The term 'defense acronym' refers to abbreviations used by the military and other defense organizations. The acronym SAC stands for Strategic Air Command, a former United States Air Force organization responsible for the strategic bombing of the Soviet Union during the Cold War. DEW stands for Distant Early Warning, a system of radar stations in the Arctic region used to detect incoming Soviet bombers. MIRV stands for Multiple Independently-targetable Reentry Vehicle, a type of ballistic missile with multiple warheads. NATO stands for North Atlantic Treaty Organization, a military alliance between North American and European countries formed in 1949. Finally, NORAD stands for North American Aerospace Defense Command, a joint US-Canadian organization responsible for aerospace warning, air sovereignty, and maritime warning in North America.