What major conflict did Eisenhower serve in before becoming President?

Dwight D. Eisenhower served as the Supreme Commander of the Allied Expeditionary Forces in Europe during World War II. His leadership was instrumental in planning and executing the D-Day invasion, which marked a significant turning point in the war. His military experience and visibility during this decisive conflict contributed significantly to his later election as President of the United States.

World War II was a defining event in Eisenhower's career and helped shape his policies and approach as President, particularly during the Cold War era. Understanding his role in World War II provides important context for his foreign and domestic policies while in office.

The other conflicts mentioned, such as the Civil War, Korean War, and Vietnam War, occurred at different times and were not part of Eisenhower's military service. Therefore, they do not accurately represent the major conflict he was involved in prior to his presidency.