In a June 1943 Allied raid against Kiel, Germany, German fighters swarmed 60 American B-17 bombers on attack. Twenty-two Flying Fortresses were lost. In July 1943, a U.S. raid against German aircraft factories outside of Berlin started out with 160 aircraft. Only 28 reached the target. Twenty-two were shot down. Morale sagged badly. The strategic bomber offensive was curtailed, pending arrival of fighter planes that could escort the bombers all the way to a target and back.