Final answer:
The Cold War was precipitated by the division of Europe after World War II into Western democracies, led by the United States, and Eastern communist blocs under Soviet control, alluding to Churchill's 'iron curtain' speech and the intensifying ideological rivalry.
Step-by-step explanation:
The event in World War II that led to the Cold War was the division of Europe after the defeat of Nazi Germany, resulting in a clear separation between Western democracies led by the United States and Eastern communist bloc countries dominated by the Soviet Union. This geopolitical split was symbolically captured by Churchill's "iron curtain" speech in 1946. The consequential ideological, military, and economic competition between the superpowers manifested in various forms, such as the arms race, the space race, and proxy wars, which all served to prevent a "hot" war directly between the nuclear-armed adversaries. Major incidents like the Berlin Blockade and the formation of opposing coalitions such as NATO and the Warsaw Pact further cemented the adversarial relationship, setting the stage for a multi-decade Cold War.