the 351st's first completed combat mission took place on 14 may 1943, when 18 b-17's targeted a german luftwaffe airfield at kortrijk, belgium. as the war progressed, the 351st operated primarily against strategic objectives in germany, striking such targets as ball-bearing plants at schweinfurt, communications at mayen, marshalling yards at koblenz, a locomotive and tank factory at hanover, industries at berlin, bridges at cologne, an armaments factory at mannheim, and oil refineries at hamburg.