How to think about the big new nuclear alliance between the U.S. and South Korea

While Joe Biden may not be planning to stash any nuclear bombs on land around Seoul, make no mistake: Giving South Korea a voice in U.S. nuclear policy is a major development — a strategic shift that underlines how the White House views the country as a central player in its emerging strategy to counter China and its allies in the Pacific.

The Washington Declaration was launched as part of South Korean President Yoon Suk Yeol’s state visit to Washington this week. Only the second foreign leader to receive a state visit during Joe Biden’s presidency, Yoon took office last year facing a mounting North Korean military threat and a domestic public that’s increasingly questioning the U.S.’s willingness to defend South Korea as part of their mutual defense treaty.

Yoon raised eyebrows in January when he suggested Seoul could develop its own nuclear arsenal in response to North Korean dictator Kim Jong Un’s program, which now includes both tactical nuclear weapons and intercontinental ballistic missiles.

The new declaration could put to rest those rumblings for now. As part of it, Yoon recommitted South Korea to abiding by the Nuclear Nonproliferation Treaty, which forbids the development of nuclear weapons by any country beyond the five permanent members of the U.N. Security Council. “Our countries have decided to significantly strengthen extended deterrence against the North Korean threat,” Yoon said at a joint-press conference with Biden at the White House.

The Washington Declaration is best understood as part of the Biden administration’s broader effort to create a network of military alliances and partnerships around the Pacific meant to push back against China’s growing power. This includes its work with the Quad countries — Japan, Australia, India, and the U.S. — which conduct military exercises together, and the four new military sites the Pentagon is jointly developing in the Philippines. President Ferdinand Marcos Jr. will make his own state visit to Washington next week.

These alliances all exist independently, and U.S. officials have been insistent that they are not looking to create any kind of NATO equivalent in the Pacific. Still, the Biden administration is clearly attempting to create an unofficial united front as part of its counter-China strategy. U.S. diplomats have been aggressively working to end decades of animosity between South Korea and Japan, for instance. Biden lauded Yoon on Wednesday for his outreach to Tokyo that Washington hopes will lead to normalized diplomatic and economic relations and a strategic partnership on security matters.

It also wouldn’t be a surprise to see South Korea eventually join the AUKUS military development alliance that currently involves Australia, the U.K., and U.S. In its first stage, the three countries are jointly building nuclear-powered submarines. But Biden administration officials envisage a second phase that involves more countries developing high-tech military technologies, such as hypersonic weapons and quantum computers. The U.S. and South Korea announced Wednesday a new bilateral partnership to develop quantum technologies.

A number of North Korea watchers on Wednesday welcomed the Washington Declaration as an important step in aligning U.S. and South Korea. But some also doubted that the pact will deter North Korea in the long run or head off moves by South Korea and Japan to eventually seek their own nuclear weapons.

A poll conducted this month by South Korea’s Asan Institute found that 64% of the public supported the country acquiring nuclear weapons, compared to 33% who don’t. This is driven partially by North Korea’s rapid military advances and Kim Jong Un’s call for “offensive” nuclear weapons. But it’s also tied to concerns about U.S. domestic politics and growing calls for Washington to play a less interventionist role in the world.

Joel Wit, who was a senior diplomat working on North Korea in the Bill Clinton and George W. Bush administrations, said the North Korean nuclear threat will likely grow, as will the calls in Seoul either for the U.S. to redeploy tactical nuclear weapons on the Peninsula or for Seoul to get its own. “Bottom line: we are on the road to the nuclearization of Northeast Asia,” he said.

North Korea is expected to react angrily to the U.S.-South Korea summit and declarations. Kim Jong Un has been expanding his nuclear capabilities, he says, in response to increasingly aggressive U.S.-South Korean wargaming on his borders. Earlier this month, he launched for the first time a solid-fueled ICBM that has the potential to hit the U.S. mainland. News of the U.S. deploying nuclear-armed subs to South Korea could give him more rationale to grow his arsenal.

Beijing has repeatedly charged that the U.S. is seeking to contain and encircle China. And it has warned U.S. allies, like the Philippines, against hosting American military assets and war games.

China’s foreign ministry spokeswoman Mao Ning told reporters in Beijing that Washington and Seoul should avoid “deliberately stirring up tensions, provoking confrontation, and playing up threats” from North Korea, and urged them instead to “play a constructive role in promoting a peaceful settlement of the issue.”