Young Marshall was not a particularly good student in school, but he was particularly interested in history, and he developed the ability to interpret American society and specific problems he faced in a broad historical context. In later years, when asked to which political party he belonged, Marshall generally responded: My mother was a Republican; my father was a Democrat; and I'm an Episcopalian.

Marshall attended the Virginia Military Institute, graduating in 1901 as the highest-ranking cadet. He entered the U.S. Army in February 1902. For the next fifteen years, he served in various of the posts in the U.S. and the Philippines. Between 1906 and 1910, he attended army schools at Fort Leavenworth, Kansas, and also taught there. He was a member of the small group of U.S. Army officers trained in modern warfare prior to World War I.

He went to France in the summer of 1917 as the director of training and planning for the First Infantry Division. In mid-1918, he was promoted to American Expeditionary Forces headquarters, where he was a key planner of American operations. In 1919 he became an aide-de-camp to General John J. Pershing. Between 1920 and 1924, while Pershing was army chief of staff, Marshall was an important planner and writer in the War Department in Washington, D.C.

Following a tour of duty (1924-27) with the Fifteenth Infantry in Tientsin, China, Marshall was assigned to teach at the Army War College, but when his wife died, he was moved to the Infantry School at Fort Benning, Georgia, to become head of instruction. There he reformed army infantry officer training to prepare for a war of mechanization, air power, and rapid movement. He briefly (1932-33)commanded posts at Fort Screven, Georgia, and Fort Moultrie, South Carolina, where one of his key duties was creating and running Civilian Conservation Corps camps. Between 1933 and 1936, he was in Chicago as senior instructor to the Illinois National Guard. He was promoted to brigadier general in October 1936 and given command of Vancouver Barracks, Washington, and its CCC district (1936-38).

Marshall returned to Washington to become head of the War Department's War Plans Division and then deputy chief of staff (1938-39), prior to being selected by Franklin D. Roosevelt to be army chief of staff (1939-45). Highly regarded by his peers, leaders of the Roosevelt administration, and members of Congress, Marshall was in charge of getting the U.S. Army and Army Air Corps ready for war (1939-41), reorganizing the army (1942), and leading it throughout the war. He was the most important member of the Joint Chiefs of Staff and, according to Winston Churchill, the organizer of Allied victory.

Marshall "retired" in November 1945, but President Truman immediately asked him to go to China to attempt to mediate a settlement between the Nationalists and Communists. In January 1947 he was named secretary of state. In that role, his name is most commonly associated with the "Marshall Plan," for which he won the Nobel Peace Prize in December 1953. In 1949 he resigned from the State Department and was soon named president of the American National Red Cross, hardly a sinecure, given the organization's troubles at the time. In September 1951, three months after the outbreak of the Korean War, Truman asked him to become secretary of defense, a job he held for a year. Marshall died at Walter Reed Hospital on October 16, 1959, and is buried in Arlington National Cemetery.