The key political ideology central to the conflict between the U.S. and Soviet Union during the Cold War was communism. The Soviet Union promoted a system where the government controls all means of production, aiming for a classless society. In contrast, the U.S. championed capitalism and individual liberties, advocating free markets and democratic governance. This fundamental ideological divide led to decades of tension, proxy wars, and a nuclear arms race, profoundly influencing global politics, economics, and security strategies during the latter half of the 20th century.