The major event that initiated the Cold War between the United States and the Soviet Union was the end of World War II in 1945, particularly the tensions related to post-war arrangements and power dynamics. The differing ideologies of capitalism, represented by the U.S., and communism, represented by the USSR, created a climate of distrust. Key incidents, such as the Soviet occupation of Eastern Europe, the Berlin Blockade, and the race for nuclear arms, exacerbated tensions. These conflicts led to a bipolar world order characterized by political, military, and ideological rivalry, defining international relations for decades after the war.