Optimizing the United States–South Korean Alliance: A New Approach to Burden Sharing (Marcellus Policy Analysis)

By Thaddeaus Webb, Spring 2024 Marcellus Policy Fellow

In an era of multipolarity, the United States’ foreign policy faces insolvency. America remains tethered to military commitments across Europe, the Indo-Pacific, the Middle East, and Latin America. Many of these commitments could result in large-scale wars if the United States is faced with enforcing them. The U.S. military, however, is no longer designed to fight multiple major power conflicts simultaneously. If the U.S. military is decisively engaged in a large-scale conflict, then Washington risks defaulting on other security commitments.

To help address this gap between means and commitments, U.S. decision-makers should look for ways to shrink their overseas security obligations responsibly. Reimagining America’s responsibilities in the U.S.-Republic of Korea (ROK) alliance is an important step toward making U.S. foreign policy solvent again. In a future Korean Peninsula crisis or conflict, South Korea’s latent power potential allows Seoul to defend against and defeat any conventional North Korean attack through its own strength. Pyongyang, however, has a monopoly over Seoul on nuclear threats and dilutes South Korea’s military preponderance over North Korea. Seoul is likely unable to overcome this nuclear imbalance without the support of the United States.

This paper recommends America’s obligations in the US-ROK alliance resemble Great Britain’s formal obligations to Japan in the 1902 British-Japanese military alliance. This unique alliance was not focused on deterring an armed attack on Japan, but rather on preventing horizontal escalation. America’s treaty commitment to South Korea should solely consist of solidifying its nuclear deterrence posture (vertical escalation) while placing the conventional defense of South Korea on the shoulders of the ROK military. Burden sharing through a division of labor at the macro-strategic level will help reduce American military commitments abroad while offering Seoul a greater sense of security.