Tuesday, May 26, 2015


In the aftermath of Rizzo's attack on Wien, the Austrians strengthened their boom defenses until hand-held hydraulic shears could no longer overcome them. The Italians responded with a special type of MAS, the Grillo or "Cricket." This was a slow, quiet, electrically driven boat inspired by the British rhomboid tanks. It combined the flat-bottomed hull of a landing craft with a pair of 45-cm torpedoes in side-dropping gear and two hook-studded, engine-driven chains mounted on either side of the hull. The Grillo could approach boom defenses quietly and clamber over them, much like a tank crushing barbed wire. Once inside the anchorage, it would attack with its torpedoes and retire the way it came. The Grillo was not very successful in action. The chain mechanism produced a frightful clatter that all but negated the advantage of the silent, 15-hp electric motor. They were usually destroyed by shellfire before they got over the booms. Nevertheless, the Austrian navy was interested enough to raise and copy a sunken example.

Although the Italian Navy started to test its first motor torpedo boats as early as 1906, it was only after Italy's entry into World War I in May 1915 that development progressed. The first craft was commissioned in April 1915, and was soon in production by the Venetian firm SVAN (Societa Veneziana Automobili Navali), so was named Motobarca Armata SVAN, `SVAN armed motorboat'. Following mass production by Isotta Fraschini and FIAT as well, it was renamed Motoscafo Armato Silurante, `armed torpedo motorboat', or MAS. (This acronym was also used for Motoscafo Anti Sommergibile, `anti-submarine motorboat', in which role these craft were sometimes used.) The concept of a motor torpedo boat not only introduced a major change to Italian naval doctrine, but also led to development of other special craft. These included the tracked light assault boat, specifically designed to climb over protection nets; and the `mignatta' (`leech'), subsequently developed into the Torpedine Semovente Rossetti or `Rossetti self-propelled torpedo' - the first attempt to modify a standard torpedo for manned use.

During World War I the Italian Navy mostly fought against the Austro-Hungarian Navy in the narrow waters of the Adriatic Sea. Both sides tried to avoid any fleet engagement that might have cost them irreplaceable major warships, and this led to the development of craft and tactics for `small warfare', with the aim of causing as much damage as possible while putting at risk only light and easily replaceable craft. For Italy, this effort was quite successful. By 1918 some 419 MAS had been produced, 244 of them operational; their most significant successes were the sinking of the Austro-Hungarian battleship Wien on 9 December 1917, and of the dreadnought Szent Istvan on 10 June 1918. But the real step forward was the employment of assault craft, which brought a new dimension to naval warfare. On 13 May 1918 the tracked assault boat Grillo (`Cricket') tried to penetrate the Austro-Hungarian naval base of Pola on the Istrian peninsula (today's Pula, Croatia), and though it ultimately failed it did overcome four of the first five obstacles it encountered.

Italy had now been at war for several years and needed a way of successfully attacking the Austrian main naval base at Pola, another craft had been developed by the Italians called the Grillo which was a fast boat armed with a torpedo, attached to its sides were tracks with hooks so it could haul itself over the tops of booms and torpedo nets. Its first attack was against the ships inside the defended harbour at Pola on the 13th May 1918 but it was a complete disaster, with the craft being put out of action and the crew being taken prisoner.

Another notable mission - although carried out at the time of the Austro-Hungarian surrender, after the fleet had been handed over to the future Yugoslavia - was the sinking of the battleship Viribus Unitis in Pola harbour on 1 November 1918 by a manned torpedo. (This did not really navigate underwater, but was manoeuvred under the bow of the battleship by swimming frogmen.)

By October it was decided it was time for Rossetti and Paolucci to try the craft, so on the night of 31st October 1918 with the Mignatta being carried on the deck of a torpedo boat and escorted by another boat, they left Venice and headed for Pola. When they were off the coast the Mignatta was lowered into the water and towed by the other boat until they were in reach of Pola harbour, they were on their own, it was now 2 am on 1st November. They entered the harbour after climbing over three sets of torpedo nets and pulling the Mignatta over the tops behind them.

Now inside the harbour they made for the Austrian Flagship Viribus Unitis, still undetected they approached the starboard side of the flagship, as they did the Mignatta started to malfunction, the flooding valve on its stern had opened causing it to lose buoyancy and sink. To prevent this the compressed air used to propel the craft had to be used to correct its buoyancy this now meant it had insufficient compressed air to escape from the harbour after the attack.

Regardless of this they carried on with the attack, Rossetti released one of the charges and attached it to the side of the flagship and set the delay fuse for two hours and returned to the Mignatta. Paolucci now headed at full speed towards the shore hoping to try and escape overland, by now it was 5 am. They were spotted by the crew on watch and were illuminated by searchlights, as a motor launch approached them Rossetti quickly set the delay fuse on the last charge and pushed the Mignatta away into the darkness on a slow speed. Rossetti and Paolucci were pulled from the water and taken on board the flagship to be questioned.

At 6.20 am the charge exploded, the flagship immediately listed 20 degrees to starboard, the crew started to abandon ship taking the two prisoners with them, 15 minutes later the 21, 000 ton battleship rolled over and sank. The Mignatta meanwhile had circled the harbour until the air ran out and had settled on the bottom under the hull of the liner Wien, which was being used as a submarine depot ship, the charge exploded sinking the ship.

The two Italians were not prisoners for long as on the 5'h November the Italians occupied Pola, after the armistice both were awarded medals of honour for their bravery and for the building of such a successful new weapon .

Tuesday, May 19, 2015


Many submarines were modified to carry and launch three to six kaitens. The pilots entered the weapons while submerged through a connecting hatch. The ideal scenario would be for the mother sub to launch the weapons 7-8,000 meters from target. He would be on compass heading only and would risk use of the periscope only to acquire the target about 1-1,500 meters out.

The few successful contacts resulted in thunderous destruction but the vast majority of missions led to nothing at all. Kaitens must have missed entirely and ran out of power or were sunk by either enemy or mechanical failures. At any rate the successes did not justify the expenditure of lives.

Regarding the Kaiten carried by I-58 during the patrol, which resulted in the loss of the USS Indianapolis, the following details emerge. I-58 departed Kure on July 16, 1945 and immediately returned to repair Kaiten periscopes. On July 18, Hashimoto once again departed for his station east of the Philippines. 

At 1400 hours, on July 28, I-58 sighted what Hashimoto identified as a tanker and destroyer escort. He launched two Kaiten at this time and claimed two hits. In fact, the cargo ship Wild Hunter, and destroyer Lowry were the targets. Lowry sustained moderate damage from an explosion; the submarine was reported to authorities. Apparently, USS Indianapolis was not informed of this incident (she had departed Guam several hours prior to the attack) although Captain McVay was informed of IJN submarine activity in the area east of the Philippines. After the sinking of USS Indianapolis, Hashimoto proceeded to patrol for targets between Okinawa and Leyte. On the morning of August 10 Hashimoto launched a Kaiten against destroyer escort Johnnie Hutchins and a second against four of her sisters. He escaped upon the surface and claimed to have sunk two destroyers. 

In what would prove to be Hashimoto's last Kaiten launch during the war the USS Oak Hill -- a landing ship, dock -- and destroyer escort Thomas F. Nickel were sighted late in the afternoon of August 12, some 350 miles southeast of Okinawa. Identifying the vessels as a seaplane carrier and destroyer escort, Hashimoto launched his last operational Kaiten. At about 1830 hours Oak Hill sighted a periscope close aboard and maneuvered to evade. Nickel charged in to attack, heard the Kaiten scrape along her port side and watched the craft explode some 2,500 yards away. Hashimoto recorded the explosion and subsequent depth charging which the Nickel had commenced when Oak Hill reported a second periscope in the vicinity. Recording an apparent hit, Hashimoto returned to Japan immediately thereafter." 

My source is "Suicide Squads," by Richard O'Neill (published in 1981).


Used by the IJN in the final stages of WWII, the Kaiten Type 1 was a Type 93 torpedo modified as a one-man suicide weapon, although provisions were made for the pilot to escape before impact. In practice, however, none attempted to escape. With over 400 Kaitens built, only 100 were ever sent on missions, and out of those 100 missions only two succeeded in sinking enemy ships. In the end, the unmodified, unmanned Type 93 torpedo used conventionally was a much more effective weapon. 


Kaiten details

The Finemolds kit of the Kaiten is a Type 1 Kaiten and the Kaiten at Pearl Harbor is definitely one of the larger ones which is the Type 2 or 4, I cannot remember. The Kaiten Type 1 is 14.75 metres long and displaces 8.3 Tons and the Kaiten Type 2/4 is 16.5 metres long and displaces either 18.37 or 18.17 tons per Fukui's book. Also the Kaiten Type 1 had a crew of one as in the plans I have and the Type 2 or 4 had a crew of 2. From the 40 photos I have of the inside and outside Type 1 there is not a great deal inside to detail, so I think there is not much point in doing any interior modeling and sealing it up completely so you cannot see it yourself.

I think there is a bit of confusion here. The midget subs used to attack Pearl Harbour on Dec. 8 (Japan time) 1941 were NOT Kaiten. They were top secret midgit subs, the KOHYOTEKI. They were 2-manned midgit subs capable of carrying and firing two torpedoes. Although their chance of returning to the mother sub was slim, they were NOT suicide weapons.
KAITEN, on the other hand, was essentially a torpedo manned by a pilot(s) to ensure their success on hitting their target. They were used toward the end of the war, and they were indeed suicide weapons. Kaiten was NOT a submarine.

Fine Molds released both the KOHYOTEKI (midget sub) and KAITEN(manned torpedo) in 1/72. Perhaps this too contributed to the confusion here?

There is definitely a Kaiten Type 2 or Kaiten Type 4 at the museum at Pearl Harbor right now on display as of the last time I visited. I never said that a Kaiten of any type was used to attack Pearl Harbor in 1941. The Kaiten type 2 was the type that was being developed in 1944-1945 using the Type 6 engine which used hydrogen perioxide as an oxide for the fuel. When that failed, other efforts were made to convert it to other fuels, this was the Kaiten Type 4 which also was a failure. No Kaiten Type 2 or Type 4 ever reached operational use as they both were still in developement. I have a copy of the large U.S. Navy report from 1946 which covers all this history. The Kaiten now at Pearl Harbor is part of the very long list of submarine material that the "Naval Technical Mission to Japan" reported as brought back to the United States in about November of 1945. I have the complete list of all these items which includes "all" the Kaitens brought to the U.S., plus I have a 8" x 10" photo of the Kaiten at the Submarine Museum(Bowfin) at Pearl Harbor.


The Kaiten (Japanese: translated "Change the World" or "Reverse Destiny") was a torpedo modified as a suicide weapon, and used by the Imperial Japanese Navy in the final stages of the Second World War.

Early designs allowed for the pilot to escape after the final acceleration toward the target, although whether this could have been done successfully is doubtful. There is no record of any pilot attempting to escape or intending to do so, and this provision was dropped from later production kaitens, so that once inside, the pilot could not let himself out. In the event that an attack failed, the kaiten was fitted with a control for self destruction.

Five models were designed, the types 1, 2, 3 and 4 based on the type 93 torpedo (24 inch oxygen/kerosene), and the type 10, based on the type 92 torpedo (21 inch electric). Types 2, 4 and 10 were manufactured in small numbers and never used. Prototypes of the type 3 may have been built, or it may have existed only as a concept.

Only the type 1, a one person model with a 3000 lb (1,360 kg) warhead, was used operationally. Almost 400 of these were built, with more than 100 of these sent on suicide missions. As well as the obvious advantage of providing guidance for the torpedo, these kaitens could be launched from a submerged submarine, unlike the unmanned type 93 torpedo which was deck launched from the surface. However they were not nearly as effective round for round as the highly successful type 93 torpedo on which they were based. The American sources state that the only sinkings achieved by kaiten attacks were the tanker USS Mississinewa on November 20, 1944, and the USS Underhill on July 24, 1945 (some Japanese sources give much larger numbers).

The type 2 was intended to have a crew of two, and so is often confused with the Japanese midget submarines used to attack Pearl Harbor and Sydney. However the midget submarines used in these attacks were each armed with two light torpedoes in individual tubes, and were intended to return to their mother ships after firing them. All kaitens, on the other hand, had only fixed warheads, and were single mission munitions. The quality of construction reflected this fundamental difference.
All kaitens were designed to be launched from either the deck of a surface ship or the deck of a submerged submarine. Provision was made for the crew to enter the kaiten from the submarine while submerged. Having a very limited depth capability themselves, when carried on a submarine deck the kaitens similarly restricted the diving depth of the submarine itself. This is one of several factors blamed for the very poor survival rate of submarines using them, eight submarines being lost while sinking only two enemy ships and damaging some others. A submarine carried three to six kaitens.