During the Cold War and particularly during the 1980s, the major powers, especially the United States and the Soviet Union devoted enormous resources competing to maintain the largest arsenals, conventional and nuclear, in human history.
With the collapse of the Soviet Union in 1991, many expected there would be a significant "peace dividend" resulting from global disarmament. Yet in 1999 the United States is spending as much annually on the military as it did on average annually during the entirety of the Cold War, with adjustment for inflation.
This level of resources -- $289 billion authorized for the U.S. Defense Department for fiscal 2000 -- is justified by policy adopted by the Joint Chiefs of Staff in 1990 and by the Defense Department in 1993 named the "Bottom-Up Review", which determined that the United States should be prepared to win two simultaneous major regional conflicts -- area-wide wars -- with no allies, and the latter's update, the Pentagon's Quadrennial Defense Review in 1997.
Threats were envisioned from adversaries like North Korea, Iran, Iraq, Syria and Libya. This policy underpinned maintaining large numbers of troops, fleets, air and land power and armor, high-technology research and development as well as substantial nuclear capacity. There was virtually no public debate on this policy, nor on the subsequent Congressional authorizations and appropriations.
Under Start I and Start II, the United States and the Soviet Union, followed by Russia, agreed to reduce nuclear weapon capacity significantly, though approval of Start II has been stalled in the Russian Duma.