The Post-Attack Command and Control System, or PACCS, was a set of United States military systems designed to ensure that National Command Authority would retain sole, exclusive, and complete control over US nuclear weapons. Among other components, it included Strategic Air Command assets such as the LOOKING GLASS aircraft and mission, and various hardened command and control facilities such as The Notch.
The belief by the Soviet Union in the reliability of PACCS was a crucial component of the US mutual assured destruction doctrine (ensuring a long term stalemate; see also, game theory).