The Cold War was a period of tension between the United States and its allies against the Soviet Union and its allies from the 1940s to the early 1990s. They competed for power and influence in subtle ways rather than direct war. Major events like the rise of the Berlin Wall and Cuban Missile Crisis were related to Cold War tensions. The space race allowed both nations to showcase scientific capabilities as they tried to one-up each other technologically. The United States dropped the first atomic bombs on Hiroshima and Nagasaki in 1945, remaining the only nuclear attacks against a population.