International Relations/The Cold War
The Cold War was a state of tension and distrust between the US and the Soviet Union, without actual fighting. The world "split" into two "camps"/military alliances [Western Europe and NATO vs. Eastern Europe and the Warsaw Pact]. These two countries competed with each other for just about nearly everything; including to spreading their own ideologies [Democracy and Capitalism vs Dictatorship and Communism], being the first into space (space race), having the most nuclear weapons (arms race), and having the best Olympic sports teams. The war was an ideological war something more or less like a mirage, it was just a perceived war in the head.
Read The Tragedy of Great Power Politics by John Mearscheimer, 2001 Chapters 4, 5, and 6