Deployed to England in January 1943, Sebille flew bombing missions in the European theatre. The 322nd Bombardment Group, the first unit to fly the B-26 Marauder, was sent on its first mission on May 14, a low-altitude attack on an electrical power plant in the Netherlands under the control of Nazi Germany. The mission was Sebille's first sortie, and the group suffered one plane lost and 10 damaged. Three days later a second attack was assigned on the same target, however, Sebille was not on the mission list. Of the planes that flew the mission, one aborted and the rest did not return. Sebille advanced to flight leader and then was promoted to squadron operations officer with a temporary rank of major. By the end of the war, Sebille had flown 68 combat missions with 245 combat hours. In the war he had been awarded two Distinguished Flying Crosses and twelve Air Medals. His unit returned to the United States in March, 1945.