Anti-submarine Warfare - History

History

The first attacks on a ship by an underwater vehicle are generally believed to have been during the American Revolutionary War, using what would now be called a naval mine but what then was called a torpedo, though various attempts to build submarines had been made before this. The first self-propelled torpedo was invented in 1863 and launched from surface craft. The first submarine with a torpedo was Nordenfelt I built in 1884-1885, though it had been proposed earlier. In the Russo-Japanese War of 1904-5, the submarine was a significant threat. By the start of the First World War nearly 300 submarines were in service. Some warships were fitted with an armoured belt as protection against torpedoes.

There were, however, no means to detect submerged U-boats, and attacks on them were limited at first to efforts to damage their periscopes with hammers. The Royal Navy torpedo establishment, HMS Vernon, studied explosive grapnel sweeps; these sank four or five U-boats in the First World War. A similar approach featured a string of 70 lb (32 kg) charges on a floating cable, fired electrically; an unimpressed Louis Mountbatten considered any U-boat sunk by it deserved to be.

Also tried were dropping 18.5 lb (8.4 kg) hand-thrown guncotton bombs. The Lance Bomb was developed, also; this featured a 35–40 lb (16–18 kg) cone-shaped steel drum on a 5 ft (1.5 m) shaft, intended to be thrown at a submarine. Firing Lyddite shells, or using trench mortars, was tried. Use of nets to ensnare U-boats was also examined, as was a destroyer, HMS Starfish, fitted with a spar torpedo. To attack at set depths, aircraft bombs were attached to lanyards which would trigger their charges; a similar idea was a 16 lb (7.3 kg) guncotton charge in a lanyarded can; two of these lashed together became known as the Depth Charge Type A. Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the Type B. These were effective at a distance of around 20 ft (6.1 m).

The best concept arose in a 1913 RN Torpedo School report, describing a device intended for countermining, a "dropping mine". At Admiral John Jellicoe's request, the standard Mark II mine was fitted with a hydrostatic pistol (developed in 1914 by Thomas Firth & Sons of Sheffield) preset for 45 ft (14 m) firing, to be launched from a stern platform. Weighing 1,150 lb (520 kg), and effective at 100 ft (30 m), the "cruiser mine" was a potential hazard to the dropping ship, but was also on the right track.