Who has not seen Das Boot or Run Silent, Run Deep, or read the novels on which these films are based, without shuddering at the thought of being encased in a sub hull below the ocean waves subjected to a prolonged depth charge attack? Depth charges are almost synonymous with being the warship’s anti-submarine weapon for use against submerged boats.

However, depth charges, first frequently used in World War I, had a major defect. The massive explosions that so affected morale, positively on the surface and negatively below, also meant that sonar contact, the only means of detecting submerged subs, was lost unless damage from the target was soon apparent on the surface. The detection system and the weapon system for attacking submerged opponents were not complementary.

The Canadian navy expanded from 13 to 375 warships during the Second World War, the majority of which were anti submarine vessels built in Canada. For attacking submerged subs, these warships were equipped with rail launchers of prewar design that dropped Mark VII depth charges, also of prewar design, over the stern. This approach required the attacking surface ship to pass over the submerged target, usually at best speed, at which point maintaining sonar contact was impossible even before the depth charges actually exploded.

The Mark II launcher, designed in the First War, was fitted to all RCN minesweepers, corvettes, frigates and destroyers. This thrower fired depth charges complete with their cradles at an angle of 90 degrees to the ship’s course. The Mark IV launcher, which kept the cradle, making reloads easier, was later fitted to all destroyers, River class frigates, and the twelve British-built Castle class corvettes that the RCN also used.

After a German U-boat was captured, it was discovered that German submarines could dive to 600 feet, forcing an improvement in the Mark VII depth charge. In addition, a special heavy Mark VII with attached weights was also developed. Canadian River class destroyers, such as the original HMCS Ottawa, launched even heavier Mark X depth charges from their torpedo tubes.

The first workable alternative to dropping explosives astern or throwing them to the side came from a Canadian mind, Charles Goodeve, a native of Neepawa and a graduate in science from the University of Manitoba, and subsequently University College in London. He first joined the RCNVR at Winnipeg’s newly established Reserve Division and continued in the RNVR, obtaining a great variety of experience on submarines, minesweepers, destroyers and even battleships.

In 1939, Lieutenant Commander Goodve was appointed to the British naval establishment dealing with mines. His first achievements were related to developing counter measures against German magnetic mines of which the L-sweep and the development of degaussing are the best known.

Goodve’s achievement in the case of anti-submarine warfare was the introduction into service, albeit apparently grudgingly in both the RN and RCN, of the first ahead throwing ASW weapon. The hedgehog system threw 24 smaller projectiles 215 yards ahead of the attacking surface vessel in a 130-foot diameter circle. Sonar contact could be maintained right up to time of attack – because hedgehogs were contact fused, they only exploded on hitting the submarine.

By the end of 1941 RN ships were being equipped with hedgehogs, although not in time to avert the terrible period of January to June 1942 when 400 Allied ships were sunk for the loss of only seven U-boats. It took time for escort crews to realize that the best attack approach required slowing down, not speeding up, and to practice using this new weapon. Ironically, the slowness demanded by hedgehog attacks was the best speed for countering the newly introduced German acoustic torpedoes designed to give subs a counter escort weapon.

An improved system was introduced in 1944, the so-called squid, which fired from a mortar-like system that could be rotated through 90 degrees and integrated with the ship’s sonar to control firings. The bombs were hydrostatically fused, unlike hedgehogs, but this time directed by the sonar, rather than hand set like depth charges.

In the RCN, only the British built Castle class corvette was equipped with the squid during the Battle of the Atlantic, although the postwar Canadian navy utilized this ASW weapon system until 1967. (One of the books reviewed in Sep/Oct 07 outlines the political fallout from perceptions of how slowly the RCN adapted.)

The development and introduction into service of Goodeve’s hedgehog system, and its immediate successor, the squid, as a departure from First War technology, enabling closer integration of detection with the weapons for attacking submerged submarines, serves as a study in absorption of new equipment to solve longstanding tactical problems in time of war.