On March 31, 1982 President Reagan, addressing the US-Soviet strategic nuclear relationship, asserted that the Soviet Union had achieved a “definite margin of superiority.” 1 Previous presidents had been concerned about the growth of the Soviet strategic arsenal. Indeed, President Reagan had warned earlier that the United States was entering a period known as the “window of vulnerability,” 2 in which its land-based missile forces would be increasingly vulnerable to a Soviet preemptive first strike. This was, however, the first time an American president had suggested that the United States had actually fallen behind the Soviet Union in strategic might.