Strong ties, high anxiety: The US-Korean alliance ahead of the 2024 election

On the eve of a presidential election that could decide the fate of the U.S. alliance system, America’s security partnership with the Republic of Korea (ROK) has never been stronger and more able to deter North Korea or, failing that, to defeat aggression.

South Korea is a key pillar of the U.S. alliance network in the Indo-Pacific region, a long-standing and trusted ally, and a beacon of democracy, freedom, and economic growth. South Korea’s rise to success was in no small measure due to America’s investment of blood and treasure, for which the Korean people remain deeply grateful. Today, the alliance deters North Korea and provides cost-free facilities that facilitate U.S. regional military operations and allow the United States to send an important message of deterrence to China, Russia, and other potential adversaries.

However, North Korea’s nuclear capabilities, a dangerous North Korea-Russia “comprehensive strategic partnership,” and a U.S. presidential candidate who has questioned the value of the U.S.-Korea military partnership have shaken South Korea’s confidence in the future of the alliance. In many Koreans’ eyes, both the fate of the alliance and Korea’s security are at stake in this U.S. presidential election.

Stronger than ever

America’s alliance with South Korea is more capable and interoperable than ever. U.S. and ROK alliance managers have never been more in sync, including in their assessments of the North Korean threat and their concern about China’s ambitions, Russia’s aggression against Ukraine, Moscow’s new military ties with North Korea, and the Russia-China “partnership without limits.”

ROK President Yoon Suk Yeol has moved Korea closer to the United States while holding China at arm’s length. Yoon has responded positively to Washington’s urging to work more cooperatively with Japan—America’s other key East Asian ally. Yoon and Japanese Prime Minister Fumio Kishida have deftly managed Korea-Japan differences and forged a solid bilateral relationship. Today, South Korea, Japan, and the United States have built an important trilateral partnership, including on security issues, fulfilling a long-standing U.S. goal. Nevertheless, progress in stabilizing South Korea-Japan ties remains fragile, and shifts in domestic political winds or leadership in either Seoul or Tokyo could result in new or revived tensions.

Yoon has adopted a firm posture toward North Korea—reversing his progressive predecessor’s conciliatory approach that had frequently raised concerns in Washington. In contrast to the previous Moon Jae-in government’s concessionary approach, Yoon’s administration has emphasized military strength, deterrence, and assured retaliation in dealing with North Korea.

North Korea, Russia, Ukraine, NATO, and new horizons

The Yoon government has reacted strongly to Russian President Vladimir Putin’s June 2024 summit with North Korean leader Kim Jong Un and the conclusion of a new Russia-North Korea treaty that includes a mutual assistance clause. Seoul has even hinted that it might begin direct military assistance to Ukraine if Russia provides sensitive military and satellite technology to North Korea.

South Korea is building closer ties with NATO and expanding its sale of arms to European countries. Seoul has actively participated in recent NATO summits as a member of the “Indo-Pacific 4” (together with Japan, Australia, and New Zealand), including the July 2024 75th-anniversary summit in Washington.

South Korea is a core part of the liberal international order and a pillar of democracy, freedom, and free-market economic growth. And Yoon has left no doubt that he sees the alliance with the United States, and the U.S. extended deterrent, as more central than ever to his country’s security.

Restoration and reaffirmation

Over the past three years, the Biden administration has restored bilateral goodwill and Korean confidence in the U.S. defense commitment, which were damaged by former President Donald Trump’s blunt criticism of Korea, his questioning of the value of the alliance, and his demand for an unprecedented increase in South Korean defense burden sharing.

During the Trump administration, South Koreans were dismayed by charges they were not contributing enough to their defense and to the upkeep of U.S. forces, despite providing the bulk of front-line combat forces against North Korea, funding almost the entire cost of the construction of the United States’ largest overseas military base, and despite Seoul’s record of agreeing to regular biennial increases in support for U.S. forces.

Under the Biden administration, the United States has resumed large-scale military exercises with South Korean forces, which Trump unilaterally suspended as part of his failed diplomacy with North Korea. The absence of those exercises led, in the view of experts, to a decline in military readiness. The United States has also regularized the dispatch of strategic military assets, including nuclear-capable bombers, aircraft carriers, and attack submarines, to Korea to demonstrate its preparedness to use all the weapons in its arsenal to defend its ally.

The Washington Declaration, issued at the April 2023 U.S.-ROK summit between Presidents Joe Biden and Yoon, contained the strongest-ever U.S. extended deterrence commitment to South Korea. It also established the Nuclear Consultative Group to discuss, plan, and coordinate the possible use of U.S. strategic and tactical nuclear weapons. The Washington Declaration eased but did not eliminate South Korean concerns that a more inwardly focused United States might not stand by its commitment to defend South Korea in a crisis, including with nuclear weapons. For that reason, many in South Korea continue to want even more concrete extended nuclear deterrence assurances than those already provided by Washington.

High anxiety

Despite a reinvigorated bilateral alliance and strong U.S. assurances, South Korea remains anxious about the alliance’s future. Concerns that Pyongyang’s nuclear arsenal is now a permanent threat, and that the Russia-North Korea partnership has created a serious new threat, are contributing to this anxiety.

But the main factor troubling South Koreans is the belief that Trump’s return to the White House would end the Biden administration’s alliance-strengthening approach, bring renewed anti-alliance rhetoric and massive burden-sharing demands, and even see a reduction in U.S. forces on the Korean Peninsula. Such concerns have fueled a lively debate in South Korea about the need to acquire its own nuclear weapons—a debate that has been spurred by former Trump administration officials who have proposed downsizing the U.S. military presence and shifting the U.S. military’s mission away from the defense of Korea.

As a result, the Biden administration has further strengthened the U.S. commitment, including with an agreement to regularize the deployment of U.S. strategic assets to Korea. This new agreement should ease ROK concerns, but we should not underestimate the strength of pro-nuclear sentiment in South Korea, especially if Washington decides to distance itself from its longtime ally.

Recommendations

The next U.S. president should build on the strong foundation that has been laid for future U.S.-Korea cooperation. The new president will find a willing partner in Seoul for a more comprehensive partnership, including on security issues, economic and technology cooperation, climate change, supply chain stability, peacekeeping, and humanitarian and development assistance. Taking advantage of this opportunity would enhance America’s own security and stature.

Dealing with the North Korean nuclear and conventional threats, however, must remain the alliance’s central priority. Unilateral U.S. steps to deal with Pyongyang must be avoided, particularly actions that might be perceived in Seoul as signaling acceptance of North Korea’s nuclear arsenal.

America’s allies and partners around the globe will watch carefully how the next U.S. administration manages ties with Seoul. The next U.S. president will have an opportunity to send a message about the importance of alliances and the value of America’s word and commitments. Failure to convey that message would have enormous consequences for America’s credibility and leadership.

But if a Trump victory over Democratic nominee Kamala Harris in November brings renewed questioning of the alliance and attacks on Seoul’s defense contributions, officials in the next administration will need to make the strongest possible case for alliance ties with Seoul and why they are in America’s interest. Congressional supporters of the bilateral alliance, particularly Republicans, will play a major role in this regard.

Lastly, South Korea’s president and senior Korean officials will have to engage in unprecedented outreach to the Trump team to make the case for the alliance and continued U.S. support. They should not assume that their arguments will be accepted. And if Trump translates his anti-alliance views and long-standing animus toward South Korea into policy, it will require a special level of courage by U.S. officials to push back against a man who appears to value personal fealty more importantly than loyalty to the alliance-related principles, ideas, and relationships that previous presidents have always treasured.