The Battle of St. Mihiel is of singular significance in the history of United States participation in World War I. It was the first battle in France in which an American army fought under the American flag. The U.S. offensive gained all objectives quickly and with relatively few casualties. It eliminated a menacing salient that had threatened the Allied battleline for four years, and it cleared the way for new offensives that would end the war in less than two months. Aerial operations at St. Mihiel made the battle an important event in the history of U.S. Military aviation. It was, primarily, Col. William ("Billy") Mitchell's show. He put together the largest air force ever committed to battle and drew up the plan for its employment. This volume presents documents relating to the role of U.S. aviation in the Battle of St. Mihiel. It is the third in a series of four volumes that the Office of Air Force History is publishing on the U.S. Air Service in World War I.