Hedgehog (weapon)

Hedgehog (weapon). The Hedgehog was a forward-throwing anti-submarine weapon developed by the United Kingdom during the Second World War. It fired a pattern of 24 contact-fuzed spigot mortars ahead of an attacking ship, improving upon the limitations of depth charge attacks. The system saw extensive service with Allied navies and remained in use for decades, representing a major advance in anti-submarine warfare tactics and technology.

Design and operation

The weapon consisted of a multi-barreled spigot mortar assembly mounted on the forecastle of a warship, such as a destroyer or frigate. It projected a circular pattern of 24 projectiles, each weighing approximately 65 pounds and containing a 35-pound Torpex high explosive charge, to a distance of about 200–250 yards ahead of the ship. Unlike depth charges, which used hydrostatic pistols, the Hedgehog's munitions were fitted with contact fuzes that detonated only upon direct impact with a submarine's hull. This design required a more accurate prediction of a U-boat's position but eliminated the prolonged waiting period for depth charges to sink and the resultant loss of sonar contact due to explosion turbulence. The launcher was typically controlled from the ship's ASDIC (sonar) hut, with firing solutions calculated to place the elliptical pattern over the predicted location of the target.

Development and history

The Hedgehog was developed under the auspices of the British Directorate of Miscellaneous Weapons Development (DMWD), often called "Wheezers and Dodgers," in response to the severe threat posed by the German U-boat campaign. Key figures in its development included Millis Jefferis and Charles Goodeve. The initial concept sought to overcome the ineffectiveness of stern-dropped depth charges, which allowed a submarine time to maneuver after an attacking ship passed overhead. The first successful test was conducted in 1941 aboard the HMS *Westcott*, and the system entered full service with the Royal Navy in early 1942. Its adoption was accelerated by the support of prominent naval commanders like Admiral Sir Max Horton, who commanded Western Approaches Command.

Deployment and use

The Hedgehog was widely deployed aboard Allied escort vessels from 1942 onward, including ships of the Royal Canadian Navy and the United States Navy. It became a standard fixture on Captain-class frigates, River-class frigates, and numerous destroyer escorts. Its first confirmed combat success was by the HMS *Fame* in 1942. The weapon was employed extensively during the climactic convoy battles of 1943, such as those surrounding Convoy ONS 5 and Convoy SC 130. The United States Coast Guard cutter *Spencer* also used it to sink U-175 in 1943. Its use required close coordination between the ship's commander, ASDIC operators, and the Hedgehog crew to achieve a successful interception.

Effectiveness and impact

While initially suffering a high rate of non-success due to the demanding accuracy required, the Hedgehog's kill probability per attack rose significantly as sonar operators and tactics improved. It was credited with sinking approximately 50 U-boats during the war. The weapon's psychological impact was considerable, as a submarine crew would hear the projectiles striking their hull moments before the devastating explosion, with no warning from earlier detonations. The Hedgehog helped shift tactical advantage to escort groups, contributing to the defeat of the Kriegsmarine's submarine force by 1944. Its success directly influenced postwar anti-submarine warfare developments, including the Squid mortar and later Limbo system.

Variants and derivatives

The original Mark 10 Hedgehog was followed by the Mark 11, which had a rectangular, trainable launcher. The United States Navy produced its own variant, the **Mk 15**, used on many DEs and DDs. A simplified, lightweight version for smaller vessels was developed as the **"Hedgehog Mk 3"** or **"Porcupine"**. The fundamental spigot mortar principle was later scaled up into the **"Mousetrap"** weapon for American PT boats and coastal craft. The most direct successor was the British three-barreled **Squid** mortar, which fired larger, depth-fuzed projectiles astern, and the subsequent Limbo system, which remained in service with the Royal Navy into the 1990s.

Category:Anti-submarine weapons Category:World War II naval weapons Category:Naval weapons of the United Kingdom Category:Mortars (weapon)