From the Overview: "South Korea (officially the Republic of Korea, or ROK) is one of the United States' most important strategic and economic partners in Asia. The U.S.-ROK Mutual Defense Treaty, signed in 1953 at the end of the Korean War, commits the United States to help South Korea defend itself, particularly from North Korea (officially the Democratic People's Republic of Korea, or DPRK). The alliance also helps the United States promote its interests in East Asia and around the globe, including by deploying ROK troops to U.S.-led military conflicts in the Middle East. [...] On May 21, President Joseph Biden and ROK President Moon Jae-in are scheduled to meet in Washington, DC. The meeting, Biden's second in-person summit after one with Japan's prime minister, appears to signal the Administration's priority on the Indo-Pacific region and on reinvigorating U.S. alliances. Under the Trump Administration, the U.S.-ROK alliance was strained by disputes over South Korean contributions to cost-sharing arrangements to host U.S. troops. During the upcoming summit, the two leaders reportedly are expected to discuss North Korea policy, a Coronavirus Disease 2019 (COVID-19) vaccine partnership, the challenges of dealing with China's rise, U.S.-South Korea-Japan coordination, and cooperation to make semiconductor supply chains more resilient."
CRS In Focus, IF10165
Congressional Research Service: https://crsreports.congress.gov/