Eu-II's 1/72 scale
Type A Midget Submarine

Kit Instructions

Translation by Allan McRae

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Below is a translation of the kit instructions from Eu-II's 1/72 scale Type A Midget Submarine. The Japanese text was translated by Alland McRae, and forwarded to HyperScale by Tony Rigby.

1/72 Imperial Japanese Navy Special Submersible

Kouhyouteki A-Type Used in the Pearl Harbour Attack

Kit No. EM 72-02

First Special Attack Unit Order of Battle

The Development of the Kouhyouteki 

The planning for a midget submersible, which later came to be called the Kouhyouteki, commenced in 1932. There are many theories about the origin of the concept, but according to Mr Shizuo Fukui,”The so-called special submersible commenced with research by the Imperial Fleet Main Torpedo Department, which got the idea from the suicide torpedo concept put forward by a Colonel in the reserves.” That is to say, the idea was to use battery torpedo technology to approach enemy ships underwater and at high speed to carry out a surprise attack using torpedos. So development commenced not so much on a submersible, but rather on a large torpedo which would carry a crew. It was one desperate measure used by the Japanese Navy, which at that time faced heavy restrictions on the possession of capital ships under the terms of a disarmament treaty. 

So, in this way, the development of a midget submersible to be treated not as a warship but as a weapon went forward at the Kure Arsenal Torpedo Experimental Department, with two experimental vessels being produced in 1934. The first test vessels were torpedo-shaped with no coning tower and had the amazing speed, for a submersible, of 24 knots. It was quickly decided to put them into use. Two improved vessels were produced in 1938 and the name was standardized as Kouhyouteki to take the place of previous names used for security reasons, such as A-Teki, Anti-submarine bombing-Teki and TB Membrane-Teki. Mass production commenced in 1940 and, along with this, modifications were made to the seaplane carrier Chiyoda to enable it to carry 12 Kouhyoutekis. It was originally intended that this vessel would be used to carry them.  

Next possible crew members and mechanics were assembled and training began under top security. There was movement in the Kouhyouteki towards the outbreak of hostilities between Japan and the US.

In decisive naval battles, the Kouhyouteki Units would be launched from the Chiyoda and other carriers before their main force comrades opened fire, then close in to and come to grips with the enemy.  

Then they would gradually reduce the fighting strength of the enemy by means of surprise torpedo attacks and afterwards swing the battle to their favour. This was the blueprint drawn up by the Imperial Japanese Navy for warship battles between Japan and the US.

Structure and Performance 

The first Kouhyouteki that entered mass production was called the Kou (A) Model. The first specifications were 23.9 meters in length and a displacement, when fully submerged, of 46 tonnes. A secondary battery powered the 600 horsepower main motor, giving it a maximum underwater speed of 19 knots. Because the A Model did not have a self-charging diesel generator, it could not move at all after the power had been used up. Its underwater cruising range at full power was 16 nautical miles and 80 nautical miles at a much reduced speed of 6 knots. It was planned that only the crew would enter the Kouhyouteki after the warships had concluded their attacks (I’m not sure what this means; maybe that prior to entering the sub everything else was already in place-Allan). The two-man crew, consisting of a Captain and his second-in-command, were housed under the coning tower. Its fitted weapon was two Type 98, 45 centimetre, oxygen-powered “muzzle-loaded” torpedos with a range of 3,200 meters. The noses of the torpedos protruded (from their housing-Allan) at first, but at the time of the Hawaii operations they were fitted with a sealed cap. 

The Kouhyouteki, which could be called the crystallization of Japanese submarine and torpedo technology, considered to be far in advance of the other major world powers, was, again quoting Mr Shizuo Fukui, “In a manner of speaking, the vessel itself was a precision instrument.”, although it is true that, as a weapon, there were many problems requiring a solution because its structure was less that what was hoped for. Underwater trim maintenance was difficult, so control wasn’t crisp at all. In addition, structural problems caused the vessel to rear upwards and surface as far back as the coning tower when the torpedos were fired. The latter defect could not be avoided. Also, the crew faced many safely problems due hydrogen gas being generated from the secondary battery. Nevertheless, those chosen as possible crew members were selected with priority placed on their superb skill and wonderful of fighting spirit, underwent gruelling training, made this new weapon their own and waited for the opening of hostilities between Japan and the US.

The Pearl Harbour Special Attack Unit 

The Kouhyouteki was thrown into operations at the very start of hostilities, commencing with the Pearl Harbour attack on 8 December 1941. Its mission in this attack, so different to its original function, was to secretly enter Pearl Harbour and deliver a surprise attack on the ships there. However, this was an idea put forward by the crew and their strong hopes resulted in great part to its implementation. Although Admiral Isoroku Yamamoto, the supreme commander, said,”If it we can’t put a crew in it, it won’t be implemented” because at first the likelihood was small that it could take a crew, it gained approval because efforts were made to redevelop the Kouhyouteki into (a vessel-Allan) which could secretly enter harbours and ports and full consideration was given to its accommodating a crew. 

In order to be operational, the underwater cruising range of the Kouhyouteki was lengthened from 4 to 16 hours by increasing the gas reservoir for steering power instead of reducing part of the battery, and by fitting attachments at the bow, conning tower and near the screws to break anti-submarine nets. For secrecy, the redeveloped Kouhyouteki was called a special storage tube, stored on the rear deck of five submarines refigured to hold storage tubes and covered with canvas. Then they set out for Hawaii. 

They were designated the First Special Attack Unit and were given the mission of secretly entering the harbour prior to the commencement of hostilities, lying in wait and then commencing their attack at the same time as the air units. About five hours prior to the attack of the air units, a Kouhyouteki under the command of (Lieutenant Junior Grade) Yokoyama was launched on the 7th at 12:42 am (local time) about 10 nautical miles from the mouth of Pearl Harbour and all the other vessels were launched afterwards at intervals of thirty minutes. Then, at 3:42 am, the minesweeper, Condor, cruising near the mouth of the harbour, spotted something like a periscope and contacted the destroyer Ward, which was patrolling in the area.

Although the periscope soon disappeared, the Ward continued searching and at 6:37 am spotted a periscope trying to secretly enter the harbour tailing behind the Antilles, a warship on special duty. It attacked it furiously with mines and sunk it. This was the first shots fired in the Pacific War and the special storage tubes were the first vessels lost. Reports are that the Ward sunk another unidentified vessel soon afterwards at 7:30 near the mouth of the harbour. Then, shortly after 8 am, the air units commenced their attack and the whole harbour descended into confusion. Much is unclear about the activities of the special storage tubes in Pearl Harbour, but US records indicate that at this point at least two special storage tubes succeeded in secretly entering the harbour and it is confirmed that torpedoes were fired. There is, however, no confirmation about what happened to them. Amongst all this, the Kouhyouteki under the command of Ensign Sakamaki, which was launched last and with a faulty gyrocompass, in the end didn’t make it to the mouth of the harbour and ran aground onto a reef. Sakamaki was forced to escape, was washed ashore on the beach of Oahu Island and became the war’s first prisoner. 

In the end, none of the vessels of the First Attack Unit returned home. With the exception of Ensign Sakamaki, all 9 crew members perished. It quickly became known to the unit that Ensign Sakamaki was a prisoner and that the special storage tubes had fallen into US hands. In order to honour their bravery and with the aim of concealing that the Ensign and the Kouhyouteki had been captured by US forces, it was trumpeted to the Japanese people that the nine crew members were to be made war heroes.  

They were given a naval funeral, promoted two ranks and even were made the subject of a military song. The navy deemed the Kouhyouteki’s attacks a great success and formed a Second Special Attach Unit.

Subsequent War Record 

The targets for the Second Special Attack Unit were the Allies’ base in the South Pacific--Sydney Harbour in Australia-- and the port of Diego Suarez, which was located on the east coast of Madagascar and was the British Navy’s base in the Indian Ocean.  

There was a simultaneous attack on these two bases on 31 May 1942. Three vessels attacked Sydney, sinking the accommodation ship (actually converted ferry-Allan), Kuttabul, but none of them returned home. On the other hand, the two vessels that secretly entered the port of Diego Suarez sunk the oil supply ship British Royalty and seriously damaged the military vessel, Ramirez. While this was a good military accomplishment, neither of these two vessels, too, were able to return home.

So, none of the Kouhyouteki which carried out these two harbour attacks returned home. But some say that this is because not only were there still many deficiencies with the vessels as a weapon, but also that it was too much to expect the Kouhyouteki, which was originally developed for hit and run use during warship warfare, to be used as a vessel having the endurance to secretly enter, at low speed, heavily guarded harbours and ports. Moreover, while some say that the crew of the Kouhyouteki carried out their attack resigned to not returning, it is a fact that the submarine (from which it was launched-Allan) continued to wait for its return at the rendezvous point and, disregarding its own safety, surfaced and then searched (for the Kouhyouteki-Allan) along the coast. It worked hard to retrieve the Kouhyouteki. Even so, much can be said and written about the bravery and technological skill of the crew, which undertook the difficult mission of secretly entering a harbour in a very imperfect weapon and with little hope of survival. 

Utilizing the Kouhyouteki for attack on harbour and ports being viewed with pessimism, it was then used for local defence and attacks on coastal anchorages where movement could be relatively freer. In July 1942, six vessels set out for the Island of Kiosk in the Aleutians to help with its defence and this was followed in November of the same year when they were thrown into offensive and defensive operations around Guadalcanal. In particular, the Third Special Attack Unit carried out eight attacks on a fleet of American transport ships at their anchorage in Lunge in Guadalcanal. Five crews of the eight participating vessels survived, sinking at least two transport ships and inflicting very heavy damage of two more. So, in this way, finally the Kouhyouteki was able to demonstrate its ability, was further developed into the C-type with increased range due to its ability to recharge (its own batteries-Allan) and was thrown into battle all over the Pacific, which was increasing in intensity.  

Painting and Markings

 Hawaii: Attack on Pearl Harbour

December 1941

Signal light: white

Decal No 8 on both sides

Hull overall: 33 flat black

Vessel No. 34: Kiska Island and Narumi (?-Allan) Island

August 1943

Signal light: white

Decals Nos. 8 and 9 on both sides

Vessel No. 36: Kure and Ourasaki Bases

August 1944

Decal No. 7 common to all three vessels

Signal light: white

Decals Nos. 8, 11, 12 and 13 on both sides

Small decal No. 1: on same place on Vessels No. 34 

Stand Placement

Position the stand on decals nos. 4 and 5

Colour 32 Warship color; dark glay (sic) 

On the painting of the Kouhyouteki 

Prior to the outbreak of hostilities, the Kouhyouteki was painted in a warship colour, but following the commencement of the war it seems that this was changed to an overall colour flat black. 

Although it appears that in general the vessels' serial numbers were painted on the side of the conning tower and the hull, this cannot be confirmed in the case of those that participated in the attack on Pearl Harbour. 

In addition, small parts of the vessel, including the torpedo heads, periscope, screws and so one were also painted black because of the nature of their function. 

This kit gives you decals to replicate the markings of three kinds of Kouhyouteki, the one that attacked Pearl Harbour and Models 34 and 36. Please decide which one you want to make because starting your model. In the case of Models 34 and 36, there are some parts that you don’t need to use and some that need to be modified simply. Please follow the instructions. 

Hull assembly 

Prepare hull parts 1 and 2, apply glue lightly here and there and cement together. Once they are in position, the application of liquid cement should produce a clean join.

The hinge faces forward (on the coning tower-Allan) 

If you are making Models 34 and 36, the protruding part No. 10 should be cut this way. 

Nose cap: the groove goes uppermost. 

The nose guard was fitted Pearl Harbour, but in the case of the Sydney and Madagascar attacks, which occurred afterwards, a differently-shaped guard was used to allow the vessel to ride over such obstacles. In the case of coastal protection at Kiosk and other islands nothing was fitted.

Periscope attachment 

Part 12 does not need to be used in the case of Models 34 and 36.

First, attach part No. 8, insert part No. 12 as in the diagram and then attach part No. 9 last.  

Special Submersible and Kaiten units called their periscopes “special glasses” because security required that their use be concealed. 

Nose Guard Attachment 

Do not attach these guards in the case of Models 34 and 36. 

First, attach all parts No. 16 completely to part No. 14, thread it onto part No. 13 and attach it to the nose. Lastly, attach part No. 17. 

Screw Attachment

 Do not use Part No. 20 in the case of Models 34 and 36. 

Attach the screw guard first. There are two grooves and 4 indentations on the screw guard. With the indentations facing forward (towards the coning tower-Allan) and with the grooves on top and bottom, attach this part to the rudder. 

Reference: The rudder and screw guard were supported by stays. Because the molding process makes it difficult to reproduce these stays, only the bases of the stays have been molded. A convincing model can be made by reproducing the stays with stretched sprue. The lengths of each stay can be found in the diagram below, but it probably would be best to make them a little longer and then trim them to the correct length.

Stay Diagram 

Do not use stays Nos. 3 and 4 in the case of Models 34 and 36.

Stay number one 21 mill by 2

Stay number two 20 mill by 2

Stay number three 14 mill by 2

Stay number four 13 mill by 1

Stay number one, left and right

Stay number two, left and right

Stay number three, left and right

Stay number four, one underneath

Attaching small parts 

Reference: A jumping cable was stretched from the nose of the Kouhyouteki to the coning tower and then to the tail to enable it to ride over anti-submarine nets. A convincing model can perhaps be made by using something like fishing line to replicate the cable. The location of the cable and the way it was attached can be found in this diagram and in the side views on Page 4. 

Reference: The jumping cable that was stretched from the bow in the direction of the coning tower was threaded through a roller on top and in the front of the coning tower and then was secured by a hook on the hull just in front of the coning tower. The hook can be replicated by twisting a thin length of wire as per the diagram. 

The stands, parts Nos. 24 and 25, should not be attached. The two stands are different, so refer to Page 4 for their correct location. 

Reference: The jumping cable on Models 34 and 36 was attached differently. The location of the cable and the way it was attached can be found in this diagram and in the side views on Page 4.

Translation by Allan McRae
Page Created 01 December, 2005
Last Updated 01 December, 2005

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