Military power always has been, and remains today, the core of each country's national security policy. However, since at least the mid-1980s, arms control has assumed an increasingly important supporting role. During the waning days of the Cold War, the U.S. and U.S.S.R. began to use arms control agreements seriously as a means of breaking the periodic cycles of military arms build-ups that were proving unsustainably expensive to both sides. By the end of 1987, the two superpowers had agreed to the total elimination of two classes of ground based intermediate-range missiles, had begun to make major progress on deep reductions in their strategic offensive arms, and had laid the basis for unproved verification provisions for nuclear testing accords designed to slow development of nuclear weapons of ever larger yield.
During and following the break-up of the Warsaw Pact in 1989, the reunification of Germany in 1990, and the dissolution of the Soviet Union in early 1992, arms control agreements were the principal instrument used to deal with the new military realities reflected in the transition from Cold War bilateralism to emerging multilateralism. In Europe, the agreements were used to codify deep cuts and to create new parity in conventional weapons systems and military personnel. Globally, they became a central element in dealing with the emerging threat of a more rapid proliferation of weapons of mass destruction—nuclear, chemical, and biological weapons. New agreements achieved in the 1990s established global bans on chemical weapons, nuclear testing at any level, and on landmines and led to unproved biological weapons verification measures. Increasingly arms control verification measures, particularly on-site inspections, also have been applied to regional peacekeeping agreements, such as those in Iraq following the Persian Gulf war, in Korea in connection with its nuclear weapons program, and in Bosnia under the Dayton Agreements. Other arms control agreements, such as the Open Skies Treaty and the Vienna Documents have added new confidence-building inspections.