required one rocket per incoming warhead, whereas the attackers could place 10 warheads on a single missile at a reasonable cost. To further protect against ABM systems, the Soviet MIRV missiles were equipped with decoys; R-36M heavy missiles carried as many as 40. These decoys would appear as warheads to an ABM, effectively requiring engagement of five times as many targets and rendering defense even less effective. ABM Treaty The United States first proposed an anti-ballistic missile treaty at the 1967 Glassboro Summit Conference during discussions between U.S. Secretary of Defense Robert McNamara and Chairman of the Council of Ministers of the Soviet Union Alexei Kosygin. McNamara argued both that ballistic missile defense could provoke an arms race, and that it might provoke a first-strike against the nation fielding the defense. Kosygin rejected this reasoning. They were trying to minimize the number of nuclear missiles in the world. Following the proposal of the Sentinel and Safeguard decisions on American ABM systems, the Strategic Arms Limitation Talks began in November 1969 (SALT I). By 1972 an agreement had been reached to limit strategic defensive systems. Each country was allowed two sites at which it could base a defensive system, one for the capital and one for ICBM silos. The treaty was signed during the 1972 Moscow Summit on 26 May by the President of the United States, Richard Nixon and the General Secretary of the Communist Party of the Soviet Union, Leonid Brezhnev; and ratified by the US Senate on 3 August 1972. The 1974 Protocol reduced the number of sites to one per party, largely because neither country had developed a second site. The sites were Moscow for the USSR and the North Dakota Safeguard Complex for the US, which was already under construction. Missiles limited by the treaty The Treaty limited only ABMs capable of defending against "strategic ballistic missiles", without attempting to define "strategic". It was understood that both ICBMs and SLBMs are obviously "strategic". Neither country intended to stop the development of counter-tactical ABMs. The topic became disputable as soon as most potent counter-tactical ABMs started to be capable of shooting down SLBMs (SLBMs naturally tend to be much slower than ICBMs), nevertheless both sides continued counter-tactical ABM development. After the SDI announcement On 23 March 1983, Ronald Reagan announced the Strategic Defense Initiative, a research program into ballistic missile defense which would be "consistent with our