Aircraft as a submarine-suppression tool

Aircraft could force submarines below the surface, reducing their speed, range, and ability to recharge batteries. Air cover therefore mattered even when it sank nothing, building on British experience from the First World War. Fleet carriers offered mobile airfields from which hunting groups could dominate a large area, but they also concentrated enormous value in platforms exposed to the submarines being hunted. HMS Ark Royal narrowly escaped an attack, while the loss of HMS Courageous showed how costly that trade could be. The officially available 200-pound anti-submarine bomb was substantially lighter than the shipborne depth charges discussed earlier and appeared too weak except under unusually favorable conditions. The rising number of aerial submarine kills may have involved modified Mark VII depth charges or improvised weapons, but the mechanism remains uncertain.