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Anti-submarine mortars are artillery pieces deployed on ships for the purpose of sinking submarines by a direct hit with a small explosive charge. They are often larger versions of the mortar used by infantry and fire a projectile in relatively the same manner. They were created during World War II as a development of the depth charge and work on the same principle.
Anti-submarine warfare did not become an issue of great concern until World War I, when Germany used submarines in an attempt to strangle British shipping in the Atlantic Ocean and elsewhere. The earliest way to counter a submarine was in the form of depth charges, which were large canisters filled with explosives, rolled off the back of a ship and detonated by a hydrostatic fuze. Depth charges served well throughout World War I but were not without flaws. A ship had to pass directly over a submarine to score an effective hit, and as such, depth charges were dropped in lines instead of more effective clusters and could only be carried in ships fast enough to avoid the concussion of the explosion. The depth charges were also not as effective as one might think at sinking a submarine - only a very close detonation would sink a submarine, and the problems of scoring a direct hit meant that a submarine was more often damaged than destroyed by depth charges.
After World War I depth charge throwers were developed, which could hurl depth charges some 100 feet (30 m) from the side of a ship, perpendicular to its direction of travel. These were a significant improvement over the old method, permitting the use of large 'patterns' of up to ten depth charges from the throwers and stern depth charge rails used together. However, they still required a ship to pass very close to a submarine, which entailed a loss of sonar (ASDIC) contact during the final stages of the approach. Submarines could and did use this period to take evasive action.
It was the British who developed the first anti-submarine mortars. Several versions appeared in 1917, most notably the BL 7.5-inch naval howitzer. However, the anti-submarine mortar did not become a truly successful weapon until the advent of the multi-barrelled Hedgehog 25 years later.
During World War II, submarines once again posed a major threat to Allied shipping, which necessitated the development of more effective anti-submarine mortars. These all had the common characteristic of throwing multiple charges ahead of the attacking vessel while it was still in sonar contact with a submarine. The most successful was the Hedgehog, which consisted of 24 small spigot mortar rounds, each one 7 inches (180 mm) in diameter and weighing 65 pounds (29 kg) with a 35-pound (16 kg) warhead. Each projectile had a range of about 250 yards (230 m) and was fired in a circular pattern in front of a ship. While the warhead on a Hedgehog was much smaller than that of a depth charge, it scored three times as many kills than its predecessors. This was due to the use of a contact fuze on the projectile, which would only detonate on impact with a target. Since the projectile would only explode on a hit, the long periods of sonar "blackout" from the blast and turbulence of a conventional depth charge explosion were eliminated. In the later stages of World War II, the Hedgehog was complemented in British service by the Squid three-barrelled depth charge mortar, which fired 390 lb (180 kg) depth charges to a range of 270 yd (250 m). [1]
The homing torpedo and anti-submarine rocket largely replaced the anti-submarine mortar in naval combat. The British Limbo system, with three gyro-stabilized barrels, fires 350-pound (160 kg) projectiles to a range of 1,000 yards (910 m). It remained in service with many British and Commonwealth navies until the 1980s. The Italian Menon system, introduced in 1956, was used until their retirement in the 1980s. The Elma ASW-600 anti-submarine mortar, developed by Sweden in the 1980s, is the latest weapon of the type and is still in limited use.
A depth charge is an anti-submarine warfare (ASW) weapon designed to destroy submarines by detonating in the water near the target and subjecting it to a destructive hydraulic shock. Most depth charges use high explosives with a fuze set to detonate the charge, typically at a specific depth from the surface. Depth charges can be dropped by ships, patrol aircraft and helicopters.
The Hedgehog was a forward-throwing anti-submarine weapon that was used primarily during the Second World War. The device, which was developed by the Royal Navy, fired up to 24 spigot mortars ahead of a ship when attacking a U-boat. It was deployed on convoy escort warships such as destroyers and corvettes to supplement the depth charges.
Squid was a British World War II ship-mounted anti-submarine weapon. It consisted of a three-barrelled mortar which launched depth charges. It replaced the Hedgehog system, and was in turn replaced by the Limbo system.
An anti-submarine weapon (ASW) is any one of a number of devices that are intended to act against a submarine and its crew, to destroy (sink) the vessel or reduce its capability as a weapon of war. In its simplest sense, an anti-submarine weapon is usually a projectile, missile or bomb that is optimized to destroy submarines.
This article explains terms used for the British Armed Forces' ordnance (weapons) and ammunition. The terms may have different meanings depending on its usage in another country's military.
Limbo, or Anti Submarine Mortar Mark 10, was the final development of the forward-throwing anti-submarine weapon Squid, designed during the Second World War and was developed by the Admiralty Underwater Weapons Establishment in the 1950s.
Mousetrap was an anti-submarine rocket launcher used mainly during World War II by the United States Navy and Coast Guard. Its development began in 1941 as a replacement for Hedgehog anti-submarine mortar. Those were spigot-launched, which placed considerable strain on the launching vessel's deck, whereas Mousetrap was rocket-propelled. As a result, Mousetrap's four or eight rails for 7.2-inch (183 mm) rockets saved weight and were easier to install.
Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, submarines, or other platforms, to find, track, and deter, damage, or destroy enemy submarines. Such operations are typically carried out to protect friendly shipping and coastal facilities from submarine attacks and to overcome blockades.
An anti-submarine missile is a standoff anti-submarine weapon, often a specialized variant of anti-ship missile. Anti-submarine missile usually include a jet or rocket engine and a warhead aimed directly at a submarine. In these missiles, a torpedo or a depth charge is used as a warhead. The anti-submarine missile can be either a cruise missile or a ballistic missile.
The Mackenzie-class destroyer was a class of warship used by the Royal Canadian Navy and Canadian Forces from the 1960s–1990s. Six such ships were envisioned, of which four were completed to this specification. The last two hulls were completed to the post DDH conversion St. Laurent-class design ; they were designated as the Annapolis class instead. The four Mackenzie-class destroyers spent most of their service in the Pacific Ocean, used primarily in a training role. Their only significant update was the DELEX program, which was completed between 1982 and 1985 and updated their navigational radar and their sonar.
HMCS St. Thomas was a Castle-class corvette of the Royal Canadian Navy. She served during the Second World War in the Battle of the Atlantic, taking part in the sinking of the German U-boat U-877 in 1944. Initially ordered by the British Royal Navy as Sandgate Castle, the ship was transferred to Canada before completion. Following the war, the corvette was converted for mercantile use and renamed Camosun III, then Chilcotin and Yukon Star in 1958 before being broken up in Washington in 1974.
The Dealey-class destroyer escorts were the first post-World War II escort ships built for the United States Navy.
The Fairlie Mortar was an unsuccessful British anti-submarine mortar design of the early second World War. It projected small anti-submarine bombs simultaneously, ten from each side of the ship's forecastle, each containing 20 lb (9.1 kg) of explosive. The Fairlie Mortar was not a success and 'Hedgehog', a spigot mortar projecting 24 small bombs from a platform, eventually became the predominant British ship-borne anti-submarine weapon in the war.
HMS Hever Castle was a Castle-class corvette constructed for the British Royal Navy in the Second World War. Transferred to the Royal Canadian Navy before completion, the ship was renamed HMCS Copper Cliff and saw service as a convoy escort for the remainder of the war. Following the war, the vessel was sold for mercantile use and renamed Ta Lung, operating under a Chinese flag. In 1949, the ship was taken over by the Communist Chinese government, rearmed and renamed Wan Lee.
HMCS Hespeler was a Castle-class corvette of the Royal Canadian Navy which served during the Second World War as a convoy escort that was originally ordered as HMS Guildford Castle for the British Royal Navy but before completion was transferred and renamed. Following the war, the ship was sold for mercantile use, renamed Chilcotin in 1946, Capri in 1958, Stella Maris in 1960, and Westar in 1965. The ship was destroyed by fire in 1966 while at Sarroch, Sardinia. The hulk was taken to La Spezia, Italy where Westar was broken up.
HMS Sherborne Castle was a Castle-class corvette constructed for the Royal Navy during the Second World War. Before completion, the ship was transferred to the Royal Canadian Navy and renamed HMCS Petrolia. During the war Petrolia saw service as a convoy escort. Following the war, the corvette was sold for mercantile use and renamed Maid of Athens in 1946 and in 1947, renamed Bharat Laxmi. The ship remained in service until 1965 when Bharat Laxmi was sold for breaking up.
HMS Pembroke Castle was a Castle-class corvette built for the British Royal Navy during the Second World War. Before completion, the ship was transferred to the Royal Canadian Navy and renamed HMCS Tillsonburg. Tillsonburg saw service as a convoy escort during the Second World War in the Battle of the Atlantic. Following the war, the corvette was converted for merchant use and sold to Chinese interests. The ship was renamed Ta Ting in 1946, Chiu Chin in 1947 before being taken over the Nationalist Chinese government in 1951, rearmed and renamed Kao An. The ship remained in service with the Republic of China Navy until being discarded in 1963.
The Mark VII depth charge was the standard British depth charge for the first three years of World War II
An anti-submarine rocket is an anti-submarine weapon type deployed on surface warships for the purpose of sinking or damaging submarines by small explosive charges. They are similar to anti-submarine mortar but a comparably more modern system. This type of weapon used rockets instead of spigot mortars to deliver the explosive.