FAQ: How did Truman gain the experience necessary to command an artillery unit in France in WWI?
Harry S. Truman joined the National Guard in 1905, while working at the Union National Bank in Kansas City, advancing to the rank of corporal. After the declaration of war by President Wilson, on April 6, 1917, the members of his battery elected Truman a first lieutenant. He attended artillery school and regimental school while at Camp Doniphan, in Oklahoma, and in France, where he was promoted to Captain of Battery D.
Source: The Autobiography of Harry S. Truman, edited by Robert H. Ferrel, Colorado Associated University Press, ©1980, pp. 27 and 41.