The key event that fueled the start of the Cold War was the division of Europe following World War II, particularly reflected in the contrasting ideologies of the United States and the Soviet Union. A critical moment was the 1946 "Iron Curtain" speech by Winston Churchill, which illustrated the growing divide between Western democratic nations and Eastern communist nations. The subsequent establishment of opposing alliances—NATO led by the U.S. and the Warsaw Pact led by the USSR—further intensified tensions. The ideological conflict over communism versus capitalism created an atmosphere of distrust, leading to proxy wars, the arms race, and a decades-long standoff.