George C. Marshall served as Truman’s secretary of state from 1947 to 1949 and as his secretary of defense from 1950 to 1951. Marshall had been Franklin D. Roosevelt’s chief military advisor and was a key figure in Allied strategy during World War II. He won the Nobel Peace Prize in 1953 because of the famous program named after him—the Marshall Plan—which outlined the economic rebuilding of Europe following the devastating war.