Depth Charge

The depth charge is an anti-submarine weapon consisting of a drum or canister of explosive dropped from a ship's stern or thrown by a projector to a set depth, where a hydrostatic fuse detonates it, the surrounding water transmitting a lethal shock wave to any submarine within the charge's effective radius even without a direct hit. Introduced by the Royal Navy in 1916 during the First World War in response to the growing threat of German U-boats, depth charges became the primary anti-submarine weapon of both World Wars, dropped in patterns from escort ships working with sonar, later called ASDIC by the British, to localize a submerged submarine before attacking. Depth charge tactics and equipment steadily improved through the Second World War's Battle of the Atlantic, and though later replaced in most frontline roles by homing torpedoes and guided anti-submarine rockets, the basic depth charge concept remains in limited use by some navies today.