 Over 70 million people, the majority of them civilians, were killed, making it the deadliest conflict in human history.The Cold War was the state of conflict, tension and competition that existed between the United States and the Soviet Union and their respective allies from the mid-1940s to the early 1990s.Throughout this period, rivalry between the two superpowers was expressed through military coalitions, propaganda, espionage, weapons development, industrial advances, and competitive technological development, which included the space race.