South Korean Political Crisis: Martial Law and Impeachment

In December 2024, South Korea plunged into a political crisis that could have significant implications for U.S. interests, including U.S. policies toward North Korea, China, Japan, and Russia. At around 10:25 p.m. on December 3, after months of escalating tension and political gridlock between the executive and the opposition-controlled National Assembly (Figure 1), President Yoon Suk-Yeol declared martial law "to protect the constitutional order" from the left-of-center opposition party, the Democratic Party (DP), and its allies. Yoon has described these opposition parties as pro-North Korean "anti-state forces." Yoon dispatched military and police forces to the National Assembly complex to prevent it from convening and reportedly to arrest party leaders. Most legislators—some of whom came of age protesting against South Korea's military government in the 1970s and 1980s—managed to evade or break through the security cordon.

Figure 1. Party Strength in the National Assembly

Source: Republic of Korea National Assembly.

At 1:00 a.m. on December 4, the National Assembly voted 190-0 to demand Yoon rescind his order. (The National Assembly can override a martial law decree.) Shortly before 4:30 a.m., Yoon lifted martial law. (Table 1.)

Later on December 4, opposition parties jointly filed a motion of impeachment against Yoon and key members of his government. A December 7 vote narrowly failed, with almost all of Yoon's People Power Party (PPP) representatives boycotting the proceedings. A second vote on December 14 succeeded, with 12 PPP representatives voting in favor. Factors influencing PPP members' shift appear to have been Yoon's public defiance and polls indicating Yoon's approval ratings—which had been in the 20%-30% range for most of his tenure—had dipped below the teens. Over 70% of Koreans polled supported impeachment, and tens of thousands of protestors, as well as many civil society groups, mobilized in support of impeachment. Following his impeachment, Yoon was suspended from office and Prime Minister Han Duk-soo became Acting President. On December 27, however, following disagreements with Han, the National Assembly impeached him. Finance Minister Choi Sang-mok became Acting President.

Next Steps

Yoon's impeachment goes to South Korea's Constitutional Court for a trial, which must be decided within 180 days. If the court upholds the impeachment, as it did with President Park Geun-hye in 2017, Yoon would be ousted from office and elections must be held within 60 days. If the court overturns the impeachment, as it did with President Roh Moo-hyun in 2004, Yoon would be reinstated and the next presidential election would be slated for its regularly scheduled date in March 2027. (By law, South Korean presidents serve one five-year term.) Park's and Roh's verdicts were returned within 63 days and 92 days, respectively. Separately, Yoon is under criminal investigation for insurrection, a charge that supersedes the president's usual immunity from prosecution.

The timing of the court's verdict could be important because the presumed front-runner for an early election, DP leader Lee Jae-myung, faces multiple court proceedings in which guilty verdicts could render him ineligible for political office. Lee, who lost the 2022 presidential election to Yoon by 0.7% of the vote, is accused of corruption, violating election laws, and involvement in an illegal cash transfer to North Korea. He is appealing a November 2024 election law conviction that bars him from running for office.

U.S. Government Response

As shown in Table 1, during the six hours martial law was in place and in the aftermath of its lifting, Biden Administration officials expressed "concern" at Yoon's martial law declaration. They also stated their expectation that political disputes would be resolved peacefully and lawfully, sentiments some Members of Congress echoed. Some Members criticized Yoon's martial law declaration directly. Following Yoon's impeachment, President Joe Biden spoke with then-Acting President Han to express "his appreciation for the resiliency of democracy and the rule of law" in South Korea.

Geostrategic Implications

Since assuming office in 2022, Yoon has brought South Korea into closer alignment with the United States on North Korea, China, Japan, and Ukraine. The DP, whose approval rating now tops the PPP's by double-digits in some polls, tends to advocate starkly different policies. The Assembly's first impeachment motion, for instance, accused Yoon of "neglect[ing]" geopolitical balance by "antagonizing" North Korea, China, and Russia and by pursuing a "strange Japan-centered" foreign policy. DP Leader Lee reportedly said including those items had been a mistake, and they were not included in the second impeachment motion.

A question facing U.S. policymakers and Congress is whether Yoon's deployment of the Republic of Korea (ROK, or South Korea) military to implement martial law, without notifying U.S. military commanders in Korea, poses concerns about the state of alliance coordination. Additionally, the fallout from Yoon's moves may have compromised the PPP government's ability to engage in major foreign policy initiatives. Under an interim president, Seoul may be at a disadvantage in advocating for its positions if the next U.S. Administration pursues changes affecting U.S.-ROK relations, including on tariffs, the size of U.S. troop deployments to South Korea, policy toward semiconductors and other technology sectors, and/or modifying or withdrawing from the U.S.-ROK burden-sharing agreement that was finalized in November 2024.

Similarly, Yoon's suspension and possible removal from office raise questions about the continuation of several foreign policies he has pursued, including:

• A relative hardline policy toward North Korea that treats North Korea as an existential threat and emphasizes deterrence. In contrast, South Korean progressives tend to emphasize engagement policies.
• Integrating South Korea into the U.S.-led network of alliances and partnerships in the Indo-Pacific, with a goal of making South Korea a "global pivotal state," including by championing democratic values. Many South Korean progressives have criticized Yoon's policy.
• A greater willingness than prior ROK leaders to publicly criticize China's actions. DP Leader Lee has questioned this approach.
• Improving relations with Japan and expanding ROK-U.S.-Japan relations, which have been centerpieces of Yoon's foreign policy, an approach involving compromises on historical issues with Japan that Lee has characterized as "shameful."