Sending Kentucky to Korea 

On July 18, 2023, the USS Kentucky, an Ohio-class ballistic missile submarine, docked in Busan, South Korea. The USS Kentucky is one of 14 Ohio-class submarines tasked with conducting nuclear deterrence patrols and carries up to 20 Trident II D5 nuclear-armed ballistic missiles. This visit marks the first port call by a nuclear-capable submarine since the 1980s and the 1991 decision to withdraw US nuclear forces from the Korean Peninsula.

This visit follows the recent June 16 port call by the USS Michigan, one of four conventionally-armed variants of the Ohio-class. That visit came on the heels of recent North Korean missile tests in protest of US-South Korea live-fire military drills, which were aimed at countering a potential North Korean attack.

These visits are significant due to their historically invisible presence due to their immense sensitivity and importance in US national security; however, the deployment is a very clear show of force meant for audiences in Pyongyang as tensions ramp up on the Korean peninsula.

Michigan and Kentucky: Arms and Armament

 The USS Michigan is one of four Ohio-class subs to undergo conversion to a non-nuclear conventionally armed cruise-missile submarine (SSGN) capable of carrying 154 Tomahawk missiles or sixty-six Navy SEALs which can launch from the first two missile tubes to conduct special operations missions. Even without nuclear weapons, USS Michigan is formidable given its payload of 154 Tomahawk missiles is 15% of the entire 2,300 that have ever been fired in combat since its induction in 1983.

The USS Kentucky is an Ohio-class submarine that joined the fleet in 1983 and continues to carry the United States’ nuclear forces at sea. Equipped with 20 launch tubes for the Trident II D5 missile which carries on average four nuclear warheads per missile, a single Ohio submarine could carry a nuclear payload 1,100 times more powerful than the two bombs combined that were dropped in 1945, even abiding by treaty limitations.

More Nukes, Less Nukes, the Same Nukes?

According to the CSIS database of North Korean provocations, since 2022, the Democratic People’s Republic of Korea (DPRK) has conducted 53 unique missile launches with roughly 123 ballistic and cruise missiles lifting off from across the Korean peninsula. In 2022, North Korea conducted record missile tests, more than doubling their previous peak in 2017 which coincided with an underground nuclear test in the same year. While 2023 is not on track to meet that pace as of now, there was a notable uptick in launches towards the end of the year in 2022 which, if repeated, may indicate a new norm. Additionally, North Korea has made significant progress in all aspects in its missile programs from reliability, survivability, fueling, and diversification. In April, North Korea successfully test-launched its first solid-fueled ICBM simplifying maintenance and supporting infrastructure for its nuclear forces. These advances do not metaphorically “change the game” however they do note the growing threat and tangible advancement of the North Korean missile program.

These tests provoked a strong reaction in South Korea and Washington alike. In Korea, according to a Chicago Council on Global Affairs poll, 71% of South Koreans now support nuclear weapons on their territory, including domestic development. In January of 2023, President Yoon told officials in the Defense and Foreign Affairs ministries that if the threat posed by North Korea “gets worse,” it is possible that “our country will introduce tactical nuclear weapons or build them on our own.” He further said that if the decision were made to develop nuclear weapons, Seoul could build them “pretty quickly, given our scientific and technological capabilities.”

These missile tests have also reignited the debate in Korea about whether Washington would honor its security guarantees if South Korea were to be attacked. This is a question that decision-makers under the US nuclear umbrella in Korea are questioning more seriously as China and North Korea are rapidly modernizing and expanding their nuclear arsenals.

Back in April, South Korean President Yoon Suk Yeol traveled to the United States to meet with President Biden. At the forefront of this visit was the North Korean missile tests and rising tensions between the two nations on the thirty-eighth parallel.

As a result, the United States and South Korea agreed to a litany of measures aimed at strengthening deterrence and increasing military cooperation. Under the new Washington Declaration, the United States committed to enhancing deployments of strategic assets, and “in particular US nuclear-capable platforms.” In return, South Korea has agreed to not develop its own nuclear weapons sating Washington’s fears of a wider proliferation event. Additionally, they committed to expanding military communications, exercises, and education across all spectrums as well as adding Japan to military exercises as the United States seeks to bolster its alliances and aid President Yoon’s push to mend Korean-Japanese relations.

The surfacing of the Kentucky and Michigan appear to be just the beginning of the increased deployments and military cooperation mentioned in the Washington Declaration. On June 30, 2023, US nuclear-capable bombers overflew the Korean peninsula in a joint exercise with the South Korean Air Force and, on July 18, 2023, the United States and South Korea convened the inaugural Nuclear Consultative Group (NCG) meeting to discuss deterrence and defense cooperation.

What Does It Mean for the United States and Korea?

For the United States, these new commitments are increasingly important as the US government seeks to strengthen its alliances and forces in Asia to manage potential Chinese and North Korean threats. The recent agreements tangibly expand upon this goal through its commitments to larger multilateral military exercises, longstanding policy against nuclear proliferation, and strategic force rotations which align with the US government’s increased investments and strategy in the Indo-Pacific region.

Current US alliances in Asia remain heavily bilateral, with longstanding US allies historically refusing to cooperate even with a shared partner. The most notable example is South Korea and Japan, two of America’s strongest allies which have staunchly opposed integration due to longstanding issues of colonization and wartime crimes spanning hundreds of years. However, given recent security issues, South Korean President Yoon and Japanese Prime Minister Kishida have made efforts to bury old wounds and make diplomatic progress between the two nations.

With two major US allies beginning to warm up to each other, the United States is able to form a stronger coalition in Asia if a security event were to break out. This would not only ease communication between the partners helping to coordinate efforts but also allow the partners to develop common responses, permit joint-military operations, and unity in crisis time. Furthermore, as the US military further commits assets to the Indo-Pacific, the increased capabilities that US strategic assets provide align with the DOD’s larger mission of deterring China, and protecting its interests in the region.

For South Korea however, while these assets may provide the public the security guarantees and reassurances they have sought, South Korea is also accepting a larger role in the US nuclear mission in Asia. That growing role raises the cost for adversaries, but also for South Korea. America’s rotation of strategic forces in Korea serves a dual purpose: (1) reaffirm US commitment to defending Korea, and (2) remind adversaries of the cost of an attack on South Korea.  However, in the event of a wider conflict, South Korea is a more valuable target for adversaries targeting American forces. America does base its forces extensively in Korea, with nearly 30,000 service members on the peninsula. If American forces do not operate from Korean soil, Korea may be exempt from being dragged into a conflict. Despite this, with US strategic forces docking in Korean ports and on Korean airfields, an adversary may decide a strike of sufficient value on these forces or their ability to operate may outweigh the risk of bringing Korea into a conflict.

The Next Decade

In the near term, expect to see a surge of US deployments of strategic assets to the Korean peninsula, such as the surfacing of Ohio-class submarines and the overflight of B-52 bombers. If the situation deteriorates further and missile tests continue at an increased pace, then deployments of more advanced assets may follow in greater numbers. In the longer term, if the North Korean situation continues to deteriorate, then South Korea may be one of the first overseas hosts of new US B-21 bombers and Columbia-class submarines, both of which will carry the newest generation of US strategic power. Alternatively, the public and government may once again call for an indigenous nuclear capability despite the cost of straining their relationship with the United States. However, if missile tests taper off, and the public cries fall silent, a more regular routine of US assets in Korea may return.

As of now, South Korea will not develop its own indigenous nuclear capabilities. Doing so would severely fray ties with the United States, invite international condemnation, and further spiral the North Korean crisis. However, the United States must continue to be flexible with its deterrence posture to reassure South Korea that its extended deterrence commitments remain credible and the United States must clearly communicate what steps it is willing and able to take. As of now, it appears the United States and South Korea are step-in-step and both parties are satisfied, however, a severe crisis may tip the scales in ways the alliance cannot yet predict.

China and North Korea have both condemned the Washington Declaration as many expected. The Chinese Foreign Ministry spokesperson noted, “What the US has done stokes bloc confrontation, undermines the nuclear non-proliferation system and hurts the strategic interest of other countries. It has also increased tensions on the peninsula and jeopardized regional peace and stability.” Meanwhile, Kim Yo-Jong, Kim Jong-Un’s sister, avowed more provocative displays of its military might.

Both of these messages, while expected, have only underscored the rationale in Washington and Seoul. From a South Korean view, this looks like China ignoring significant and real concerns about the North Korean missile regime once again. Up north, Pyongyang is repeating the same rhetoric as before, but now must be ever more cognizant of the American nuclear enterprise that looms over their heads and off their coasts. If anything, these public messages have only reaffirmed the necessity of US commitments to South Korea. For South Korea and the United States, this agreement makes positive progress in defending South Korea, enhancing US partnerships in the region, and preventing a potential widespread proliferation event. While the full extent of the deal is yet to materialize, it may be the start of a significant change to the US force posture on the Korean Peninsula and is worth watching closely in the coming years.

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The views expressed in this article are those of the author alone and do not necessarily reflect the position of the Foreign Policy Research Institute, a non-partisan organization that seeks to publish well-argued, policy-oriented articles on American foreign policy and national security priorities.

Image: U.S. Navy (Photo by Mass Communication Specialist 1st Class Michael Chen)