The prospect of sending the air defense system — the Terminal High Altitude Area Defense anti-ballistic missile system, more commonly called THAAD — to South Korea has been around for a few years . The issue flared at the end of 2015; China railed against the possibility of THAAD systems in South Korea even as Seoul denied that formal discussions with Washington had even taken place. That it would downplay the discussions makes sense: Seoul has to maintain economic and security relations with both the United States and China, and it has to contend with domestic political factions that oppose new military initiatives with the United States. Partly because of the outrage of the South Korean public over a potential intelligence sharing deal with Japan and the United States, officials in Seoul realized that such issues ought to be discussed quietly.