Japanese Type 93 “Long Lance” Torpedo

Essential Question:

Why was the Type 93 Long Lance so dangerous?

Characteristics

• Length: 29.5 ft
• Diameter: 24 in
• Weight: 5,940 lbs
• Warhead: 1,078 lbs
• Propulsion: Kerosene-Oxygen Wet Heater
• Range & Speed:
  • 21,900 yd at 48-50 kts
  • 35,000 yd at 40-42 kts
  • 43,700 yd at 36-38 kts

Development

Aside from the big guns of battleships, the Imperial Japanese Navy strongly favored the use of torpedoes.  For torpedo attacks to be effective both at night and during the day, the Japanese needed a long-range weapon that would provide a tactical advantage.

Japanese experiments with oxygen torpedoes began in 1924 but were halted due to numerous failures.  In 1927, a naval delegation was sent to the Whitehead Torpedo Works to buy a regular Whitehead torpedo.  Impressed with the work, and under the mistaken belief that the Royal Navy was experimenting with oxygen torpedoes, they sent a report back to Tokyo the following year.  Shortly after that, Kure Naval Arsenal began work on creating an oxygen-fueled torpedo. By 1932, Capt. Kishimoto Kaneharu was leading the development. Other sources, such as Navweaps.com (2016) assert that the IJN began experimenting with oxygen-fueled torpedoes as early as 1917 and that the Japanese naval delegation to Whitehead had mistakenly believed that the British were developing a pure oxygen-fueled torpedo, when in fact, they were developing an oxygen-enriched torpedo.

Most torpedoes at the time used compressed air, fuel, and water to propel them.  If the compressed air is replaced with pure oxygen, then the saved weight can be used for increased range or warhead size.  Another benefit is that an oxygen torpedo produces a nearly invisible wake because the combustion products are highly soluble in water.  In contrast, a conventional torpedo produces a visible bubble wake from the expelled nitrogen in the exhaust. The British and American navies experimented with oxygen-powered torpedoes but dropped the projects due to technical difficulties.  One of the issues is that pure oxygen reacts violently with hydrocarbons such as oils and grease. These are particularly prevalent aboard ships, and indeed, inside the torpedo itself.

Captain Kishimoto and his team carefully designed a torpedo that would avoid the oxygen fuel coming into contact with lubricants.  The oxygen fuel lines, in particular, were carefully machined and cleaned to be free of oils and tiny pits where residual oxygen or lubricants could accumulate.  Natural air was used during engine ignition and oxygen was then fed into the system. By 1933, the IJN formally designated the torpedo as the Type 93 (1933 was the 2593rd year since the first Japanese Emperor according to the Imperial calendar). Initial trials took place aboard the cruiser Chokai.  The term “Long Lance” was coined by naval historian Samuel Eliot Morison and came into use after the war (Evans & Peattie, 1997, p. 266 – 267).

The Type 93 was officially adopted by the IJN in November of 1935 and used on class-A cruisers by 1938.  By 1940, improved models were being put on destroyers. Other versions included the Type 94 which was an aerial torpedo, the Type 95 which was a smaller submarine-launched variant, and the Type 97 which was used on midget submarines (Evans & Peattie, 1997, p. 270).  The Type 93’s speed and range far outclassed the U.S. Mk 15 that was in use on their destroyers and the Mk 14 that was used aboard submarines.

For comparison:

	JPN Type 93	USN Mk 15
Diameter	24 in	21 in
Length	29.5 ft	24 ft
Weight	5940 lbs	3841 lbs
Warhead	1078 lbs	825 lbs
Range & Speed	21,900 yd at 48-50 kts 35,000 yd at 40-42 kts 43,700 yd at 36-38 kts	5,000 yd at 45 kts 10,000 yd at 33 kts 15,000 yd at 26 kts

As impressive as its capabilities were, Captain Tameichi Hara (1967) notes that the torpedoes were so sensitive that they often detonated when they hit turbulent water, such as the wake of a ship (p. 179).  Furthermore, Joseph Czarnecki (2000) also writes that the Type 93 did suffer from duds and occasionally ran too deep causing it to pass beneath the target. All of these problems were notoriously suffered by the U.S. torpedoes in abundance.  However, Czarnecki also notes that these are common defects in torpedoes which, by their very nature, are complex and temperamental weapons.

Training in the use of the Type 93 was intensive and every effort was made to keep the details of it a secret.  In his memoir, Captain Hara (1967) had this to say about the nature of torpedo training:

Every week our squadron would go out on torpedo firing-maneuvers.  The torpedoes were fired without warheads, as an economy measure, but were set to run just below the target to simulate a direct hit.  After three years of intense training and practice, my score was such that I began to have doubts about my marksmanship. I seldom scored any direct hits. (p. 27)

Captain Hara eventually concluded that his score was no better than any other destroyer skipper and that the Navy’s existing torpedo manual was flawed.  He endeavored to rewrite it. After much trial and error and reworking of the math, Hara (1967) finalized his research:

The accepted doctrine was to cover a total spread of 20 degrees in firing eight torpedoes.  After careful analysis of all the many factors concerned, I concluded that the 20-degree spread resulted in hits only if my destroyer, describing a hyperbolic curve at 30 knots, released its torpedoes at the peak of the hyperbola, at a target 2,000 meters distant, starting to draw away on an evasive curving course at 20 knots. (p. 28)

While Hara does not go on to describe his finalized tactical solutions, he seems to be pointing to an established doctrine that only worked in a very specific circumstance. During training maneuvers, Hara (1967) recalls that orders were given to close to within 500 meters of a target before firing, but notes that this was rarely followed. He also remembers that the secrecy was so adhered to in training that the ships had to recover every torpedo fired and would often spend hours looking for a missing one. Even on days with rough weather, training would be canceled for fear of losing torpedoes (p. 30).

Lack of American Intelligence

Apart from the intense secrecy surrounding the Type 93, what is even more embarrassing is the failure of U.S. naval intelligence to effectively assess its capabilities. In a classic example of military intelligence being a contradiction of terms, the U.S. could very well have gleaned some of the performance characteristics of the Type 93 before the start of the Pacific War.  In 1940, Commander Henri Smith-Hutton, a U.S. naval attache in Tokyo made contact with a Chinese-Japanese man at a tennis club. The informant gained knowledge of the secret Japanese torpedoes after his school scheduled a visit to a Japanese destroyer.  Smith-Hutton taught him how to quickly estimate the diameter of torpedoes. The agent reported back to Smith-Hutton that the torpedoes were possibly as big as 25 inches in diameter rather than the previously thought 21 inches. Also, he told Smith-Hutton that a Japanese torpedo man proudly proclaimed that the torpedoes used only oxygen.  Smith-Hutton passed the information on to the Office of Naval Intelligence (ONI) on 22 April 1940. They gave no reply. It would not be until 20 April 1943 in ONI report 44-43 which concluded, based on prisoner interrogations, that Japanese cruisers and destroyers were indeed armed with 24-inch torpedoes (Prados, 1995, p. 31). By this time, the Japanese Navy had already wreaked havoc throughout the Pacific and it would not be until the summer of 1943 that the U.S. Navy finally ironed out the problems with its own torpedoes.

Tactics

One thing to know about the IJN was that they were obsessed with the concept of the decisive naval battle (kantai kessen 艦隊決戦).  Throughout the 1930s, the IJN made several revisions to its Battle Instructions. The Japanese were well aware of the U.S. Navy’s numerical advantage in light of the Washington and London Naval Treaties and sought to develop operational plans that would attrite the U.S. forces as they crossed the Pacific.  To effect a victory, the decisive battle eventually came to be comprised of two distinct parts. A night battle followed by a daylight engagement. The use of the Type 93 torpedo would have been integral to both of these. Given its impressive range, Japanese naval tacticians began to develop tactics for what was called long-distance concealed firing (enkyori ommitsu hassha 遠距離隠密発射).  This meant that cruisers, acting as advance units, would make contact with the American fleet before they had a chance to deploy into a battle line. The cruisers would then fire between 120-200 torpedoes from a distance of 20,000 meters.  They estimated that even if only 10% hit, there would be between 12-20 hits on the American ships, thus sowing confusion. (Evans and Peattie, 1997, p. 270 – 271). One of the Japanese plans for the decisive battle estimated that night torpedo attacks by cruisers and destroyers on the advancing U.S. fleet would see 25% of the torpedoes hit their targets.  A rather optimistic number (Prados, 1995, p. 61). The night battle prior to the daylight engagement would heavily feature the use of cruisers and destroyers to make torpedo attacks as they attempted to encircle the American fleet and catch them in a crossfire of torpedoes. All of this would have been done in close coordination with scouting aircraft and fast battleships acting in support (Evans & Peattie, 1997, p. 276 – 280).

Following the night battle, a daylight fleet engagement would have the Japanese aircraft carriers establish air superiority and then the fast battleships would create an opening for the cruisers and destroyers, under cover of a smoke screen, to make a torpedo attack on the American battle line with a total of 280 torpedoes.  By the time these torpedoes were expected to be hitting their targets, the main force of Japanese battleships would start to open fire and cripple the U.S. fleet. The cruisers and destroyers would continue to make torpedo attacks on American capital ships. Simultaneously, the fleet submarines and midget submarines would also be launching their torpedoes against the American ships.  

This was just a general overview of the Japanese battle plans from the mid-1930s and historians Evans and Peattie (1997) have noted that precise details from existing documents are vague (p. 282).  Very apparent is the importance of long-range torpedo attacks in whittling down the American forces. A detailed discussion of the Japanese plans for the decisive battle is not our focus here, however, several glaring flaws have been pointed out.  Firstly, if the Japanese tactics and strategies seem to be overly complex, it is because they are. The plans assume that the Japanese fleet would be able to coordinate themselves with clockwork precision. They also make very naive assumptions about how the American fleet would react. There seems to be a notion that the enemy would react in a very prescribed manner according to how the Japanese thought they would.  Secondly, several weapons, such as the midget submarines, that were to be used in the battle were still in development at the time these plans were drawn up. Indeed, the navy had not even tested these plans out in fleet exercises. Finally, there appears to be a strong mystical element at work in their thinking. Ever since the Japanese victory over the Russians at the Battle of Tsushima in 1905, the concept of a decisive battle had become an article of faith to them.  One can make a strong argument that Japanese planners ardently believed that the grace of heaven (ten’yu 天佑) would once again smile upon the Japanese fleet and magically grant them victory over their enemies (Evans & Peattie, 1997, p. 286).

Evaluation

It is easy to simply write the Type 93 off as being a superior weapon based on its performance characteristics alone.  However, an examination of its tactical usage in battle may reveal a different picture. T.J. McKearney’s (1985) analysis of the torpedo hit probability during the Solomon Islands campaign reveals an average of 6% for all engagements. Higher probabilities nearing 20% were achieved at the battles of Tassafaronga and Kula Gulf (as cited in Hughes & Girrier, 2018, p. 106). Joseph Czarnecki (2000) analyzed 21 naval battles where torpedoes played a role and assuming that the Japanese were aiming for a hit rate of about 15%, the actual results were below the mark.  Analysis of the results revealed an average hit rate of 6.71% or about 1 hit per 16.76 torpedoes fired. Extrapolating the actual hit rate to the IJN’s decisive battle scenario, if they fired 130 torpedoes during the night battle, then only about 9 would hit. Of the 280 torpedoes fired during the daylight battle, only about 18 would hit.  Czarnecki concludes that the Japanese did not achieve the hit rate or efficiency that would have allowed them to be successful in the planned decisive battle. Furthermore, he also opines that, given the extremely poor hit rate in long-range battles such as the Java Sea and the Komandorski Islands, the speed of the Type 93 was more important than its range.  As a caveat, he does note that there is insufficient data on the ranges and speed at which each torpedo was fired and only a handful of battles were documented in enough detail to come to precise numbers.

Overall, it is evident that the Type 93 torpedo was an extremely impressive weapon that outclassed all of its competitors in terms of performance.  However, the actual results of its wartime usage reveal a weapon that was technologically superb, but underutilized tactically and overemphasized strategically.

References

Czarnecki, J. (16 April 2000). Were the best good enough?: The Performance of Japanese Surface Forces in Torpedo Attack versus the expectations of the Decisive Battle Strategy. Retrieved from http://www.navweaps.com/index_tech/tech-067.php

DiGiulian, T. (12 May 2008). Torpedoes of Japan WWII. Retrieved from http://www.navweaps.com/Weapons/WTJAP_WWII.php

DiGiulian, T. (8 May 2016). Torpedoes of Japan. Retrieved from http://www.navweaps.com/Weapons/WTJAP_Main.php

Evans, D.C. & Peattie, M.R. (1997). Kaigun: Strategy, Tactics, and Technology in the Imperial Japanese Navy, 1887-1941. Annapolis, MD: Naval Institute Press.

Hara, T. (1967). Japanese Destroyer Captain: Pearl Harbor, Guadalcanal, Midway – The Great Naval Battles as Seen Through Japanese Eyes (F. Saito & R. Pineau, Trans.). Annapolis, MD: Naval Institute Press.

Hughes, W.P. & Girrier, R.P. (2018). Fleet Tactics and Naval Operations. (3rd ed.). Annapolis, MD: Naval Institute Press.

Prados, J. (1995). Combined Fleet Decoded: The Secret History of American Intelligence and the Japanese Navy in World War II. Annapolis, MD: Naval Institute Press.

Stille, M.E. (2013). The Imperial Japanese Navy in the Pacific War. Oxford, UK: Osprey Publishing.