Throughout the Cold War, the U.S. and USSR threatened with all-out nuclear attack in case of war, regardless of whether it was a conventional or a nuclear clash. U.S. nuclear doctrine called for mutually assured destruction (MAD), which entailed a massive nuclear attack against strategic targets and major populations centers of the Soviet Union and its allies. The term "mutual assured destruction" was coined in 1962 by American strategist Donald Brennan. MAD was implemented by deploying nuclear weapons simultaneously on three different types of weapons platforms.