Iron Curtain: The metaphorical division between communist Eastern Europe (controlled by the USSR) and democratic Western Europe.
Berlin Wall: A physical barrier constructed by the German Democratic Republic (East Germany) that divided West Berlin from East Berlin and prevented movement between the two parts of the city.
Truman Doctrine: A policy implemented by President Truman stating that the United States would provide political, military, and economic assistance to all democratic nations facing internal or external threats.