Catalyst for Containment Policy

Following the conclusion of World War II in 1945, the United States found itself navigating a complex geopolitical landscape that led to the onset of the Cold War. During this period, competition for global influence intensified between the U.S. and the Soviet Union, resulting in various political, economic, and ideological conflicts. One major turning point was the introduction of the policy of containment, which aimed to prevent the spread of communism. Understanding the origins of the Cold War requires examining key events, policies, and doctrines that shaped the post-war world.

Which of the following events is considered a direct catalyst for the United States' adoption of the containment policy, ultimately influencing its strategic approach to the USSR and worldwide communism?