During which conflict did the United States formulate the policy of containment?

The policy of containment was formulated during the Cold War, which marked the ideological struggle between the United States and the Soviet Union following World War II. The main goal of containment was to prevent the expansion of communism beyond where it already existed. This strategy emerged in response to fears that Soviet influence would spread throughout Europe and Asia, particularly after events such as the Berlin Blockade and the Korean War.

Containment was articulated in various documents and speeches, notably in George Kennan’s "Long Telegram" and the Truman Doctrine, which clearly framed the geopolitical landscape of the time. The United States aimed to counter Soviet influence in various regions through military, economic, and diplomatic means.

This context distinguishes the Cold War from earlier conflicts, such as World War I and World War II, which involved different strategies and outcomes. Likewise, while the Vietnam War was a significant conflict during the Cold War, it was not the time when the policy of containment was first formulated; rather, it was an application of the broader containment strategy developed earlier.