The torpedo was invented by Englishman John Whitehead for the Austro-Hungarian navy in 1866, but those in use by 1939 were far more capable than his 7-knot, flywheel-driven weapon. However, except for Japan, no nation entered World War II with torpedoes that differed significantly from those of World War I. All were straight running and had the same top speeds (39–47 knots), ranges (2,500–7,000 yds), and depth-setting mechanisms as those of the earlier war. A few countries had influence warheads that were expected to detonate as they passed under the ship's hull, thereby breaking its back, but those weapons proved unreliable in early operations and had to be withdrawn until their technical faults were corrected. However, by war's end, the most advanced torpedoes had homing guidance and a complex variety of influence warheads, and more important, they had become the critical weapon of war between naval forces on and above the surface and those below.
Employed mostly by submarines, torpedoes were responsible for more than 30 percent of the warship losses and 70 percent of merchant shipping losses during the war. Those statistics are rather ironic, given that, before the war, submarines were not expected to play a significant role in naval operations and that the three naval powers that employed torpedoes most effectively suffered torpedo reliability problems during the war's early years. U.S. and German difficulties with their weapons' warheads, depth-setting mechanisms, and guidance systems are the best known, but Great Britain suffered similar problems with its own torpedoes. However, the Royal Navy accepted the fleet's reports and corrected the technical faults within nine weeks of receiving the first report. The United States and Germany waited nearly a year to examine their problems, and another year passed before they corrected their weapons' deficiencies. Nonetheless, those two countries best demonstrated the deadly effectiveness of the submarine-torpedo combination in naval warfare. In fact, Germany and the United States possessed the most technologically advanced torpedoes at war's end, with the former having the best antiship torpedo and the latter the world's only antisubmarine torpedo, designated the Mark 24 "mine" to hide its true nature.
For its part, Japan entered the war with the only torpedoes that were significantly better than those used in World War I. Japanese submarine and ship torpedoes employed an oxygen-alcohol power train that gave their torpedoes a speed of almost 50 knots and a range exceeding 42,000 yds, with little wake. They also had the war's most powerful warheads (weighing more than 1,000 lbs) and were extremely reliable, providing Japan's highly trained crews with a critical advantage in ship-to-ship and submarine-to-ship engagements.
Japan, however, wasted that technological advantage by not employing the torpedoes' most effective platform, the submarine, effectively. Moreover, unlike Germany, Japan never developed a homing system to guide their torpedoes toward a ship's engine noises or wake, which reduced the probability of their hitting a distant maneuvering target. More important, by 1943, naval airpower and air defenses including radar had increased engagement ranges to the point that submarines became the torpedo's only tactically viable weapons platform, rendering Japan's advantage in torpedo range all but irrelevant. Indeed, antiship torpedoes diminished in importance as ship and aircraft weapons from that year and have been supplanted on those platforms by antisubmarine torpedoes since the early 1950s.
France entered the war with torpedoes that were obsolescent by World War II standards, and the nation was defeated by Germany before newer models could be developed. The Soviet Union and Italy also suffered from a lack of torpedo research and development. All three nations were slow to make the change from the 45 cm (18-inch) torpedoes for surface ships and submarines to the 533 mm (21-inch) torpedoes adopted by most other nations, whereas Japan had gone to 61 cm (24-inch) torpedoes (but only in surface ships, for Japanese submarines used the 21-inch oxygen-driven torpedo). However, Soviet and Italian torpedoes were simple and reliable. In fact, Italy's aircraft-carried torpedoes were so much better than those of Germany that Luftwaffe antishipping squadrons preferred to use Italian models rather than their own.
Many of the minor navies still employed the smaller and older torpedoes on their ships and submarines, but 45 cm torpedoes were carried primarily by aircraft until 1943, when they also began to carry the larger 533 mm models.
Much has been written about the revolutionary changes torpedoes underwent in the course of the war. Most of this transformation was driven by the Battle of the Atlantic between the Western Allies and the German Kriegsmarine (navy), where torpedo and antisubmarine-detection systems shaped the course of the battles.
Denied heavy weapons by the Versailles Treaty, post–World War I Germany's naval doctrine underemphasized torpedo engagements. This situation changed when Adolf Hitler rose to power and, with the navy under Admiral Erich Raeder, sought to build a large, conventional German naval force capable of challenging Britain on the seas. Partly as a result of this concentration, there were no new designs or concepts in torpedo warfare before the U-boat arm's effectiveness became essential to Germany's war effort after 1940. By 1942, however, Germany had homing torpedoes that guided onto the target ship's engine noises and pattern-running torpedoes that made evasion difficult. Research programs included wake-homing, active sonar-based terminal guidance, and even a rocket-propelled high-speed torpedo, which, however, never got past the drawing board.
Fortunately for the Allies, Germany's research and development effort lacked direction before Admiral Karl Dönitz took command of the Kriegsmarine in January 1943. As torpedoes proved critical to the German U-boat arm, so, too, did they figure in the Western Allies' struggle against the U-boat. The Allies developed search and guidance systems for torpedoes to attack maneuvering underwater submarines. The Mark 24 "mine" employed from Allied antisubmarine aircraft used a descending circular search and "passive acoustic homing" guidance to seek, find, and attack submerged German submarines by detecting and following the noises made by the U-boats' machinery. The Mark 24 was the precursor to modern antisubmarine torpedoes, as was the German homing torpedo, father to the antiship torpedoes carried by today's submarines. Carl O. Schuster
Campbell, John. Naval Weapons of World War II. Annapolis, MD: Naval Institute Press, 1985.; Ellis, John. The World War II Databook: The Essential Facts and Figures for All the Combatants. London: Aurum Press, 1993.; Grey, Edwyn. The Devil's Device: Robert Whitehead and the History of the Torpedo. Rev. ed. Annapolis, MD: Naval Institute Press, 1991.; Hough, Richard. Naval Battles of the Twentieth Century. Woodstock, NY: Overlook Press, 1999.; Miller, Nathan. War at Sea. New York: Oxford University Press, 1995.; Van der Vat, Dan. The Atlantic Campaign: World War II's Great Struggle at Sea. New York: Harper and Row, 1988.
Carl O. Schuster