What was the primary reason the United States engaged in the proxy wars in Korea and Vietnam?

The United States engaged in the proxy wars in Korea and Vietnam primarily to contain the spread of communism. During the Cold War, U.S. foreign policy was largely influenced by the belief in the Domino Theory, which posited that if one country fell to communism, neighboring countries would follow suit, leading to a broader regional impact. The U.S. aimed to prevent the expansion of communist influence, particularly in Asia, where the Korean War (1950-1953) and the Vietnam War (1955-1975) unfolded. The primary objective was to support governments and forces that were opposing communism, even when it meant involvement in conflicts where direct military control was not established.

Supporting this effort were various geopolitical and ideological motivations, including the desire to support allies under threat from communism and to reinforce the United States' role as a global leader in promoting capitalism and democracy. However, the focus remained on containing communism, which drove military and economic assistance to nations that were seen as vulnerable to communist takeover.