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H-008-3: Torpedo Versus Torpedo 

H-Gram 008 Attachment 3
Samuel J. Cox, Director NHHC
July 2017

In 1940, a Japanese “walk-in” source provided the U.S. naval attaché in Tokyo with information on the Japanese Type 93 “oxygen torpedo” (known after the war as “Long Lance”). The Type 93 had a much longer range, was faster, and had a larger warhead than any other known torpedo in the world. The Office of Naval Intelligence (ONI) provided this intelligence, from an “impeccable source,” to the Navy Bureau of Ordnance, which evaluated and dismissed the report in the belief that the Japanese could not have developed a torpedo more advanced than our own, and that the use of compressed oxygen as an oxidizer was too dangerous. Seven U.S. Navy cruisers, nine destroyers, the abandoned aircraft carrier Hornet (CV-8), and additional Allied ships were sunk by Type 93 torpedoes during World War II (over 3,100 U.S. Sailors killed), in most cases when the target ships, believing themselves to be safely out of torpedo range, were hit by surprise. The Type 93 and other Japanese torpedoes were reliable; U.S. torpedoes were not, despite being more “sophisticated.”

U.S. Mark 14 Submarine Torpedo

At the start of World War II, the newest operational U.S. torpedoes were the Mark 13 air-launched torpedo, the Mark 14 submarine-launched torpedo, and the Mark 15 surface-launched torpedo. Although each torpedo was different, each version had significant components in common, particularly the Mark 6 magnetic influence exploder (on the Mark 14 and 15.) As passive anti-torpedo defenses of capital ship designs significantly improved as a result of World War I experience, the United States sought to overcome increased armor, water-tight compartmentation, anti-torpedo blisters, and other features by designing a torpedo that would pass underneath the target ship and detonate several feet below the keel using magnetic influence (similar to modern torpedoes.) The Japanese approach to the same problem was to build a bigger and faster contact torpedo with a huge warhead. 

U.S. submarine skippers were the first to realize that U.S. torpedoes had major problems, and they found out the hard way as a result of failed attacks. The skipper of Sargo (SS-188) fired 12 torpedoes on 24 December 19 41 at four targets—the last four torpedoes with textbook perfect set-up—and none hit. Seadragon (SS-194) fired eight torpedoes on her first war patrol in January 1942 for only one hit. Numerous other submarine commanders experienced the same problem. Even the great Lieutenant Commander  Dudley “Mush” Morton on Wahoo (SS-238) came back empty-handed from a patrol in May 1943 due to faulty torpedoes. On 9 April 1943, the skipper of Tunney (SS-282,) Lieutenant Commander John A. Scott, had probably the most frustrating day in the history of the U.S. submarine force, with perfect short-range shots at three Japanese aircraft carriers (Junyo, Hiyo, and Taiyo,) firing all ten tubes without a single hit.

The initial response from the Bureau of Ordnance (BuOrd) was to blame the submarine skippers (“operator error”) because the torpedoes had worked fine in pre-war tests. Actually, they hadn’t. Because of the expense of torpedoes (about $160K in today’s dollars), BuOrd’s limited budget, and inability of the U.S. industrial base to produce anywhere near enough of the torpedoes required, the U.S. Navy conducted no tests before the war using production torpedoes against an actual target. (The Japanese conducted extensive live-fire tests against target ships.) All U.S. tests used exercise warheads, with an upward looking camera substituting for the magnetic influence sensor, and since the exercise torpedoes passed under the target ships—as they were supposed to—the tests were deemed a success.

The Mark 14 had several serious flaws, which masked each other. The first flaw detected was that war shots ran about 10 feet deeper than set. Shortly after assuming command of Southwest Pacific Submarines in June 42, Rear Admiral Charles Lockwood ordered a series of tests with submarines firing torpedoes into nets that conclusively proved that the torpedoes were running too deep. By then, Pacific Fleet submarines had fired over 800 torpedoes (a year’s worth of production at that time) with very little to show for it. When news of the tests reached CNO Ernest J. King, he turned his famous wrath on BuOrd, which, however, did not save a number of submarine skippers who had been relieved of command for supposedly being incompetent or not aggressive enough (in some cases true, but they certainly were not helped by torpedoes that didn’t work).

Once the Mark 14 depth-control issue was recognized, many submarine skippers set their run depths to “zero,” which increased the chance of a torpedo broaching. However, even when the torpedoes ran at an appropriate depth, the number of premature detonations and duds greatly increased. This is actually what happened to Scott on Tunney: seven of the ten torpedoes he fired at the three Japanese carriers would have been hits except that they exploded prematurely, resulting in only light damage to one carrier. As submarine skippers began to suspect the Mark 6 exploder, nearly all requested permission to deactivate this component, which was denied. As a result, some skippers deactivated the exploders anyway, and in their post-patrol reports inflated the estimated tonnage of their targets to justify expending more torpedoes per target. After he became Commander Submarine Force Pacific, Rear Admiral Lockwood used reports from submarine skippers, as well as intercepted and decoded Japanese radio reports that documented premature explosions, to request permission from Admiral Nimitz to deactivate the magnetic exploders, which Nimitz promptly granted. Deactivation was ordered on 24 June  1943.

The deactivation of the magnetic exploders solved the premature detonation problem, but revealed that the contact exploder had major design flaws as well, resulting in more duds. Lieutenant Commander Dan Daspit of Tinosa (SS-283) returned from a patrol with convincing data that the contact pistol was defective. Lockwood ordered another series of tests (drop tests and even firing torpedoes into cliff faces) that confirmed the detonators were defective. In fact, torpedoes that hit the target at a 90 degree angle (i.e., a perfect shot) were more likely to fail. The interim fix was for submarines to attempt to hit targets at more oblique angles, and this actually did help reduce the dud problem.

The fourth major problem with the Mark 14 was a tendency to run in circles, with the risk to the submarine that fired the torpedo. Although no U.S. subs are known to have been sunk by a circling Mark 14, this problem was never completely solved. In fact, Tang (SS-306,) Lieutenant Commander Richard O’Kane commanding, was sunk on 25 October 1944 by her own circling torpedo, a new Mark 18. Tullibee (SS-284) was sunk by a circular run on 26 Mar 1944, but the type of torpedo is unknown.

By early 1944, with fixes finally implemented, the Mark 14 became a very reliable weapon that inflicted enormous damage to the Japanese navy and merchant marine, but it could have inflicted so much more sooner had adequate budget resources been devoted to realistic testing and training before the war and had there been a more expeditious BuOrd shore establishment effort to fix problems identified by submariners—rather than trying to pass the blame back to the sub skippers.

U.S. Mark 13 Air-Launched Torpedo

Like submariners, U.S. aviators quickly began to suspect that their torpedoes were frequently defective. Dismal results with torpedoes during early carrier raids in the Marshalls and at Tulagi fueled suspicions. Although some torpedoes actually hit the Japanese carrier Shoho at the battle of the Coral Sea —and worked as designed—there were actually significantly fewer hits than claimed, as many bomb near-misses were mistaken for torpedo hits. No torpedoes hit the Japanese carrier Shokaku at Coral Sea, but none of the TBD Devastator torpedo bombers were lost in that attack or during the attack on Shoho, either, giving a false sense to U.S. commanders that the TBD/Mark 13 combination was a viable means of attack. This notion was disabused at Midway when nearly every torpedo bomber was shot down without obtaining a single hit. Some reports claim that even before Midway, Vice Admiral Halsey had been so concerned about the TBD’s lack of effectiveness and vulnerability that he had no intention to use them in future engagements until dive bombers had thoroughly worked over the targets well in advance. Pre-war tactics ideally called for the dive bombers to drop on target just slightly ahead of the torpedo bombers in order to divert fighters and suppress anti-aircraft fire, giving the torpedo bombers a better chance. At Midway, the torpedo bombers reached the Japanese carriers first and paid the price.

Due to high cost and production shortfalls, pre-war exercises with even exercise torpedoes were extremely rare, but even then showed that the Mark 13 was prone to running at errant angles, running on the surface or too deep, or not running at all, even when dropped at very low speeds. In the case of air-dropped torpedoes, the reason for failure was generally because components of the torpedo were damaged upon impact with the water. The TBD-1 Devastator , the U.S. Navy's torpedo bomber at the beginning of World War II, was not very fast to begin with, but additional speed and altitude restrictions meant to improve torpedo reliability made the TBD even more vulnerable to enemy fighters and shipboard anti-aircraft fire. A sad irony is that extensive tests conducted after the battle of Midway concluded that the stringent speed and altitude restrictions were actually counter-productive: The reliability of the torpedo had more to do with the angle it impacted the water than with speed or altitude of drop. The slow speed and low altitude caused the torpedo to hit the water on a very flat trajectory that actually resulted in more component damage.

Extensive tests in late 1942 and 1943 revealed twelve major flaws with the Mark 13 torpedo, which resulted in a dual-track solution of making fixes to the weapon while attempting to simultaneously accelerate the development, with significant technical risk, of the Mark 25 torpedo. The development of shroud rings that reinforced the tail fins (frequently damaged in drops) and drag rings, which slowed the torpedo after drop (allowing the aircraft to maintain higher speeds and higher altitudes, while improving angle of entry into the water), had significant positive impact on Mark 13 reliability. Although Mark 13 torpedo performance remained poor throughout 1943, by mid-1944 performance improved markedly, particularly with the addition of radar to TBF Avenger torpedo bombers that provided a precise range to the target. By 1944, Avengers were able to drop the Mark 13 at altitudes up to 800 feet and at a speed of 260 knots, significantly increasing attack profile flexibility and aircraft survivability.

Nevertheless, because of the torpedo bomber debacle at Midway (and the spectacular success of the dive bombers,) the U.S. Navy skewed carrier air group composition toward more dive bombers and fewer torpedo bombers after Midway. The result was that fewer Japanese ships were sunk than might have otherwise been the case, which was a particular factor in the disappointing number of Japanese ship losses due to air attack at the battle of the Philippine Sea in June 1944. Although Japanese aircraft carriers had design flaws that made them vulnerable to bombs, Japanese surface combatants were very resistant to bomb damage, and numerous ones survived multiple bomb hits to fight another day. Japanese battleships and heavy cruisers were almost impossible to sink with bombs alone, although a cruiser’s torpedo banks were vulnerable. The Japanese super-battleships Musashi and Yamato both absorbed numerous bomb hits and kept on coming; it was improved Mark 13s that sank them (and even then, it took numerous torpedo hits).

U.S. Mark 15 Surface-Launched Torpedo

The Mark 15 torpedo was the standard torpedo employed by U.S. destroyers in World War II, and suffered most of the same problems as the Mark 14 submarine-launched torpedoes. However, it took longer to detect the problems because of fewer opportunities to employ the weapons in the early months of the war. The Mark 15 was designed to have a longer range and larger warhead, which made it longer and heavier than the Mark 14. Despite the differences, the Mark 15 and Mark 14 had numerous components in common, in particular the problematic Mark 6 exploder. Problems with the Mark 15 were not actually solved until after the problems with the Mark 14 were first identified by the submarine community.

U.S. Navy surface torpedo tactics were also seriously flawed, as they were developed in the 1930s without an appreciation for Japanese capabilities. The U.S. Navy War Instructions (FTP-143) stated that U.S. cruisers were to avoid night combat unless conditions were favorable (U.S. cruisers had had their torpedo banks removed to save weight, whereas Japanese cruisers retained theirs). As a result, U.S. cruisers were unprepared for night fighting and suffered severely from Japanese torpedo attacks during the Solomons campaign (which will become apparent in the next H-Gram on Savo Island).  Under FTP-143, U.S. destroyers were to attack first with guns, but to reserve torpedoes for capital ship targets. The typical result was that Japanese ships (which held fire until after launching torpedoes) would fire their longer-range torpedoes at the U.S. gun flashes, and numerous U.S. destroyers were sunk before ever having a chance to employ torpedoes (despite the advantage of having radar). Not until the battle of Vella Gulf in August 1943, after numerous engagements in which U.S. destroyers suffered grievous losses, did U.S. Navy destroyers finally successfully execute a surprise night torpedo attack against a Japanese force. Even at the night battle of Surigao Strait in October 1944 (which was a debacle for the Japanese), the number of hits obtained by U.S. torpedoes relative to the number fired was dismally low.

Japanese Type 93 Sanso Gyorai “Oxygen Torpedo” (“Long Lance”)

The term “Long Lance” was coined by U.S. Navy historian Rear Admiral Samuel Eliot Morison after World War II, so was not used during the war.

From the early 1920s, the Japanese understood that their battle line would always be outnumbered by the U.S. fleet, initially due to the limitations of the Washington and London naval treaties, but also because senior Japanese naval leaders did have an understanding of, and respect for, U.S. industrial and ship-building capacity. The Japanese expected a war with the United States to unfold in almost the same manner as the U.S. Navy did in War Plan Orange, specifically that the U.S. battle fleet would work its way across the Pacific to a climactic Mahanian duel of battle lines in waters near Japan. Realizing their disadvantage, the Japanese embarked on an extensive effort to develop an asymmetric advantage (long before anyone came up with that term) to attrite the U.S. fleet as it came across the Pacific so that the odds would be more even for the great surface battle. The Japanese solution of choice was the night torpedo attack. 

Throughout the pre-war years, the Japanese invested enormous resources in developing night torpedo attack capability, including extensive realistic nighttime training—despite the inherent dangers. By contrast, the U.S. severely curtailed realistic night training after the Point Honda disaster in September 1923, when seven destroyers ran aground at night at high speed doing exactly that kind of training (I will cover the Point Honda disaster in a future H-Gram). The Japanese invested heavily in improved night optics, searchlights, pyrotechnics, night-scouting flights by cruiser-embarked float planes, and even lookouts specially selected for superior night vision. Extensive live fire testing against actual target ships ensured torpedo reliability.

The culmination of Japanese efforts was the development of the surface-launched Type 93 oxygen torpedo (and the similar, but smaller, Type 95 submarine-launched torpedo). The Type 93 was a 24-inch diameter torpedo with a 1,080-pound warhead, which could range up to 22 nautical miles at 35 knots or 12 nautical miles at 50 knots, but would typically be employed between 6–11 nautical miles from the target (U.S. torpedoes were typically employed within 5 nautical miles). Although U.S. torpedoes were technically more sophisticated with their highly secret Mark 6 exploder, the Japanese weapons were much more reliable, relying more on a brute-force approach. Nevertheless, the use of compressed oxygen as an oxidizer, which was the key to the Type 93’s range and size, required the Japanese to successfully overcome numerous significant technological hurdles, which they did through extensive testing and lessons learned from a number of accidental explosions. It took them from the early 1920s until 1935 to do it. Although both the Royal Navy and the U.S. Navy had experimented with oxygen torpedoes (and the British Nelson-class battleships carried them in the early 1920s), their development had been essentially abandoned due to the inherent danger of the use of compressed oxygen. Additional advantages of the Type 93 were that it could be fired from outside the range of U.S. searchlights, and the use of compressed oxygen resulted in very minimal bubble wake (caused by unburned nitrogen in other torpedoes). In many cases, U.S. ships were hit by Japanese torpedoes before they even knew the Japanese ships were there, sometimes believing that the torpedo had come from a submarine.

Because the Type 93 torpedo was potentially as great a danger to its own ship as to the enemy, the Japanese torpedomen were the elite sailors of the Japanese navy and were very highly trained and extremely secretive. The rest of the crew was generally completely unaware of what was really in the “secondary air tank” that stored oxygen for the torpedoes. As the Japanese lost air superiority during the course of the war, ships facing imminent air attack had to decide whether to jettison their Type 93 torpedoes as a precaution. At Midway, the Japanese heavy cruiser Mogami jettisoned her Type 93s and survived a severe pounding, whereas Mikuma did not, and the explosion of her own Type 93s inflicted fatal damage. At the battle of Santa Cruz in October 1942, the heavy cruiser Chikuma survived because she jettisoned her torpedoes, whereas at the battle off Samar in October 1944, a desperately lucky 5-inch shot from the fleeing escort carrier White Plains (CVE-66) hit the heavy cruiser Chokai in the torpedo bank and she had to be scuttled.

Despite the danger to themselves, the Japanese employed the Type 93 with devastating effect early in the war. Allied forces first encountered the weapon at the battle of the Java Sea in February 1942, when a spread of Type 93s from the unseen heavy cruisers Haguro and Nachi sank the Dutch light cruisers De Ruyter (taking the task force commander Rear Admiral Karel Doorman with her) and Java; only through luck were the Houston (CA-30) and HMAS Perth spared. However, they were to be sunk by the same weapons from the Japanese heavy cruisers Mogami and Mikuma at the battle of Sunda Strait the next night. Type 93 torpedoes were primarily responsible for the loss of HMS Exeter in the Java Sea; Quincy (CA-39,) Vincennes (CA-44), and Astoria (CA-34) at Savo Island; Northhampton (CA-26)  at Tassafaronga; Helena (CL-50) at Kula Gulf, and of 11 allied and U.S. destroyers. Despite the pre-war intelligence report, U.S. operating forces remained ignorant of the Type 93’s true capability at great cost until examples were recovered intact following the Guadalcanal campaign in 1943.

Published: Tue Feb 27 11:18:15 EST 2018