The Cold War
It was gigantic rivalry between two sides in Europe that began afterwards World War One, in 1945 - 1991. One side was the Western Bloc, dominated by the United States with NATO and other allies; versus powers in the Eastern Bloc, dominated by the Soviet Union with the Warsaw Pact and other allies. The two sides opposed each other and as the two main superpowers, worked to try and gain the upper hand of political influence on the world. The Soviet Union were trying to gain the influence of communism over several European countries while the United States and Britain took on the influence of Western and some southern countries.
However, this war was unlike any other war, because the two opposing sides' armies never directly went at war with each other. They had indirect wars like the Vietnam War, Korean War, etc which are also called proxy wars. Many people feared that the tenison between the two opposing sides would soon end in a nuclear war, but thankfully it never happened.