During the Cold War era that followed World War II, the threat of foreign attack on U.S. soil shifted from naval assault to air attack, particularly by aircraft carrying nuclear weapons. Thus, the Army Air Defense Artillery took responsibility from the Coast Artillery branch for defending the continental United States. In the San Francisco area, antiaircraft defenses were at a continual high state of readiness from the Korean War and through to the implementation of the Strategic Arms Limitation Treaty of 1972. Coastal defenses around San Francisco during this period largely depended on the Nike antiaircraft missile system. The Nike system was not only the most expensive missile system ever deployed, it was also the most widespread (300 sites in 30 states) and longest-lived (25 years nationwide). The system was deployed to protect urban areas throughout the U.S., bringing Doctor Strangelove to suburban backyards and into the national consciousness.