In July 2016, the United States and South Korea announced the alliance decision to deploy a U.S. Terminal High Altitude Area Defense (THAAD) antimissile battery in South Korea to defend against the increasing North Korean missile threat. The move has angered Beijing, which perceives THAAD as mostly directed at China and a regional security concern, according to its official statements. In response, Beijing has used economic coercion, among other levers, to try to compel Seoul to abandon the THAAD deployment, but these efforts have proven unsuccessful. This report includes an overview of the THAAD system and its deployment, China’s stated concerns about THAAD, and China’s array of pressure directed against South Korea. It also examines the implications of China’s forceful response to the deployment for the United States and the geopolitical landscape in the Asia Pacific.