Arms control during the Cold War had a mixed track record. SALT limited the number of ground and submarine launchers of ballistic missiles (according to President Ronald Reagan, the most destabilising weapons, as missiles cannot be recalled once fired, unlike bombers, and reach their targets in minutes rather than hours); on the other hand, it did not restrict the number of warheads, which continued to rise, especially on the Soviet side. The emergence of MIRVs in the 1970s allowed the US and USSR to compensate for curbs on missile numbers by mounting multiple warheads on each missile. US and Soviet military spending picked up in the 1980s arms race, reaching over 6 % of GDP for the US, and an economically ruinous 15 % of Soviet GDP.
Military budgets and the number of nuclear weapons fell dramatically in the 1990s. Not all of this reduction was due to arms control agreements: the easing of geopolitical tensions and Russia’s deep economic crisis meant that defence spending was no longer such a priority. In 1991 and 1992, the US and USSR/Russia took unilateral measures eliminating many thousands of nuclear warheads outside of the INF and START I treaties. However, START I and New START have also played an important part, by setting strict and equal limits for the two sides, together with far-reaching transparency requirements providing reliable information about numbers, locations and capabilities of each other’s nuclear forces. Arguably, these two treaties have enabled Russia and the US to go further than they might otherwise have done, by guaranteeing that each side’s reductions are reciprocated. Under New START, both the US and Russia continued to downsize their strategic nuclear weapon arsenals even after 2014, despite deteriorating relations between the two countries.