Mikhail Gorbachev's perestroika has had its most conspicuous success in restructuring US.‐Soviet relations. The INF treaty with the United States and the talks now under way on a prospective START agreement are major developments in international arms control. But Soviet START proposals are a threat to nuclear deterrence. START reductions in strategic nuclear weapons will decrease U.S. security dangerously unless they are implemented under the vrotective umbrella of a U.S. missile defense syste