A2/AD

Anti-access/area-denial is a military strategy combining long-range sensors and weapons (anti-ship ballistic and cruise missiles, submarines, sea mines, integrated air defense) to deny an adversary’s forces entry into a theater (anti-access) or freedom to maneuver once inside it (area-denial). The term entered US Department of Defense usage in the 2000s; the 2010 Quadrennial Defense Review and the resulting Air-Sea Battle concept (2012) framed it against capabilities such as China’s DF-21D and DF-26 missiles. For shipping it signals waters where state-level conflict can close routes or raise war-risk exposure.