Before becoming President, Dwight D. Eisenhower served in which war?

Dwight D. Eisenhower served as a key military leader during World War II, which is the correct answer to this question. He held the position of Supreme Commander of the Allied Expeditionary Forces in Europe, where he was responsible for planning and executing major operations, including the D-Day invasion of Normandy in 1944. His leadership during this pivotal conflict played a significant role in the defeat of Nazi Germany.

In contrast, while Eisenhower did serve in the military during World War I, his most notable contributions came during World War II. He did not serve during the Korean War, as he became President shortly after the war began and was involved in overseeing the conflict rather than fighting in it. Additionally, he had no direct involvement in the Vietnam War, which unfolded later in the 1960s during the presidency of Lyndon B. Johnson. Thus, understanding Eisenhower's military background reinforces the significance of his leadership in World War II, making this the correct response.