U.S. strategy shift raises stakes for South Korea

The Donald Trump administration’s new National Defense Strategy, released Jan. 23, states that South Korea has the capacity to take primary responsibility for deterring North Korea, adding that U.S. support for that effort will be important but limited. The strategy lists defense of the U.S. homeland as the top priority, followed by deterring China in the Indo-Pacific region. Analysts say the document signals a broader shift in which the United States will focus on its own core interests while expecting allies to shoulder greater security responsibilities.

The strategy marks a major turning point for U.S. Forces Korea, which for 73 years has focused primarily on deterring North Korea and now appears poised to pivot toward countering China. The NDS says changes in responsibility-sharing between South Korea and the United States align with U.S. interests in readjusting its military posture on the Korean Peninsula. It also calls for a strong defensive line against China along the first island chain, a key element of Washington’s containment strategy. Within that chain, U.S. Forces Korea is the only permanent U.S. military presence, signaling the command’s growing role in U.S. strategy toward China.

As U.S.-China strategic rivalry intensifies and the geopolitical security environment continues to shift, modernizing the alliance by recalibrating the role and scope of the South Korea-U.S. alliance has become an unavoidable trend. Still, restructuring U.S. Forces Korea must not go so far as to expose South Korea to the risk of being drawn into conflicts it does not seek. There must be no scenario in which the United States unilaterally makes decisions, without close consultation, that could undermine South Korea’s national interests, including turning the Korean Peninsula into a potential target of Chinese military action.

Any redeployment or restructuring of U.S. Forces Korea must also not weaken deterrence against North Korea. Regardless of U.S. demands, South Korea needs to strengthen its own defense capabilities given its exposure to North Korea’s military threats. At the same time, it is unrealistic to expect South Korea’s conventional forces alone to provide sufficient deterrence against North Korea’s nuclear arsenal. This is why a clear and unequivocal U.S. commitment to extended deterrence, including the provision of a nuclear umbrella for South Korea, must be a prerequisite.

Yet the latest NDS makes no mention of the nuclear umbrella. This contrasts with the NDS released four years ago, which emphasized extended deterrence to prevent North Korea’s use of nuclear weapons. Even more striking, last month’s joint statement from the Nuclear Consultative Group, the South Korea-U.S. dialogue mechanism on extended deterrence, did not mention North Korea at all. Regardless of how U.S. security strategy may evolve, the reality that North Korea poses an existential threat to South Korea does not change. Efforts to bring North Korea to the negotiating table will only be viable if they are backed by firm and credible deterrence against North Korean nuclear provocations, a point South Korea must continue to press with persistence and clarity.