History of Europe
The conflict between the advocates of a capitalist and a socialist economy and political system led to the Cold War, a forty-year argument between the United States and the Soviet Union, two of the countries which had worked together to win the Second World War and the two which had come out of it with the most powerful military forces.  They led respectively a Western Bloc and an Eastern Bloc, dividing Europe.  Each side wanted to promote their type of government.  People across the world feared a nuclear war because of the tension, and Europe, divided by the Iron Curtain, was assumed to be a probable battleground.