What If the U.S.-Korea Alliance Ended?

We tend to view the world as static until events such as the recent standoff between South Korea and Japan shock us into the realization that what we took for granted may not in fact be permanent.

Seoul’s decision to withdraw from the General Security of Military Information Agreement (GSOMIA), its intelligence sharing agreement with Japan, has led some to raise concerns about the future of the U.S.-Korea alliance. It has been suggested that we are seeing the withering of the alliance, or that South Korea is distancing itself from the United States. Long-time Korea expert Evans Revere has even said that when the history of the end of the U.S. security position in Northeast Asia is written it will begin with GSOMIA.

The decision on GSOMIA did not occur in a vacuum and the alliance has been under stress from growing historical and economic tensions between Seoul and Tokyo, as well as U.S. pressures on the alliance to maximize its own short-term interests.

Despite these stresses it is premature to think that the alliance could end in the near-term, not while the alliance has strong support in both the United States and South Korea. According to a recent poll by the Chicago Council on Global Affairs, 69 percent of Americans support maintaining U.S. troops in South Korea, while a poll earlier this year by the Asan Institute for Policy Studies found that a majority of South Koreans have a favorable view of U.S. forces in South Korea and 67.7 percent support U.S. troops remaining in South Korea in the future.

However, the current tensions should also serve as a reminder to Washington, Tokyo, and Seoul of the challenges they would face if the alliance were to end and how their ability to meet those challenges would be circumscribed.

In the absence of the U.S. security presence, South Korea would face an immediate dilemma in how best to provide for its national security. Seoul would be confronted with a nuclear-armed North Korea without the security of the U.S. nuclear umbrella to deter North Korea from using its nuclear capabilities to blackmail concessions from South Korea or the capabilities of the United States’ conventional forces in the event of a conflict.

Managing this challenge would force the South Korean government to consider what options it had for maintaining an independent defense posture or forming new alliance arrangements, as well as how it might need to reshape its relationship with North Korea.

If Seoul sought to maintain an independent defense posture without forming new alliances to balance North Korea, it might seriously have to consider developing an independent nuclear deterrent. Some conservative politicians have been calling for South Korea to develop its own nuclear weapon for years. The idea has support in South Korea. A 2017 Gallup Korea poll found that 60 percent of South Koreans believed it should have its own nuclear deterrent. In the absence of the U.S.-Korea alliance support for a South Korean nuclear weapon could grow, but it would most likely come with economic costs. The South Korean economy is dependent upon trade, and it could face significant economic sanctions to pressure it to pull back from an effort to develop a nuclear weapon and could see its access to fuel for its nuclear power plants cut off by the Nuclear Suppliers Group.

In the absence of an alliance with the United States it is unclear that South Korea would have attractive alliance partners with which to replace the United States. Among democratic states in the region, India and Australia are too distant and currently incapable of providing a military counterweight to North Korea. While Japan might seem a natural partner, current relations would seem to preclude that possibility. Additionally, in the absence of the U.S. also withdrawing from Japan, deeper ties with Tokyo would not seem to be an option.

That would leave South Korea with the options of aligning with China or seeking a deeper relationship with North Korea. While deeper ties with Beijing may be appealing in terms of assistance in dealing with Pyongyang, Seoul would likely be required to align its foreign policy with Beijing and might face other costs, including accepting terms for reunification with North Korea that encroach on South Korean autonomy. Whether in an alliance with Beijing or seeking to maintain an independent foreign policy, South Korea would further expose itself to the type of coercion that China used when the THAAD missile defense system was deployed with little to lean on to counter Chinese pressure.

If Seoul were to try and settle its differences with Pyongyang to reduce the threat it faces the idea of a Korean confederation might be revived. Under this model there would be one Korean country with a unified foreign policy, but each state managing its own domestic affairs. While this might create the possibility of reducing tensions with North Korea, South Korea would have no assurances that Pyongyang would not at some point in the future seek to coerce it in the absence of ties to other security partners.

Beyond the larger strategic questions, there would also be practical costs for South Korea. It would likely lose access to intelligence, reconnaissance, and surveillance capabilities that it now depends on the United States to provide. While South Korea is working to improve its capabilities in these areas to prepare for Op-Con transfer, it would still be at a deficit without access to U.S. capabilities.

While South Korea might face the most complex set of challenges from the end of the alliance, Japan and the United States would also face challenges.

Whatever Japan’s current concerns about Seoul’s constant push for it to atone for its actions during the colonial period and World War II, there would be little left to constrain South Korea from pushing Japan on these issues if its alliance with the United States came to an end. Depending on South Korea’s strategic choices, it could face the development of a loosely united anti-Japan front consisting of China and the two Koreas.

The loss of Seoul as a security partner in the region would weaken Japan’s own security position even without countries aligning against Japan. Beijing would see its space to operate expand as U.S. troops move further from its boarder. As China continued to rise, the loss of South Korea as a partner could potentially place Japan under pressure in time to reach its own accommodation with China.

Having Seoul as an economic and security partner, even if history makes a more formal alliance less possible, places Japan in a stronger position to balance China in the future with the United States than if South Korea’s alliance with the United States ended.

However, should the alliance end, Tokyo would have a strong interest in seeing South Korea maintain an independent foreign policy rather than become a formal ally of China. In a future conflict there would remain the possibility of Seoul joining Washington and Tokyo in efforts to balance Beijing.

This could create difficult choices for Tokyo. If Seoul were to pursue an independent foreign policy, it would likely need a nuclear deterrent, but given the history between South Korea and Japan seeing two states on the Korea peninsula with nuclear weapons would be an unappealing option. It also means Tokyo may have to push internationally for support for a South Korean nuclear option as an economically weakened Seoul would be a less formidable future balancing partner and more likely to accept Chinese aid to relieve its economic woes.

It could also raise the question of whether Japan needs to develop its own nuclear deterrent.

For the United States, ending the alliance with South Korea and withdrawing troops from the Korean peninsula would leave it facing the same strategic question as Japan: What is the best possible security arrangement on the Korean peninsula in the absence of the alliance?

Similar to Japan, the United States would face the difficult question of whether to acquiesce in South Korea gaining an independent nuclear deterrent. While the United States presumably would not face the same historical anxieties that Japan would from a South Korean nuclear weapon, it would have concerns about additional nuclear proliferation. Allowing South Korea to have a nuclear deterrent would make it more difficult to prevent other countries from going nuclear, including Japan. It would also complicate U.S. efforts to balance China in the region. At a minimum, the end of the alliance would complicate efforts to denuclearize North Korea.

There would be other, more practical costs for the United States as well. With the end of the alliance in South Korea, it would need to either decommission the troops that are currently stationed in South Korea or build new facilities to house them in the United States. If it chose to station them in the United States, it would increase the cost of maintaining those troops without the access to South Korean facilities and burden sharing.

In economic terms there would likely be increasing cooperation between South Korean and Chinese tech firms, diminishing the advantages that U.S. alliance system currently enjoys in technology. The United States might also lose a valuable partner in international organizations on economic issues, including in areas such as setting standards for new technologies.

In the absence of the U.S.-Korea alliance, the United States would need to buttress the U.S.-Japan alliance. If that alliance were to end as well, it would make the U.S. presence in East Asia as a security partner untenable and also allow China to break out of the first island chain around the Asian mainland. The United States would be unable to afford for the end of the U.S.-Korea alliance to destabilize the U.S.-Japan alliance.

While it is unlikely that the alliance will end in the near future or even in the medium-term, it is useful to consider what ending the alliance would mean for the United States, South Korea, and Japan in the current environment. Many of the challenges laid out here might be mitigated if the alliance were to end on relatively amicable terms, or be made more challenging if it would to end in a contentious fashion.

In short, without their alliance, the United States, Japan, and South Korea would all find it more challenging to deal with China and North Korea, while having fewer resources to address those challenges.

While relations between all three countries are at a low point, without each other the United States, South Korea, and Japan would find themselves in a strategically more challenging position with little benefit from ending their ties. That might be good to keep in mind at times like these.