The Col War was the period of conflict, tension and competition between the United States and the Soviet Union and their respective allies from the mid-1940s until the early 1990s. Throughout this period, the rivalry between the two superpowers unfolded in multiple arenas, such as military coalitions; ideology; psychology; espionage; and military, industrial, and technological developments, which included the space race. In sports, rising tensions between the US and the USSR led to boycotts of major events. The Cold War generated for both superpowers costly defence spending, a massive conventional and nuclear arms race, and many proxy wars.