another kind of war existed from 1947 until 1991 called the cold war. this started when diplomatic relations between the united states and the soviet union broke down. both countries had nuclear weapons and both stood ready to use them against the other. but there was no actual war between the two. it ended with the fall of the soviet union in 1991. the cold war was also called a containment where the united states tried to prevent the spread of communism to other countries. during the cold war, the major powers did not fight themselves, but often backed third parties in what was called a proxy war. the vietnam war is often given as an example of a proxy war. but proxy wars happened long before the cold war and are still happening.