meant that warheads could be smaller. New warheads could be sized to detonate at kiloton or megaton ranges independently. Because they were smaller and lighter, more warheads could be mounted to each ICBM and SLBM. In the early 1970s the DOD developed MIRVs (multiple independently targetable reentry vehicles), allowing three or more warheads on each ICBM and SLBM. The Air Force's arsenal did not rise above 1,054 ICBMs; many now carried three MIRVs (Minuteman III) as opposed to earlier models that carried a single Minuteman I or II warhead. Strategic launchers remained static, but warheads multiplied.
Although Secretary of Defense McNamara introduced "counter-force" targeting in 1962, the improvement in CEP and dramatic increases in the number of nuclear warheads in the American arsenal of the 1970s encouraged the Air Force to return to the more traditional practice of bombing precise military targets instead of countervalue cities. Counterforce targeting identified enemy military and industrial chokepoints―command centers, military industries and bases, and ICBM silos. Whatever the targets selected, in the 1960s political leaders adopted a doctrine for deterring nuclear war known as "assured destruction," i.e., the capability to destroy an aggressor as a viable society, even after a well-planned and executed surprise attack on American forces. This doctrine held that superpower strategic nuclear forces would be sized and protected to survive a nuclear attack and then to retaliate with sufficient force to ensure a level of destruction unacceptable to the other side. With such retaliatory destruction assured against an aggressor, no rational Soviet or American leader would consider starting a nuclear war. On May 26, 1972, the United States and the Soviet Union signed the Anti-Ballistic Missile (ABM) Treaty, which limited both sides to two ABM sites each to protect the national capital and an ICBM complex. The treaty reinforced the continued effectiveness of assured destruction in deterring war in the face of new, destabilizing ABM weapons. SALT I, the Strategic Arms Limitation Treaty which was signed at the same time, limited the numbers of nuclear weapons with the objective of obtaining a verified freeze on the numerical growth and destabilizing characteristics of each side's strategic nuclear forces.
The Nixon administration adopted counterforce targeting beginning with SIOP 5 of 1974. The Carter administration expanded it with Presidential Directive 59 and SIOP 5D. Counterforce, however, offered an option to assured destruction of a limited, prolonged nuclear war based on accurate attacks with limited collateral damage while maintaining a creditable second strike capability. In an address on March 23, 1983, President Ronald Reagan proposed replacing the doctrine of assured destruc-
