Presidents Biden and Yoon pledged to deepen and broaden the scope of the U.S.-South Korea alliance, but their success could depend on how China, Japan, and North Korea respond.

With fresh agreement on sharing costs for the nearly thirty thousand U.S. troops in South Korea, the Biden administration can now focus on bolstering the alliance and addressing challenges posed by C…

The Quad, composed of the United States, Australia, India, and Japan, is not a formal alliance. Still, the group has intensified its security and economic ties as tensions with China rise.

North Korea seeks to exploit major-power rivalries and weaken U.S.-South Korea ties with its ramped-up missile testing. Already, it has ratcheted up nuclear tensions on the Korean Peninsula to their …

The United States and South Korea should pursue an expanded nuclear agreement that supports the production of civilian nuclear power and enhances extended deterrence against the North Korean threat. …