Which event solidified the U.S. commitment to containment during the Cold War?

The formation of NATO (North Atlantic Treaty Organization) is the event that solidified the U.S. commitment to the policy of containment during the Cold War. Established in 1949, NATO was a collective defense alliance that included the United States and several Western European nations. Its primary purpose was to counter the perceived threat of Soviet expansion and to ensure mutual defense among member states.

By joining NATO, the U.S. formally committed to aiding its allies in the event of a Soviet attack, which directly reinforced the containment strategy aimed at preventing the spread of communism. The establishment of NATO marked a significant shift in American foreign policy, moving from isolationism to a more active role in global security matters. This alliance was based on the principle that an attack against one member would be considered an attack against all, thereby deterring Soviet aggression in Europe and contributing to the broader containment strategy.

The other options, while significant in their own right, either do not directly pertain to containment or occurred in different contexts. For example, the bombings of Hiroshima and Nagasaki were pivotal in ending World War II and demonstrate the U.S.'s nuclear capabilities but do not relate to the containment of communism specifically. The establishment of the United Nations aimed at fostering international cooperation