While participating in the St. Mihiel Offensive, which was undertaken to eliminate the salient in the front lines around St. Mihiel that had existed since early in the war, the 13th fought with vigor. While ground forces were attacking and destroying, men, material, and morale, the 13th's pilots kept busy destroying enemy aircraft and balloons, and making the sky safe for Allied observation planes. The squadron suffered its first combat loss on 13 September when Lt. Robert Converse was shot down on a late afternoon patrol and reported missing in action. On 14 September 1918 a squadron-strength patrol led by Charles Biddle was ambushed by a flight of the red and white Fokker D VII aircraft of "Jasta 18", led by "Leutnant der Reserve" August Raben, one of a number of times the same two opposing squadrons would meet before the Armistice, starting with the aerial action over the St. Mihiel salient. Four original squadron members were downed in a matter of minutes: Lt. Charles Drew, Lt Alton Brody, Lt. Harry B. "Buck" Freeman and Lt. George P. Kull. Lts. Converse, Drew, Freeman and Brody were captured and repatriated after the Armistice. George Kull was confirmed killed in action, the first combat fatality of the 13th Aero Squadron.