They Called It a 'Mine' to Hide Its Secret — It Sank 37 U Boats Without Missing

Hidden H

May 12, 1943. North Atlantic. An RAF Liberator spots a German U-boat on the surface. The submarine crash-dives. But instead of dropping blind depth charges, the pilot releases something new. A short, fat torpedo that can hear. It's called FIDO. Built from telephone switchboard parts, powered by a