The Cold War was a period of geopolitical tension between Western capitalism led by the United States and Eastern communism led by the Soviet Union. There was no direct military conflict, but instead tensions manifested as threats, espionage, propaganda, and competitive expansion of military capabilities and alliances. Key events during the Cold War included conferences in Tehran, Yalta, and Potsdam to discuss strategy against Germany and establish spheres of influence in Europe. Winston Churchill's 1946 "Iron Curtain" speech drew attention to the growing divide between Eastern and Western Europe. In response, alliances like NATO and the Warsaw Pact formed to counter the military capabilities of the opposing bloc.