Like It or Not, the South Korea-US Alliance Is Changing

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Like It or Not, the South Korea-US Alliance Is Changing

The ROK-U.S. alliance is at a time of transition, and a lot of changes will be required to maintain the strength and effectiveness of the alliance into the future.

Like It or Not, the South Korea-US Alliance Is Changing

U.S. INDOPACOM Commander Admiral John Aquilino visits South Korea, June 3, 2021.

Credit: U.S. Army photo by Staff Sgt. Kris Bonet

Early next year, the next president of South Korea will be sworn in. The new president – whoever that will be – will face some major foreign policy and security issues, but the potential candidates have so far been focused mostly on domestic matters.

This election cycle, North Korea is causing less difficulty than usual, with the Kim Jong Un regime having been greatly affected by weather-related natural disasters and also by COVID-19. Instead, the most important foreign policy and security issues are clearly concerned with the United States and China.

There are deep diplomatic differences between President Joe Biden of the United States and President Moon Jae-in of South Korea. Biden wants Moon to abandon his peace-oriented policy toward North Korea, but Moon insists on continuing to try, despite the underwhelming results so far achieved. Can the next president of South Korea make any better progress?

Another point of contention between Seoul and Washington is Biden’s desire for the South Korean military to take a more active role in the wider region, in particular by participating in various U.S.-led multilateral military exercises. The incoming South Korean president will need to finesse this issue carefully if relations with China are to remain cordial.

Can the next president of South Korea initiate any new policies toward the United States, China, and North Korea? The truth is that South Korea’s policies toward these countries are interdependent in many different ways. If there are any solutions to be found for this Gordian Knot, then the ROK-U.S. alliance is the best hope we have. So how should we envisage the future of the long-standing alliance between the ROK and the United States?

Moon’s Promises to China: The Three Noes

When the Terminal High Altitude Area Defense (THAAD) missile defense system was deployed on South Korean soil, China objected vigorously and used its commercial leverage to punish South Korea. As a consequence, Moon was obliged to placate China by making three promises. Will these “three noes” cause difficulties for the next president?

The first promise was that the United States will not deploy additional THAAD systems in South Korea. The U.S. budget for fiscal year 2021 has no funding for additional THAAD systems, but there are some funds allocated for upgrading the existing one to integrate it into a remote networked command and control system, together with Patriot and other systems deployed near the Korean Peninsula. This is a third and final phase based on the U.S. adoption of the Joint All Domain Command and Control system which U.S. Forces Korea (USFK) plans to adopt shortly.

The second “no” is that trilateral security cooperation between the U.S., Japan, and South Korea will not develop into a military alliance. Given the dire state of relations with Japan, this promise is easy to keep for any South Korean president.

The third promise is that South Korea will not participate in the U.S. Missile Defense Agency’s (MDA) regional missile defense system. In practice the THAAD system deployed at Seongju has already been integrated into the MDA’s regional architecture. Staff at the South Korean Ministry of National Defense (MND) have implicitly acknowledged the fact. As for any further cooperation with the MDA, the MND has made clear that it prefers to develop its own missile defense system.

It seems, then, that Moon’s “three noes” will not seriously constrain the next president.

Hypersonic Weapons on South Korean Soil?

At the recent Biden-Moon summit, South Korea agreed to become more actively involved with the U.S. Indo-Pacific strategy. Following the takeover of Afghanistan by the Taliban in August 2021, it is appropriate to discuss the future of the ROK-U.S. military alliance.

China is continuing its military buildup, and seeking to extend and strengthen its diplomatic influence across the region. Against this background, it is time for the United States to increase its military resources to counter Chinese adventurism.

Several nations are developing hypersonic ballistic and cruise missiles, either medium-range (following Trump’s withdrawal from the Intermediate-Range Nuclear Forces Treaty) or long-range. Chinese and Russian weapons systems are well advanced, and the United States has initiated or reactivated several hypersonic missile development projects under various names: the U.S. Navy’s Prompt Global Strike (PGS); U.S. Army’s Long Range Hypersonic Weapon; U.S. Air Force’s AGM-183 Air-launched Rapid Response Weapon and Hypersonic Attack Cruise Missile; and DARPA’s Tactical Boost Glide and Operational Fires and Hypersonic Air-breathing Weapon Concept.

As commentators have noted, though, the U.S. would have to find a place to deploy its missiles. Indeed, former U.S. Secretary of Defense Mark Esper explicitly suggested that U.S. allies, including Australia, Japan, and South Korea, should allow the United States to deploy hypersonic weapons to assist in the strategic deterrence of Chinese threats.

Any deployment of such U.S.-developed hypersonic missiles on South Korea soil would inevitably be strenuously resisted by China, much like THAAD in 2017, and could seriously unbalance South Korean foreign policy. Recently, however, Australia has categorically rejected any such deployment, and with none of the other regional allies happy to accept them, it seems that South Korea is off the hook.

There is no particular reason why the United States needs to deploy hypersonic weapons on South Korean territory. There are no specific high-value targets in China’s northeastern provinces, and other U.S. allies seem better placed for the U.S. Indo-Pacific Command to manage Chinese threats, such as Japan and the Philippines, not the mention the U.S. territory of Guam.

Nuclear ballistic missiles can be identified, tracked, and classified as incoming threats by missile defense systems, for example those established by the MDA, but PGS and medium-range hypersonic missiles equipped with conventional warheads cannot be intercepted by any missile defense system. It is unclear whether the U.S. prefers hypersonic-capable and conventional PGS weapons to the existing medium-range ballistic missiles with nuclear capability. This uncertainty opens an opportunity for South Korea, now that limitations on its indigenous missile development have been lifted. New South Korean medium-range ballistic missiles would supplement U.S. capability in countering Chinese military threats to Northeast Asian security, as well as deterring the North Korean military threat.

Other Issues Affecting the Future of the ROK-U.S. Alliance

Some of the frontrunners to be the next president of South Korea have spoken about making changes to the ROK military and to the command-and-control structure of the ROK-U.S. Combined Forces Command (CFC), but they have said very little about the future of the ROK-U.S. alliance. Some military commentators argue that South Korea should pay more attention to operational and tactical matters than to political and strategic issues. In that regard, there are a variety of topics to be considered.

An Expanding Alliance

First, from the U.S. perspective, rebuilding the alliance is a priority. During the Trump era, his transactional and populist approach opened up some deep divisions between South Korea and the United States. Biden is now working to repair the damage. More than that, however, he also wants to extend the scope of the alliance beyond its historic focus on threats to the Korean Peninsula by involving Seoul in the U.S. Indo-Pacific Strategy, a thinly-veiled project to contain China.

A related initiative targets common domain awareness, with the ROK military trying to up its game by taking new responsibility for space, electronic, information, and cyberwarfare. To this end, the first meeting of a newly established ROK-U.S. ICT cooperation committee was held on August 5. Also, the ROK Air Force has reorganized its combat development group into an air and space combat research group, so that it can share a Common Operational Picture with the U.S. Space Force. The ROK Army and the ROK Navy are also getting more involved with space; for example the Cheonro-an satellite now monitors the surrounding seas of the Korean Peninsula, including the East China Sea.

In addition, now that South Korea is explicitly committed to more involvement in regional security, including potentially acting with the USFK to contingencies in the South China Sea and Taiwan Strait, the scope of the ROK-U.S. alliance has broadened. Future roles and missions for the ROK-U.S. CFC will be hampered by disparities between the two militaries unless a combined combat development group is established. The Japan-U.S. alliance has benefitted from bilateral joint research and development projects, and something similar is needed for the ROK-U.S. alliance.

Changing Doctrines

Second, there is widespread agreement that attempts to strengthen the capacity of the ROK-U.S. alliance should focus on doctrinal standardization. The United States is currently undergoing a great transformation of its expeditionary forces. Thus, the U.S. Army is establishing three Multi-Domain Task Forces, for the Indo-Pacific, Europe, and the Arctic. The U.S. Marine Corps also has a new mobile, agile, and flexible force, the Marine Littoral Regiment, designed to fight in a contested maritime environment. Likewise, the U.S. Navy has its Expeditionary Advanced Base Operations concept, for which it wants to build light amphibious ships, rather than large LHDs or LHAs.

These changes to U.S. forces mean that South Korea’s military will also need to change to ensure the future success of the ROK-U.S. alliance. Specifically, South Korean forces must pursue both technological and doctrinal interoperability, so that they can effectively interface with the new operational concepts of the United States. An integrated ROK Army, Navy Air Force, and Marine Corps force has been suggested, which could then operate in combined units between the ROK and U.S. militaries at the squadron and battalion level. And perhaps the United States should be invited to serve as an advisor in developing the concepts and frameworks of Defense Reform 2050, currently under development by the MND.

New Platforms, New Cooperation

Third, now that South Korea is building an aircraft carrier, close liaison with the U.S. Navy and Japanese Maritime Self-Defense Force (JMSDF) is needed. With the navies of South Korea and Japan both building or refitting light aircraft carriers, close cooperation is essential to ensure maximum interoperability. The U.S.-U.K. agreement on cooperative CV operation is the obvious model to follow. A considerable degree of interoperability has already been established, due to the F-35B take-off and landing system, which is the same on the U.S. Navy’s CVs, but much more is possible. The U.S. Navy has built up a vast repertoire of skills and know-how, which should be shared with South Korea and Japan for mutual benefit in the operation of CVs.

Fourth, some operational and tactical improvements are necessary. For example, South Korea and the United States need to better coordinate their strategic assets with the JMSDF, specifically: intelligence, surveillance and reconnaissance assets such as Global Hawk UAVs; airborne early warning and control assets; air refueling tankers and heavy lift aircraft; aircraft carriers; and amphibious assets. Also, the U.S. Navy needs a permanent presence in the form of destroyers at South Korean naval bases; the current arrangements with a one-star admiral are inadequate to deter potential threats from North Korea and China. And the South Korean Agency for Defense Development should be working on more research and development projects together with the U.S. DARPA, such as how to operate Manned-Unmanned Teaming between the two fleets. NATO has a variety of cooperative arrangements between multiple countries, and some of these could be usefully emulated by the ROK-U.S. alliance.

In short, the ROK-U.S. alliance is at a time of transition, and a lot of changes will be required to maintain the strength and effectiveness of the alliance into the future. The next South Korean president will have plenty of work to do.


Most of South Korea’s presidential candidates are proposing policies toward the United States, China, and North Korea that simply rehash previous ideas from the left or right, and in any case are based on outdated and obsolete scenarios. The world has moved on, and the ROK-U.S. alliance needs to acknowledge the fact. When the next president of South Korea is inaugurated in May 2022, he or she will have a very full inbox: the continuing COVID-19 pandemic, ever worsening climate change, the regional impact of the U.S. withdrawal from Afghanistan, growing doubts about the dependability of Pax Americana, and uncertainty over the future of the global economy.

Some candidates have flirted with populism during the campaign, but South Korea’s foreign and security policy needs someone grounded in reality. Thus, it is greatly to be hoped that the next president of South Korea will have the necessary experience and qualifications in these areas, and that they will choose the very best people for the relevant cabinet appointments. It would also be helpful if he or she has clearly articulated their approach to the United States, China, and North Korea so that there is a mandate for change – because change is coming to the ROK-U.S. alliance, like it or not.