The Cold War emerged after World War II as tensions grew between the Western powers (US, Britain, France) and the Soviet Union. Germany and Berlin were divided between the Western Allies and Soviet control. Over time, Eastern European nations fell under Soviet control as well, separated by an "Iron Curtain". The US and Western nations established policies and alliances like the Truman Doctrine, Marshall Plan, and NATO to contain the spread of communism and Soviet influence, engaging in a nuclear arms race and policy of brinkmanship with the Soviet Union. These tensions defined the Cold War era between the Western and Eastern blocs.