Anti-submarine warfare
Anti-submarine warfare (ASW, or in the older form A/S) 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.
Successful ASW operations typically involved a combination of sensor and weapon technologies, along with effective deployment strategies and sufficiently trained personnel. Typically, sophisticated sonar equipment is used for first detecting, then classifying, locating, and tracking a target submarine. Sensors are therefore a key element of ASW. Common weapons for attacking submarines include torpedoes and naval mines, which can both be launched from an array of air, surface, and underwater platforms. ASW capabilities are often considered of significant strategic importance, particularly following provocative instances of unrestricted submarine warfare and the introduction of submarine-launched ballistic missiles, which greatly increased the lethality of submarines.
At the beginning of the twentieth century, ASW techniques and submarines themselves were primitive. During the First World War, submarines deployed by Imperial Germany proved themselves to be a capable threat to shipping, being capable of striking targets even out in the North Atlantic Ocean. Accordingly, multiple nations embarked on research into devising more capable ASW methods, resulting in the introduction of practical depth charges and advances in sonar technology; the adoption of the convoy system also proved to be a decisive tactic. After a lull in progress during the interwar period, the Second World War would see submarine warfare and ASW alike advance rapidly, particularly during the critical Battle of the Atlantic, during which Axis submarines sought to prevent Britain from effectively importing supplies. Techniques such as the Wolfpack achieved initial success, but became increasingly costly as more capable ASW aircraft were introduced. Technologies such as the Naxos radar detector gained only a temporary reprieve until detection apparatus advanced yet again. Intelligence efforts, such as Ultra, had also played a major role in curtailing the submarine threat and guiding ASW efforts towards greater success.
During the postwar era, ASW continued to advance, as the arrival of nuclear submarines had rendered some traditional techniques less effective. The superpowers of the era constructed sizable submarine fleets, many of which were armed with nuclear weapons; in response to the heightened threat posed by such vessels, various nations chose to expand their ASW capabilities. Helicopters, capable of operating from almost any warship and equipped with ASW apparatus, became commonplace during the 1960s. Increasingly capable fixed-wing maritime patrol aircraft were also widely used, capable of covering vast areas of ocean. The Magnetic Anomaly Detector (MAD), diesel exhaust sniffers, sonobuoys and other electronic warfare technologies also became a staple of ASW efforts. Dedicated attack submarines, purpose-built to track down and destroy other submarines, became a key component as well. Torpedo carrying missiles, such as ASROC and Ikara, were another area of advancement.
History[edit]
Origins[edit]
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 was then referred to as a torpedo.[1][2] Even so, various attempts to produce submarines had been made prior to this. In 1866, British engineer Robert Whitehead invented the first effective self-propelled torpedo, the eponymous Whitehead torpedo; French and German inventions followed soon thereafter.[3][4] The first submarine with a torpedo was Nordenfelt I built in 1884–1885, though it had been proposed earlier. By the outbreak of the Russo-Japanese War, all the large navies except the Germans had acquired submarines. Nevertheless, by 1904, all powers still defined the submarine as an experimental vessel and did not put it into operational use.[5]
There were no means to detect submerged U-boats, and attacks on them were limited at first to efforts to damage their periscopes with hammers.[6] The Royal Navy torpedo establishment, HMS Vernon, studied explosive grapnel sweeps; these sank four or five U-boats in the First World War.[7] A similar approach featured a string of 70 lb (32 kg) charges on a floating cable, fired electrically; an unimpressed Admiral Edward Evans considered any U-boat sunk by it deserved to be.[7]
Another primitive technique of attacking submarines was the dropping of 18.5 lb (8.4 kg) hand-thrown guncotton bombs.[8] 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.[7] Firing Lyddite shells, or using trench mortars, was tried.[7] Use of nets to ensnare U-boats was also examined, as was a destroyer, HMS Starfish, fitted with a spar torpedo.[8] 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.[9] Problems with the lanyards tangling and failing to function led to the development of a chemical pellet trigger as the Type B.[9] These were effective at a distance of around 20 ft (6.1 m).[9]
Perhaps the best early 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 also a potential hazard to the dropping ship.[9]