prioritized projects within INDOPACOM in recent fiscal years, instead choosing to fund projects that are specifically beneficial to the Service and not necessarily the joint mission."⁹⁸ Some commentators attribute what they consider insufficient MILCON funding to structural factors. In a 2022 piece for War on the Rocks, for example, three analysts at the Center for a New American Security argued that Indo-Pacific infrastructure upgrades "have been habitually shortchanged because the services prefer to invest in force structure and Congress does not like spending money overseas."⁹⁹

Congress may consider assessing whether the level of funding for Indo-Pacific military construction projects provided in recent appropriations acts is adequate (in both absolute terms and as a proportion of overall MILCON spending) to meet current and future military requirements, particularly if significant changes to basing posture are anticipated.

Facilities Sustainment, Restoration, and Modernization

A number of analysts, DOD officials, and Members of Congress have expressed concern about the condition of Indo-Pacific defense infrastructure. In a February 2023 Senate Armed Services Committee hearing, for example, Senator Mazie Hirono (HI) offered the following characterization of the challenges facing DOD infrastructure:

"Clearly, there are many demands on our resources—that is an understatement—and I would consider a foundational concern to be the need to invest in our infrastructure, which is not only a matter of geopolitical competition, but also the readiness of the forces… In the last year, there have been numerous issues with the military's infrastructure in Hawaii—from water main breaks to toxic chemical leaks and spills endangering our groundwater. And I know that these kinds of events are not particular to Hawaii. Across the country, we need to better maintain and modernize our DOD infrastructure to take care of our people, get our systems out of maintenance on time, and be able to support national security."¹⁰⁰

Although the Indo-Pacific region has experienced several high-visibility infrastructure problems (e.g., the Red Hill Bulk Fuel Storage Facility leak), the issue of poor infrastructure condition is not unique to the region.¹⁰¹ In a 2022 report, the Government Accountability Office found that DOD had a deferred maintenance backlog that would require at least $130 billion to eliminate, creating "significant risk to [the Department's] objective of maintaining facilities in good working order to meet working requirements."

Facilities sustainment, restoration, and modernization (FSRM) activities on military installations are funded by Operation and Maintenance (O&M) appropriations. Unlike MILCON spending, FSRM funding information—as documented in DOD budget requests and congressional authorization and appropriation legislation—is not typically disaggregated by specific locations or installations, making it difficult to assess the level of funding by site or region.¹⁰² In FY2023, Congress appropriated approximately $16.8 billion for FSRM activities across DOD, with the Army (approximately $5.1 billion), Air Force (approximately $4.4 billion), and Navy (approximately $4 billion) receiving the largest amounts, respectively.¹⁰³

Given the strategic and operational importance of Indo-Pacific defense sites, Congress may assess the extent to which more detailed budget reporting by DOD, adjustments to FSRM funding, or further studies of related infrastructure issues may be necessary to meet military requirements.

Pacific Deterrence Initiative

In FY2021, Congress established the Pacific Deterrence Initiative (PDI), a set of prioritized defense investments and activities intended to "enhance the United States deterrence and defense posture in the Indo-Pacific region, assure allies and partners, and increase capability and readiness in the Indo-Pacific region."¹⁰⁴ PDI is not a separate funding source; rather, its purpose is to "focus resources on capability gaps" and "enhance budgetary transparency and oversight" by identifying and collating Indo-Pacific-focused spending and programs from the broader DOD budget.¹⁰⁵

In FY2022 and FY2023, activities authorized under PDI were divided into five categories:

• Presence and Posture ($4.1 billion authorized in FY2022, $6.46 billion authorized in FY2023);
• Logistics and Prepositioning of Equipment ($360 million authorized in FY2022, $500 million authorized in FY2023);
• Exercises, Training, and Experimentation ($696 million authorized in FY2022, $2 billion authorized in FY2023);
• Defense and Security Capabilities of Allies and Partners ($489 million authorized in FY2022, $732 million authorized in FY2023); and
• Infrastructure Improvements ($1.5 billion authorized in FY2022, $1.8 billion authorized in FY2023)

The Infrastructure Improvements category includes authorizations for projects funded through both military construction (MILCON) and operation and maintenance (O&M) appropriations. Examples of authorized PDI projects under this category include

• Bulk storage tanks at MCAS Iwakuni (FY2023, $85 million, MILCON);
• Aircraft parking apron at RAAF Base Darwin, Australia (FY2023, $72.4 million, MILCON);
• Fuel tanks with pipeline and hydrant system on Tinian, Northern Mariana Islands (FY2023, $92 million, MILCON);
• Japan vehicle maintenance shop (FY2023, $80 million, MILCON);
• Air Force infrastructure improvements (FY2022 and FY2023, $404.3 million and $412.4 million, O&M);
• Marine Corps FSRM (FY2022 and FY2023, $112.1 million and $127.2 million, O&M);
• Corrosion control hangar for C-130J at Yokota Air Base (FY2022 and FY2023, $67 million and $10 million, MILCON);
• Joint Communication Upgrade at Naval Base Guam (FY2022, $84 million, MILCON); and
• Extended runway at JBE-R (FY2022, $79 million, MILCON).¹⁰⁶

With respect to PDI generally, some analysts and Members of Congress have contended that DOD implementation of PDI priorities has been misaligned with congressional intent.¹⁰⁷ In the National Defense Authorization Acts (NDAAs) for FY2022 (P.L. 117-81) and FY2023 (P.L. 117-263), PDI authorizations differed significantly from DOD requests, with Congress redistributing or adding billions of dollars in proposed PDI investments. The FY2023 House Appropriations Committee report (H.Rept. 117-388) expressed "concern that DOD has failed to provide adequate accounting for the funding requested" under PDI, and directed DOD to augment the budgetary and programmatic descriptions of PDI activities in its FY2024 budget documentation.

With respect to infrastructure more specifically, there were also considerable discrepancies between

• the FY2023 spending DOD requested under the "Infrastructure Improvements" category ($1.21 billion);
• the FY2023 spending INDOPACOM requested under the "Infrastructure, Responsiveness, and Resilience" category as part of a congressionally mandated report separate from DOD's formal budget request ($726 million); and¹⁰⁸
• the FY2023 spending Congress authorized for PDI in the FY2023 NDAA ($1.8 billion).

Additionally, the criteria according to which DOD categorizes infrastructure activities in its budget requests are unclear. Although there is an "Infrastructure Improvements" category, in its FY2023 PDI budget documentation DOD requested funding for infrastructure-related activities (i.e., MILCON and FSRM) under four of the six PDI categories.¹⁰⁹ As an example, a combined $129 million of MILCON funding was requested for bulk fuel storage tanks at Marine Corps Air Station Iwakuni and Yokota Air Base under the "Improved Logistics, Maintenance, and Prepositioning" category, while $39 million of MILCON funding was requested for missile defense infrastructure under the "Modernized and Strengthened Presence" category.

Congress may consider whether modifications to PDI are desirable to: clarify the purpose and intent of activity categories; increase the detail that DOD provides in its congressional documentation; and ensure that infrastructure activities are aligned with strategic aims and military requirements (especially those created by the implementation of new operational concepts).

Appendix A. Key Sites and Facilities

This appendix provides descriptions of key sites and facilities covered by this report, as well as a consolidated list of major Indo-Pacific bases (see Table A-1 below).

Alaska

Fort Wainwright. Fort Wainwright is an Army installation located in Fairbanks, AK. It occupies approximately 756,530 acres, and hosts the 1^st Infantry Brigade, 11^th Airborne Division (an infantry brigade combat team) as well as the 1^st Battalion, 25^th Aviation Regiment (an AH-64 Apache attack reconnaissance battalion) and the 1^st Battalion, 52^nd Aviation Regiment (a general support aviation battalion with UH-60 Blackhawks, CH-47 Chinooks, and UH-60 medevac support).¹¹⁰

Fort Greely. Fort Greely is an Army installation located about 100 miles southeast of Fairbanks, AK. It occupies approximately 7,200 acres, and supports midcourse missile defense.¹¹¹ It hosts the Ground-Based Midcourse Defense anti-ballistic missile interception system, the 49^th Missile Defense Battalion, 100^th Missile Defense Brigade (which operates and secures the ground-based midcourse defense system), the 59^th Signal Battalion (which conducts strategic signal operations for missile command), and the Cold Regions Test Center (which tests materiel and equipment in cold weather conditions).¹¹²

Joint Base Elmendorf-Richardson (JBER). JBER is a joint Army-Air Force installation located near Anchorage, AK. It occupies approximately 73,000 acres, and hosts the Army's 2^nd Infantry Brigade, 11^th Airborne Division, (an airborne brigade combat team), as well as the Air Force's 11^th Air Force and 3^rd Wing, which consists of two F-22 fighter squadrons, one E-3 command and control squadron, and one mixed C-17/C-12 airlift squadron. In addition, JBER is also home to the Alaska Air National Guard's 176^th Wing, which includes three HH-60 and HC-130 rescue squadrons and two C-17 airlift squadrons.¹¹³

Eielson Air Force Base. Eielson Air Force Base is an Air Force installation located near Fairbanks, Alaska. It occupies approximately 24,900 acres, and hosts the 354^th Operations Group, which includes two F-35 fighter squadrons and one F-16 squadron.¹¹⁴

Clear Space Force Station. Clear Space Force Station is a Space Force installation located about 75 miles southwest of Fairbanks, AK. It occupies approximately 11,400 acres, and hosts the 13^th and 213^th Space Warning Squadrons, which provide missile warning and defense as well as space domain awareness.¹¹⁵

Other sites. In addition to the five installations detailed above, Alaska is home to the Northern Warfare Training Center, an Army training site in Black Rapids, AK that provides training for cold weather and mountain environments; the COBRA DANE L-band missile defense radar site located in Shemya, AK; and several auxiliary airfields, including Eareckson Air Station in Shemya, AK.¹¹⁶

Washington

Joint Base Lewis-McChord (JBLM). JBLM is a joint Army-Air Force installation, consisting of a main base area, located about nine miles southwest of Tacoma, WA and the Yakima Training Center, located near Yakima, WA. The main base area occupies approximately 87,000 acres, while the Yakima Training Center occupies approximately 323,000 acres.¹¹⁷ JBLM serves as the headquarters for the Army's I Corps, which encompasses about 44,000 soldiers in the Indo-Pacific region. Army units based at JBLM include the 7^th Infantry Division, the 1^st Multi-Domain Task Force, and the 5^th Security Force Assistance Brigade.¹¹⁸ JBLM also hosts the Air Force's 62^nd and 446^th Airlift Wings (Reserve), which together include six C-17 airlift squadrons, as well as the Western Air Defense Sector, a Washington Air National Guard unit responsible for regional air defense operations.¹¹⁹ JBLM's Yakima Training Center provides a large, versatile training area in a high desert environment, including 25 separate ranges.¹²⁰

Naval Base Kitsap. Naval Base Kitsap is a Navy installation on the Kitsap Peninsula in Washington. It occupies approximately 12,000 acres and hosts a wide array of facilities and tenant commands.¹²¹ Significant units and capabilities at Naval Base Kitsap include two Nimitz-class aircraft carriers (USS Nimitz and USS Theodore Roosevelt); three submarine squadrons (two ballistic and guided missile squadrons comprised of Ohio-class submarines and one development squadron comprised of Seawolf-class submarines); one unmanned undersea vehicle (UUV) development squadron; the Puget Sound Naval Shipyard and Intermediate Maintenance Facility (a Navy-owned and operated shipyard that maintains, upgrades, and retires naval vessels; the shipyard also includes Trident Refit Facility Bangor, which maintains and upgrades Indo-Pacific-based ballistic missile submarines); Strategic Weapons Facility Pacific (a facility that stores, maintains, and upgrades submarine-based nuclear weapons); and Manchester Fuel Depot (the largest underground DOD fuel storage facility on the West Coast, with an average annual throughput of 2.3 million barrels of fuel).¹²²

Naval Station Everett. Naval Station Everett is a Navy installation located in Everett, WA. The main base occupies approximately 217 acres, but the installation also includes the following noncontiguous areas: Naval Radio Station Jim Creek (responsible for communication with submarines operating in the Pacific); Naval Facility Pacific Beach (a training facility for naval aviators); and Naval Family Support Complex Smokey Point (a facility for family and morale, welfare, and recreation activities).¹²³ Naval Station Everett is the homeport for seven Arleigh Burke-class guided missile destroyers and two Coast Guard vessels (a coastal patrol boat and a buoy tender).¹²⁴

Naval Air Station Whidbey Island. Naval Air Station Whidbey Island is a Navy installation located near Oak Harbor, WA. It occupies approximately 7,200 acres, and hosts thirteen EA-18 electronic attack squadrons, five P-8 maritime patrol squadrons, two P-3 maritime patrol squadrons, and one EP-3 reconnaissance squadron.¹²⁵

Fairchild Air Force Base. Fairchild Air Force Base is an Air Force installation located about 12 miles west of Spokane, WA. It occupies approximately 4,300 acres, and hosts the Air Force's 92^nd Air Refueling Wing and the Washington Air National Guard's 141^st Air Refueling Wing, which operate KC-135 refueling aircraft.¹²⁶

California¹²⁷

Naval Air Station Lemoore. Naval Air Station Lemoore is a Navy installation located about 30 miles south of Fresno, CA. It occupies approximately 40,000 acres, and hosts three F-35 fighter squadrons and thirteen F/A-18 fighter squadrons.¹²⁸

Naval Base Ventura County. Naval Base Ventura County is a Navy installation located approximately 55 miles west of Los Angeles in Ventura County, CA. It is comprised of the three operating areas of Point Mugu, Port Hueneme, and San Nicolas Island, which together occupy approximately 19,400 acres. Significant units, facilities, and capabilities at Naval Base Ventura County include four E-2/D command and control squadrons, the 30^th Naval Construction Regiment (the Pacific 'Seabees'), Unmanned Surface Vessel (USV) Division One, and the Point Mugu Sea Range (a 36,000 square mile area for testing missiles, free-fall weapons, and electronic warfare systems).¹²⁹

Naval Base Coronado. Naval Base Coronado is a Navy installation in San Diego, CA. It is comprised of eight constituent sites: Naval Air Station North Island, Coronado; Naval Amphibious Base, Coronado; Naval Outlying Landing Field, Imperial Beach; Naval Auxiliary Landing Field, San Clemente Island; Silver Strand Training Complex-South; Camp Michael Monsoor Mountain Warfare Training Center; Camp Morena; and the Remote Training Site, Warner Springs. Together, these occupy over 57,000 acres and host a wide array of units and tenant commands, including sixteen helicopter squadrons, two fixed-wing squadrons, two Nimitz-class aircraft carriers, four Sea-Air-Land (SEAL) teams, and Commander, Naval Special Warfare Command (SPECWAR).¹³⁰

Naval Base San Diego. Naval Base San Diego is a Navy installation in San Diego, CA. It occupies approximately 1,600 acres, and serves as the homeport for most of the Naval Surface Force, U.S. Pacific Fleet (SURFPAC).¹³¹ In addition to 56 SURFPAC vessels (including destroyers, cruisers, littoral combat ships, amphibious transport docks, and other warships) Naval Base San Diego is also the homeport of the hospital ship USNS Mercy.

Naval Base Point Loma. Naval Base Point Loma is a Navy installation in San Diego, CA. It occupies approximately 1,100 acres and hosts several significant units and tenant commands. These include one submarine squadron (which includes four Los Angeles-class attack submarines), a floating dry dock (used to service submarines and smaller vessels), Commander U.S. 3^rd Fleet, Naval Information Warfare Systems Command (formerly known as SPAWAR), and Naval Mine and Anti-Submarine Warfare Command.¹³²

Marine Corps Air Station Miramar. Marine Corps Air Station Miramar is a Marine Corps installation in San Diego, CA. It occupies approximately 22,880 acres and hosts the 3^rd Marine Aircraft Wing's Marine Aircraft Groups 11 and 16, which together include two F/A-18C fighter squadrons, one F-35C fighter squadron, one KC-130 tactical aerial refueling squadron, four V-22 squadrons, and four CH-53 heavy helicopter squadrons.¹³³

Marine Corps Base Camp Pendleton. Marine Corps Base Camp Pendleton is a Marine Corps installation located approximately 38 miles north of San Diego, CA. It occupies approximately 125,000 acres, and serves as the headquarters of I Marine Expeditionary Force (MEF). I MEF subordinate commands and units based at Camp Pendleton include the 1^st Marine Division, the 1^st Marine Logistics Group, and the 3^rd Marine Aircraft Wing's Marine Aircraft Group 39 (which includes four attack helicopter squadrons and two V-22 squadrons).¹³⁴

Beale Air Force Base. Beale Air Force Base is an Air Force installation located approximately 45 miles north of Sacramento, CA. It occupies approximately 22,450 acres, and hosts the 9^th Reconnaissance Wing (which operates U-2 reconnaissance aircraft and RQ-4 reconnaissance unmanned aerial vehicles) and the Air Force Reserve's 940^th Air Refueling Wing (which includes a squadron of KC-135R aerial refueling aircraft).¹³⁵ Beale Air Force Base is also home to the Space Force's 7^th Space Warning Squadron, which operates an Upgraded Early Warning Radar system to detect and characterize sea-launched or intercontinental ballistic missile launches targeting North America.¹³⁶

Travis Air Force Base. Travis Air Force Base is an Air Force installation located approximately three miles east of Fairfield, CA. It occupies approximately 6,440 acres, and handles more cargo and passenger traffic than any other air base in the United States.¹³⁷ It hosts the 60^th Air Mobility Wing (which includes one C-17 airlift squadron, one C-5 airlift squadron, and two KC-10 refueling squadrons) and the Air Force Reserve's 349^th Air Mobility Wing (which includes one C-17 airlift squadron, one C-5 airlift squadron, and two KC-10 refueling squadrons).¹³⁸

Vandenberg Space Force Base. Vandenberg Space Force Base is a Space Force installation located in Santa Barbara County, CA. It occupies approximately 99,600 acres, and provides space launch and range capabilities for DOD, other U.S. government agencies, and commercial partners. Vandenberg Space Force Base is the home of Space Launch Delta 30, which operates sixteen on-site launch facilities and complexes.¹³⁹ Vandenberg Space Force Base also hosts ground-based interceptors to provide midcourse ballistic missile defense for western North America.¹⁴⁰

Hawaii

Joint Base Pearl Harbor-Hickam (JBPH-H). JBPH-H is a joint Navy-Air Force installation located on Oahu, HI. It occupies approximately 27,000 acres, and serves as the headquarters for U.S. Indo-Pacific Command, U.S. Pacific Fleet, U.S. Pacific Air Forces, and Defense Logistics Agency-Indo-Pacific.¹⁴¹ JBPH-H is the homeport for approximately 25 Navy vessels (including ten destroyers and cruisers and thirteen attack submarines); it also hosts the Air Force's 15^th Wing (which includes one C-17 airlift squadron, one C-37 airlift squadron, and one F-22 fighter squadron) and the Hawaii Air National Guard's 154^th Wing (which includes one F-22 fighter squadron, one KC-135 refueling squadron, and one C-17 airlift squadron).¹⁴² Other significant facilities and capabilities at JBPH-H include the Pearl Harbor Naval Shipyard and Intermediate Maintenance Facility (a Navy-owned and operated shipyard that maintains, upgrades, and retires naval vessels), the 613^th Air Operations Center (which provides command and control for Air Force operations throughout the Indo-Pacific region), and the Red Hill Bulk Fuel Facility (a large underground fuel storage facility which DOD is currently defueling in response to the JBPH-H Drinking Water Emergency).¹⁴³

Schofield Barracks. Schofield Barracks is an Army installation located in Honolulu, HI. It occupies approximately 16,000 acres, and is the home of the Army's 25^th Infantry Division.¹⁴⁴

Fort Shafter. Fort Shafter is an Army installation located in Honolulu, HI. It occupies approximately 585 acres, and is the headquarters of U.S. Army Pacific (ARPAC). Other significant units and facilities at Fort Shafter include the U.S. Army Corps of Engineers Pacific Ocean Division, the 94^th Army Air and Missile Defense Command, and the 8^th Theater Sustainment Command.¹⁴⁵

Wheeler Army Airfield. Wheeler Army Airfield is an Army installation located in Honolulu, HI. It occupies approximately 1,400 acres, and hosts the Army Garrison Hawaii headquarters as well as the Hawaii Air National Guard's 298^th Air Defense Group.¹⁴⁶

Pacific Missile Range Facility (PMRF) Barking Sands. PMRF Barking Sands is a Navy installation located approximately five miles outside of Kekaha on the island of Hawaii, HI. It occupies approximately 2,500 acres of land on Hawaii, but the range encompasses over 1,100 square miles of instrumented ocean and 42,000 square miles of controlled airspace. PMRF Barking Sands is the world's largest instrumented sea range, supporting training and RDT&E activities involving surface, undersea, air, and space-based weapons systems.¹⁴⁷

Marine Corps Base Hawaii. Marine Corps Base Hawaii is a Marine Corps installation located approximately 12 miles northeast of downtown Honolulu, HI. It occupies approximately 3,200 acres, and hosts the 3^rd Marine Littoral Regiment, 1^st Battalion 12^th Marines, 3^rd Radio Battalion III MEF, and Marine Aircraft Group 24 (which includes one light attack helicopter squadron, two MV-22 squadrons, and one UAV squadron).¹⁴⁸

Wake Island

Wake Island Airfield. Wake Island Airfield is an Air Force installation located on Wake Atoll (an unincorporated U.S. territory approximately 2,100 nautical miles west of Honolulu, HI). It occupies approximately 2,600 acres and hosts 11^th Air Force, Detachment 1-Pacific Air Forces Regional Support Center. Wake Island Airfield primarily supports trans-pacific military air traffic and missile test activities.¹⁴⁹

Guam and the Northern Mariana Islands

Naval Base Guam. Naval Base Guam is a Navy installation located in Guam. As with other DOD sites in Guam and the Northern Mariana Islands, Naval Base Guam is managed as part of Joint Region Marianas.¹⁵⁰ Naval Base Guam encompasses six noncontiguous sites across the island: Barrigada, North Finegayan, Ordnance Annex, Orote Point, Polaris Point, and Tenjo and Sasa Valley. The installation hosts one submarine squadron (consisting of five Los Angeles-class attack submarines), two submarine tenders, and Navy Expeditionary Forces Command Pacific (CTF-75).¹⁵¹

Marine Corps Base Camp Blaz. Marine Corps Camp Blaz is a Marine Corps installation located in Guam and managed as part of Joint Region Marianas. It is the Marine Corps' newest installation, and will host Marine Corps forces currently stationed at Okinawa beginning in the mid-2020s (expected to include a Marine Expeditionary Brigade (MEB) command element, a Marine Infantry Regiment, a Combat Logistics Battalion, and an Air Combat Element). Camp Blaz currently hosts an Army Terminal High Altitude Area Defense (THAAD) battery.¹⁵²

Andersen Air Force Base. Andersen Air Force Base is an Air Force installation located in Guam and managed as part of Joint Region Marianas. It hosts the 36^th Wing, which supports rotational bomber deployments (B-1 and B-52 aircraft) and regional contingency responses, as well as the Navy's Helicopter Sea Combat Squadron 25 (consisting of MH-60S helicopters).¹⁵³

The Marshall Islands, Micronesia, and Palau

U.S. Army Garrison-Kwajalein Atoll. U.S. Army Garrison-Kwajalein Atoll is an Army installation located on Kwajalein Atoll in the Republic of the Marshall Islands. Its main site occupies approximately 1,360 acres, and hosts the Ronald Reagan Ballistic Missile Defense Test Site, a Major Range and Test Base Facility (MRTBF) supporting RDT&E activities for ballistic missile defense systems, strategic systems, and space tracking systems.¹⁵⁴

Tactical Mobile Over-the-Horizon Radar (Republic of Palau). The Air Force is constructing a site in the Republic of Palau to support the installation of a Tactical Mobile Over-the-Horizon Radar system. Construction should conclude in 2026.¹⁵⁵

Japan (Mainland)

Camp Zama (including Sagami General Depot and Yokohama North Dock). Camp Zama is an Army installation located about 25 miles southwest of Tokyo, Japan. It occupies approximately 578 acres, and serves as the headquarters for U.S. Army Japan, U.S. Army Garrison Japan, I Corps (Forward), and the U.S. Army Corps of Engineers Japan District.¹⁵⁶ It also hosts Army Aviation Battalion Japan (which operates UH-60L helicopters and UC-35 fixed-wing aircraft), the 38^th Air Defense Artillery Brigade, the 35^th Combat Sustainment Support Battalion, the 78^th Signal Battalion, the 311^th Military Intelligence Battalion, the 403^rd Logistics Readiness Center, and the 836^th Transportation Battalion.¹⁵⁷

Shariki and Kyogamisaki Communications Sites. Shariki Communications Site and Kyogamisaki Communications Site are Army installations, located respectively in northern and western Honshu, Japan. Each hosts an Army Navy Transportable Radar Surveillance and Control Model 2 (AN/TPY-2) system, used to detect and track ballistic missile threats to the Indo-Pacific and the continental United States.¹⁵⁸

Fleet Activities Yokosuka. Fleet Activities Yokosuka is a Navy installation located about 43 miles south of Tokyo, Japan. It occupies approximately 568 acres, and hosts a number of surface warships, including a Nimitz-class aircraft carrier (the USS Ronald Reagan, currently the Navy's only forward deployed carrier), a destroyer squadron (consisting of nine Arleigh Burke-class guided-missile destroyers), and three Ticonderoga-class guided missile cruisers.¹⁵⁹ The installation is also home to the U.S. Naval Ship Repair Facility and Japan Regional Maintenance Center.¹⁶⁰

Fleet Activities Sasebo. Fleet Activities Sasebo is a Navy installation located in western Kyushu, Japan. It occupies approximately 150 acres, and hosts a number of surface warships, including an amphibious squadron (consisting of one America-class amphibious assault ship, two San Antonio-class amphibious transport docks, and two Whidbey Island-class dock landing ships) and a mine countermeasure squadron (consisting of four Avenger-class mine countermeasure ships).¹⁶¹

Naval Air Facility Atsugi. Naval Air Facility Atsugi is a joint U.S. Navy-Japan Maritime Self Defense Force installation located about 20 miles southwest of Tokyo, Japan. It occupies approximately 1,234 acres, and serves as a support base for certain Carrier Air Wing Five aircraft (including a helicopter maritime strike squadron and a helicopter sea combat squadron).¹⁶²

Marine Corps Air Station Iwakuni. Marine Corps Air Station Iwakuni is a Marine Corps installation located in southern Honshu, Japan. It occupies approximately 7,100 acres, and hosts two F-35 fighter squadrons and one KC-130 aerial refueling squadron. It also serves as a support base for most Carrier Air Wing 5 aircraft (including four F/A-18 fighter squadrons, one EA-18 electronic attack squadron, and one E-2D command and control squadron).¹⁶³

Yokota Air Base. Yokota Air Base is a joint U.S. Air Force and Japan Air Self-Defense Force installation located in the greater Tokyo metropolitan area, Japan. It occupies approximately 1,750 acres, and serves as the headquarters for U.S. Forces Japan and the Fifth Air Force.¹⁶⁴ Yokota Air Base also hosts the 374^th Airlift Wing, which includes one C-130J squadron and one squadron operating UH-1N helicopters and C-12J aircraft.¹⁶⁵

Misawa Air Base. Misawa Air Base is an Air Force installation located in northern Honshu, Japan. It occupies approximately 3,860 acres, and hosts the 35^th Fighter Wing, which includes two F-16 fighter squadrons.¹⁶⁶

Japan (Okinawa)

Army Garrison Okinawa. Army Garrison Okinawa encompasses a number of noncontiguous Army installations on the island of Okinawa, including Torii Station, Fort Buckner, Tengan Pier, Kuwae Depot Chimuwan, White Beach Fuel Tank Farms, and Naha Military Port. The garrison supports logistical functions (particularly fuel storage and distribution) and can provide regional contingency support.¹⁶⁷

Marine Corps Base Camp Butler. Marine Corps Base (MCB) Camp Butler encompasses contiguous and noncontiguous Marine Corps installations (including Camps Foster, Lester, Courtney, McTureous, Kinser, Hansen, Schwab, and Gonsalves) that together occupy approximately 40,000 acres on the island of Okinawa.¹⁶⁸ MCB Camp Butler hosts the III Marine Expeditionary Force (III MEF), a Marine Air-Ground Task Force and the only permanently forward-deployed Marine Expeditionary Force. Subordinate units of III MEF stationed at MCB Camp Butler include the 3^rd Marine Division, 1^st Marine Aircraft Wing, 3^rd Marine Logistics Group, 3^rd Marine Expeditionary Brigade, 31^st Marine Expeditionary Unit and III MEF Information Group. Other significant facilities and capabilities located at MCB Camp Butler include the Jungle Warfare Training Center and other training areas and live fire ranges.¹⁶⁹

Marine Corps Air Station Futenma. Marine Corps Air Station (MCAS) Futenma is a Marine Corps installation located in southern Okinawa. It occupies approximately 1,200 acres, and hosts two medium tilt-rotary squadrons (operating CH-53E heavy-lift helicopters, AH-1Z Viper attack helicopters, and UH-1Y utility helicopters as well as MV-22 tiltrotor aircraft) and support from Marine Aircraft Group 36.¹⁷⁰

Kadena Air Base. Kadena Air Base is an Air Force installation located near Okinawa City, Okinawa, Japan. It occupies approximately 4,900 acres, and hosts the 18^th Wing, subordinate units of which include a KC-135 refueling squadron, an E-3 AWACS airborne air control squadron, and an HH-60 rescue squadron.¹⁷¹ Until November 2022, Kadena also hosted two F-15D/D fighter squadrons; as of this writing, the Air Force is rotationally deploying F-22 fighter aircraft from Joint Base Elmendorf-Richardson, Alaska.¹⁷²

Republic of Korea

Camp Humphreys. Camp Humphreys is an Army installation located in Pyeongtaek, South Korea (about 40 miles south of Seoul). Camp Humphreys occupies approximately 3,500 acres, and serves as the headquarters for U.S. Forces Korea, the Eighth Army, and U.S. Marine Corps Forces Korea. ¹⁷³ Camp Humphreys also hosts the 2^nd Infantry Division/Republic of Korea-U.S. Combined Division, the Army's only permanently forward-stationed division (major units include a rotational armored brigade combat team, two field artillery brigades, and a combat aviation brigade).¹⁷⁴

U.S. Army Garrison Daegu (Camps Henry, Walker, George and Carroll; Busan Pier 8). U.S. Army Garrison Daegu encompasses five significant Army installations in eastern South Korea: Camps Henry, Walker, and George (located in the Daegu metropolitan area); Camp Carroll (located in North Gyeongsan province); and Busan Pier 8 (located in the Busan metropolitan area). Significant units and capabilities include the 19^th Sustainment Command (Expeditionary), the 403^rd Army Field Support Brigade-Korea, and Material Supply Center-Korea.¹⁷⁵

U.S. Army Garrison Yongsan-Casey (K-16, Yongsan Garrison, and Camp Casey). U.S. Army Garrison Yongsan-Casey encompasses installations in the Seoul metropolitan area of South Korea: the K-16 airfield, Yongsan Garrison, and Camp Casey. In accordance with the terms of two bilateral agreements, DOD is gradually returning these sites to the South Korean government, with many former functions and units moving to Camp Humphreys.¹⁷⁶

Fleet Activities Chinhae. Fleet Activities Chinhae is a Navy installation in Changwon City, South Korea. The only Navy installation in Korea, Fleet Activities Chinhae hosts U.S. Naval Forces, Detachment Chinhae, a small detachment of approximately 300 sailors which coordinates operations, exercises, and other institutional cooperation between the U.S. and ROK Navies.¹⁷⁷

Marine Corps Installation Camp Mujuk. Marine Corps Installation Camp Mujuk is a Marine Corps installation located in Pohang, South Korea. The only Marine Corps installation in Korea, Camp Mujuk supports rotational Marine Corps units and combined U.S.-ROK training exercises.¹⁷⁸

Osan Air Base. Osan Air Base is an Air Force installation located about 20 miles south of Seoul, South Korea. It occupies approximately 1,500 acres, and serves as the headquarters of the Seventh Air Force. Osan Air Base also hosts the 51^st Fighter Wing (which includes one A-10 attack squadron and one F-16 fighter squadron) and one U-2 reconnaissance squadron from the 9^th Reconnaissance Wing.¹⁷⁹

Kunsan Air Base. Kunsan Air Base is an Air Force installation located about 7 miles west of Gunsan City. It occupies approximately 2,549 acres, and hosts the 8^th Fighter Wing (which includes two F-16 fighter squadrons).¹⁸⁰

The Philippines

Nine Enhanced Defense Cooperation Agreement (EDCA) Sites. Under the Enhanced Defense Cooperation Agreement, the U.S. military has rotational access to nine defense sites across the Philippines. Five of these installations were agreed upon in 2014 (Antonio Bautista Air Base in Palawan, Basa Air Base in Pampanga, Fort Magsaysay in Nueva Ecija, Lumbia Airport in Cagayan de Oro, Benito Ebuen Air Base in Cebu), while the remaining four were agreed upon in 2023 (Naval Base Camilo Osias in Sta Ana, Cagayan; Lal-lo Airport in Lal-lo, Cagayan; Camp Melchor Dela Cruz in Gamu, Isabela and Balabac Island in Palawan).¹⁸¹

Singapore

Navy Region Center Singapore. The U.S. Navy maintains a presence in Singapore primarily to manage and provide logistical support for visiting surface warships (mainly at Changi Naval Base and Sembawang shipyard). In addition, Paya Lebar Air Base hosts rotational Air Force personnel and aircraft. Other DOD activities present in Singapore and managed through Navy Region Center Singapore include Logistics Group Western Pacific, Naval Supply Systems Command Fleet Logistics Center Yokosuka Site Singapore, Military Sealift Command Far East, and Defense Contract Management Agency Singapore.¹⁸²

Australia

Royal Australian Air Force (RAAF) Base Darwin and Robertson Barracks. RAAF Base Darwin and Robertson Barracks are two Australian military installations located in the Northern Territory. Since 2011, they have hosted a rotational U.S. Marine Air Ground Task Force known as Marine Rotational Force-Darwin (MRF-D). MRF-D rotations are typically six months and involve combined exercises and training with the Australian military and other regional partners.¹⁸³

RAAF Base Tindal. RAAF Base Tindal is an RAAF installation in Australia's Northern Territory that hosts rotational deployments of U.S. aircraft and personnel and supports the Enhanced Air Cooperation (EAC) initiative between the RAAF and U.S. Air Force. To support its usage of the base (which includes the rotational deployment of B-52 bomber aircraft), the United States is currently funding construction of a new bulk fuel facility.¹⁸⁴

Naval Communication Station Harold E. Holt. Naval Communication Station Harold E. Holt is a naval installation jointly operated by the Royal Australian Navy (RAN) and the U.S. Navy. The site occupies approximately 5,100 acres, and broadcasts communications to Australian and U.S. submarines using Very Low Frequency (VLF) communications.¹⁸⁵

Other Sites. As part of the Australia-United Kingdom-U.S. (AUKUS) pact, the Royal Australian Navy's (RAN) HMAS Stirling naval base (located in Perth, Western Australia) will host rotational deployments of U.S. and U.K. nuclear-powered submarines beginning in 2027. U.S. submarines will also increase the frequency of visits to HMAS Stirling beginning in 2023.¹⁸⁶

British Indian Ocean Territory (Diego Garcia)

Naval Support Facility Diego Garcia. Naval Support Facility Diego Garcia is a Navy installation located on Diego Garcia, an atoll in the British Indian Ocean Territory. It occupies approximately 6,200 acres, and its primary function is to provide logistical support for forces operating in and around the Persian Gulf and Indian Ocean. Significant units and capabilities based at Diego Garcia include a maritime pre-positioning squadron and 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 (providing space domain awareness and satellite control, respectively).¹⁸⁷

Appendix B. Historical Overview of Indo-Pacific Defense Infrastructure

U.S. defense infrastructure in what is now termed the Indo-Pacific region dates to the early 19^th century. Although only in use for four months, Fort Clatsop, the winter encampment established by the U.S. Army's Corps of Discovery in 1805, was the first U.S. defense facility on North America's Pacific coast.¹⁸⁸ As U.S. expansion and settlement accelerated, the Army established a number of permanent outposts in what are now the states of Oregon, Washington, and California beginning in the 1840s and 1850s.¹⁸⁹ The U.S. Navy also began to operate in the Pacific during this period, although the lack of development in coastal areas (particularly prior to the 1848 acquisition of California) meant that American vessels relied mainly on foreign ports for provisioning and repair.¹⁹⁰

Between the end of the Mexican-American War (1848) and the Spanish-American War (1898), the U.S. purchased Alaska (1867) and took possession of Midway Atoll (1867).¹⁹¹ In 1898, expansionist sentiment and victory over Spain led to the U.S. annexation of the Republic of Hawaii and the formerly Spanish territories of the Philippines and Guam. From an infrastructure perspective, each of these areas quickly acquired significance. A major rationale for the annexation of Hawaii was its importance as a refueling and supply stop for vessels transiting the Pacific, and in 1899 the Navy established a naval station at Pearl Harbor.¹⁹² In the Philippines, the U.S. military built or expanded a wide array of installations, including a naval base and coastal fortifications at Subic Bay and a number of Army outposts throughout the territory.¹⁹³ In Guam, the Department of the Navy established a naval station and a Marine barracks.¹⁹⁴

Given the centrality of the European theater to World War I (1914-18), the role played by U.S. Indo-Pacific defense infrastructure was minimal.¹⁹⁵ However, many of the war's military innovations and geopolitical consequences influenced regional infrastructure developments in the 1920s and 30s.¹⁹⁶ For U.S. planners, Pacific defense sites during the interwar period played two major roles: they enabled the Navy to operate in the region; and they offered a degree of protection to U.S. territories and commercial interests. As conflict with Japan became more plausible in the late 1930s and early 1940s, the U.S. military increased the resources and attention devoted to Pacific defense infrastructure, constructing new air and naval facilities at Midway Atoll and Wake Island.¹⁹⁷

Japan's surprise attacks on the United States in December 1941 targeted Pearl Harbor as well as other key regional defense sites, including bases on the Philippines and Wake Island. Allied prosecution of the ensuing Pacific War relied heavily on both the existing infrastructure and significant new construction. Military bases, training areas, depots, arsenals, and port facilities along the West Coast and in Hawaii played important roles in staging and sustaining the projection of U.S. military forces westward into the Pacific. Dozens of West Coast shipyards—primarily located in the Puget Sound, Portland, San Francisco Bay, and Los Angeles areas—built warships and cargo vessels for the U.S. Navy and merchant marine, and Southern California became one of the country's major centers of aircraft manufacturing.¹⁹⁸ In the Pacific theater itself, military engineers—particularly naval construction battalions (known as 'Seabees')—made possible operations in remote and austere environments by building dozens of advance bases to support naval vessels, aircraft, and ground forces.¹⁹⁹

By 1945, the United States oversaw a vast infrastructure network spanning from the West Coast to mainland Asia. In the immediate aftermath of World War II, the U.S. military requisitioned and built installations in Japan (and its former territories in Korea and Micronesia) to support postwar occupation and reconstruction activities.²⁰⁰ As tensions with the Soviet Union intensified, U.S. planners shifted their focus, reorienting America's regional basing posture around deterring communist attacks on U.S.-aligned governments, enabling the rapid buildup and supply of forces in the event of a crisis, and signaling to both allies and potential adversaries that the United States was committed to the region.

Beginning with the Truman Administration, the geographical anchor of America's Pacific strategy was held to be a "defensive perimeter" running from the Aleutians through Japan, the Ryukyu Islands (Okinawa), and the Philippines.²⁰¹ The outbreak of the Korean War in 1950 led to the explicit inclusion of South Korea within this perimeter. The U.S. war effort itself relied heavily on logistical support from existing and newly developed defense sites—particularly logistical hubs in Japan.²⁰² By the mid-1950s, DOD's infrastructure footprint in Northeast Asia had expanded to encompass dozens of major installations in South Korea, mainland Japan, and Okinawa.

Elsewhere in the Indo-Pacific, the United States maintained large bases in the Philippines (which gained independence in 1946, but continued to allow U.S. basing), Guam, and Hawaii. This basing posture was informed by what became known as the 'island chain strategy,' a framework for containing communist expansion by "mak[ing] safe the offshore island chain which swings south through Japan, the Ryukyus, the Philippines, Australia and New Zealand" (in addition to this 'First Island Chain,' later strategists would refer to a 'Second Island Chain' stretching from Japan to the Marianas and Palau, as well as a 'Third Island Chain' centered on the Hawaiian Islands).²⁰³

Beginning in the early 1960s, escalating U.S. involvement in the Vietnam War began to place new and increased demands on Pacific defense sites. By 1969, the United States had built a large defense infrastructure network in South Vietnam, encompassing 26 "major base camps" spread throughout the country.²⁰⁴ Installations outside South Vietnam also supported U.S. combat operations—hundreds of thousands of personnel and millions of tons of materiel passed through mainland Japan or Okinawa on their way to Vietnam, for instance, while bases in the Philippines provided logistical support and staging for aircraft and troops.²⁰⁵

With the end of the Vietnam War, the onset of U.S.-Soviet detente, and the opening of relations between the U.S. and the PRC, the strategic importance of Pacific defense infrastructure appeared to diminish.²⁰⁶ In the late 1970s, the United States ended its military presence in Taiwan pursuant to commitments made as part of the normalization of U.S.-PRC ties, and the Carter Administration unsuccessfully sought to withdraw all U.S. ground forces from South Korea.²⁰⁷ Strategic thinking around regional defense infrastructure shifted again in the early 1980s, when the Reagan Administration adopted a global posture that placed more emphasis on regional forward presence and initiated a major military buildup.²⁰⁸

The end of the Cold War brought another reassessment of the U.S. defense role in the Indo-Pacific. In its 1990 and 1992 Pacific strategies, DOD outlined a vision of successive regional force and infrastructure reductions in response to the changed geopolitical environment.²⁰⁹ In 1991, a combination of natural disaster and diplomatic impasse led the U.S. to evacuate its Philippine bases and end almost a century of military presence in the country. In 1995, however, the U.S. Security Strategy for the East Asia-Pacific (sometimes referred to as the Nye Report) avoided further reductions, instead committing the military to "maintain a stable forward presence in the region, at the existing level of about 100,000 troops, for the foreseeable future."²¹⁰ Further adjustments to U.S. basing posture occurred in South Korea, where the U.S. and Republic of Korea (ROK) governments in 2004 agreed to consolidate U.S. forces in installations centered on two regional "hub" areas south of Seoul.²¹¹

U.S. security strategy in the Indo-Pacific during the 1990s and early 2000s focused on managing sources of regional instability, especially tensions between North and South Korea and between the PRC and Taiwan. After the commencement of the Global War on Terror (GWOT) in 2001, Indo-Pacific locations like Diego Garcia also provided significant logistical support for combat operations in the greater Middle East, especially following the 2003 invasion of Iraq.²¹² Defense infrastructure also supported humanitarian operations in the aftermath of natural disasters, including the 2004 Indian Ocean tsunami and the 2011 earthquake, tsunami, and nuclear disaster in Japan.²¹³

Under President Barack Obama, the U.S. military began to shift its focus from GWOT operations to great power competition with the PRC. In 2011, the Obama Administration announced a "pivot to Asia" to bolster and expand the U.S. role in the region. To that end, DOD shifted more forces (especially naval) to the Indo-Pacific and negotiated rotational access to additional military bases in countries like Australia and the Philippines.²¹⁴ The focus on strategic competition with China expanded under the Trump Administration, which prioritized infrastructure investments in locations such as Guam and Micronesia while also seeking larger contributions from Indo-Pacific allies to support U.S. basing costs.²¹⁵ In 2020, Congress established the Pacific Deterrence Initiative, a set of regionally focused defense investments that includes infrastructure as a major activity category (Section 1251 of the William M. (Mac) Thornberry National Defense Authorization Act for Fiscal Year 2021, P.L. 116-283).