South Korea Reconsiders Its Security Future as U.S. Military Commitments Show Cracks

The South Korean marine corps said Monday that Washington had canceled joint drills originally scheduled for September, citing competing demands in Iran. The announcement comes days after President Donald Trump curtailed another round of high-profile defense exercises, noting that he was disappointed in South Korea’s refusal to help with the U.S. war in the Middle East.

In Seoul, the dual cancellations have added to the sense that U.S. military support has become conditional – and are reigniting calls for South Korea to develop its own nuclear arms.

Several U.S. allies around the world are facing the same challenge: If a country can no longer count on Washington’s support, it must pursue a more self-reliant approach to national security. But South Korea might be best poised to make an actual, radical change toward that end. The government under President Lee Jae-myung is relatively strong, as is South Korea’s economy, and security is top of mind for Korean voters. As the number of military-age men declines and the threat from Pyongyang grows, many are eager to shore up regional stability, but are also wary of getting dragged into other countries’ conflicts.

Why We Wrote This

Washington’s curtailing of joint military drills in South Korea was widely framed as a humiliating moment for Seoul. But it could also push the country on a path to self-reliance – and nuclear arms.

Acquiring nuclear weapons – a once-taboo notion that now has growing support among South Korea’s public – would dramatically shift the paradigm in northern Asia, and could cement South Korea’s spot in the new world order as a military power unto itself.

“The more transactional the alliance [with the United States] appears, the stronger the argument becomes in Korea for autonomous defense capabilities,” says Cheong Seong-chang, vice president of South Korea’s Sejong Institute and author of the 2023 book “Why We Should Become a Nuclear Power.” That includes “a debate about an independent nuclear deterrent.”

A TV screen shows an image of North Korean leader Kim Jong Un during a news program at the Seoul Railway Station in Seoul, South Korea, Sept. 13, 2024. The letters read, “North Korea, unveiling the uranium enrichment facility for the first time,” and “the construction site for expanding the capacity for the production of nuclear weapons.”

Nuclear taboo erodes

In Seoul, calls for a nuclear deterrent resurfaced in headlines this past week after Mr. Trump abruptly downscaled joint military exercises, saying they sent “a totally inappropriate and hostile” message to North Korea. A recent survey found about 80% of South Koreans believe the country should invest in becoming a nuclear state, up from about 64% in 2013.

Research shows that South Korea’s “strategic elites” – lawmakers, think tank experts, etc. – are generally less supportive of taking up nuclear arms than the general public. But nevertheless, the idea has been largely normalized after the country’s previous president floated it publicly in 2023.

“The taboo has substantially eroded,” says Christoph Bluth, a professor of international relations and security at the University of Bradford in England. “Nuclearization is increasingly treated as a legitimate strategic option, and further doubts about U.S. reliability could shift opinion quite rapidly.”

President Lee has not backed the development of nuclear weapons, but he has advocated for South Korea to take back wartime operational control from the U.S. In other words, he wants Seoul to call the shots if conflict again breaks out on the Korean Peninsula.

At the same time, South Korea has set its sights on using low-enriched uranium for nuclear-powered attack submarines, a technology possessed by only six other countries. (These submarines are not nuclear weapons, but some argue they challenge nonproliferation norms in the region.) The country also raised its annual defense budget by more than 7% this past year, the largest increase since 2019, and has set a goal to become one of the world’s top four defense exporters by 2030.

South Korean President Lee Jae-myung speaks during a ceremony to celebrate the 81st anniversary of the Korean Liberation Day in Seoul, South Korea, Aug. 15, 2026.

Experts warn that these efforts could backfire. South Korea has so far managed to avoid getting involved in the war in Iran, or in a contingency plan for a Chinese invasion of Taiwan, but not without some strategic maneuvering. Becoming a stronger military power and defense industry exporter could make that maneuvering harder.

“The paradox is that greater strategic autonomy may actually produce greater strategic engagement,” says Dr. Bluth. “The more indispensable South Korea becomes to regional security, the harder it will be to remain outside other countries’ conflicts.”

Costs of nuclear armament

If South Korea were to obtain nuclear weapons, it could face retaliatory sanctions for violating the Non-Proliferation Treaty that it ratified in 1975, after the U.S. pressured Seoul to abandon a nuclear program it was developing in secret. Washington succeeded, in part, by reassuring the country’s then-president that Seoul had America’s military backing.

“There is a tremendous amount of goodwill that South Korea has gained through its commitment to international law, global development, and the promotion of peace,” says Alexander M. Hynd, a lecturer at the University of Melbourne’s Asia Institute. “Going nuclear could seriously degrade Korea’s global reputation. … There are far better options that would strengthen regional security.”

Instead, South Korea could focus on upgrading its already high-tech conventional armed forces, and look for new ways to replenish its diminishing pool of soldiers. Polls have shown rising support for conscripting women, for example.

Some South Koreans, including peace activist Oh Mi-jeong, are steadfast in their opposition to nuclear arms.

A researcher at Solidarity for Peace and Reunification of Korea, Ms. Oh has spent decades advocating for a total disarmament of the Korean Peninsula. In recent weeks, she’s been busy preparing a people’s tribunal on the effect of U.S. atomic bombs in Japan, set for November.

These days, as pressure builds for South Korea to take its security into its own hands, her guiding principle remains straightforward: “Preparing for peace will lead to peace,” she says, “and preparing for war will lead to war.”

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