The cold war

just after World War II, the alliance between the United States, Britain and the USSR ended. A rivalry between communist and non-communist nations led to the Cold War. Germany was divided into four occupied zones controlled by Great Britain, France, the Soviet Union, and the United States. When the USA decided to drop the atomic bomb on Japan, the USSR was upset that America had secretly developed the bomb. Churchill and Truman were angry that Stalin had already signed a border treaty agreement with Poland. By 1948, Russia controlled Poland, East Germany, Hungary, Romania, Bulgaria and Czechoslovakia. Churchill was first to refer to this as an Iron Curtain that divided Europe. In 1949, Mao Zedong's communist forces had won a victory in China and this added another front to the Cold War. The United States believed that the Soviet Union's expansion threatened the developing nations of the world.