Anti submarine warfare

As submarines became a more common sight on the marine battlefield, nations around the world increased the amount of time and money they dedicated to developing anti-submarine warfare (ASW). This took two main forms: guarding against submarine damage and actively seeking to damage or destroy enemy submarines.

Science played a huge part in the battle against submarines, requiring technology such as sonar for the locating and tracking of subs, and the development of specialised weapons for defeating them. Throughout World War One, while submarines and ASW technology was still in its infancy, much of the focus of enemy nations was put on defending their fleets and merchant ships from attacks from British submarines. This resulted in the development of escorted convoys, which helped to break the Royal Navy’s hold on supplies. However, major ASW developments all occurred later during World War two.

During WW2, German submarines, known as U-boats, had a huge impact on British merchant shipping - 2.6 million tons was lost in 1940 alone - until 1943 when ASW was finally advanced enough to turn the tide. In fact, by 1944, the Battle of the Atlantic had been won and the U-boats had been defeated.

One of the greatest ASW developments were in the areas of sonar (ASDIC) and depth charges. Sonar was one of the most effective advancements, remove the ability of enemy submarines to remain invisible under the cloak of darkness. And, in fact, when this sonar was fitted onto advanced warships the U-boats became the hunted rather than the hunters.

An early version of the ASDIC had been used during World War One. However, this was only capable of releasing a single impulse, which determined how far away an enemy boat was from the sonar. However, the modern version sent out three impulses at a time, so it was also able to establish the vessel’s depth. This technology did still have its issues; when depth charges were dropped off the back of the Allied boat, the U-boat signal would be lost and could effectively disappear. This was countered by sending a spread of depth charges, which were later launched from the front of the ship as a ‘Hedgehog’ (24 small depth charges) or a ‘Squid’ (three charges). When when the charges missed, they often forced the U-boat to the surface.