naval units of the Imperial Japanese Army

[tom!]

Hi.

It is a less known fact that the japanese army had a large naval branch, too. It consisted of special landing craft motherships, transport and supply vessels, landing craft in various sizes, armed landing support ships, speedboats and even escort aircraft carriers and transport submarines. IJA employed up to 300000 soldiers for naval duties and managed up to 30 % of the japanese merchant ships during the war.

The first sino-japanese war 1894/95 showed that an island army like the japanese army depends heavily on shipping. This includes troops, material, supply and reinforcements. As the IJN was (at this time) small and mainly built for high sea duties it could provide only limited support.

In the mid-twenties the decision was made to build up am army naval branch. As IJN had no infantry elements at this time one of the main purposes of the army naval branch had to be amphibious landings and supply of the landed forces.

Due to the poor finances after the large earthquake in 1923 it took more than 10 years to develop and buy the needed landing craft and support ships.

In 1935 the world´s first special purpose landing craft mothership Shinshu Maru was commissioned. It couild carry several landing craft and landing support craft. During the innitial stage of the 2. sino-japanese war 1937/38 Shinshu Maru played a major role by supporting several amphibious landings along the eastern chinese shores.

Due to the raised funds IJA was able to lay down several more landing craft motherships in the late 1930th. Two of them were even designed to carry several aircraft which should be launched ashore to support the landing forces and to provide a minimal air cover.

During the innitial stage of the Pacific War they support several landings in Malaya, Philippines, Netherlands East India (today Indonesia), Borneo, various pacific islands and Burma.

As the tide of war changes in 1942 the japanese supply lines became more and more attacked by allied aircraft and submarines. The ship losses reached a dangerous level in 1943 and IJN wasn´t able to provide the necessary cover. So IJA decided to convert the landing craft motherships equipped with aircraft handling facilities to anti-sunbmarine escort carriers and to convert some merchant ships to escort aircraft carriers. Due to the lack of raw material the conversions took a lot of time and some were even not finished in August 1945.

In 1944 the foreward supply lines were almost cut-off by allied submarinnes and aircraft. So IJA started to built small fast transport craft and unarmed transport submarines to provide at least minimal support for foreward island garrisons.


In the following weeks I will add some short descriptions of the army crafts and vessels to this article.

Yours

tom!

[Antipodean Andy]

Well, there's something you don't read about every day!

[Adrian Roberts]

It is interesting that they were prepared to allocate equipment and roles to whichever branch of the service seemed appropriate. Their armed forces were new enough not to let tradition get in the way.

In many ways it is perfectly logical to have the army operate its lown landing craft, but in the Britain or the US, there would be a huge amount of vested interests and inter-service politics to get round first. Though to be fair, today's British Army does have a few of its own landing craft.

[tom!]

Hi.

Let´s start with the landing craft:

General:

The japanese army started development of landing craft in 1924. All types should also be used by IJN and as the navy had the necessary technical backgrounds development was done in cooperation with IJN.

The army needed two types of landing craft:

1. boats specialised on cargo/supply transport
2. boats specialised on equipment transport

In 1927 a cargo craft became ready for production. It was named "Army SB-C type" or "Shohatsu" (Sho-Hatsudo-Tei = small engined boat):



length: 10,6 m
width: 2,44 m
weight: 3,75 t
loading capacity: 3 t or 30 soldiers
engine: 1 X gasoline, later diesel with 60 hp
maximum speed: 10 kts
armament (IJN only): 1 X Type L 7,7 mm MG, later type 92 7,7 mm MG on the bow



It had a steel motorboat-type hull with a freeboard of 1,2 m and a spiral screw, which was useful to avoid the obstacles in the water. It was a reliable vessel and good in mobility. Shohatsu was widely used in China and in the early Pacific War. Some 1000 were built until 1943 and mainly used by IJA (IJN only bought 20).


In 1930 a larger landing craft became ready for production. It was named army LB-D type or "Daihatsu" (Dai-Hatsudo-Tei = large engined boat):



length: 14,88 m
width: 3,35 m
weight: 9,5 t
loading capacity: 12 t or 70 soldiers or 1 X type 89 medium tank or smaller
engine: 1 X gasoline, later diesel with 60 hp
maximum speed: 9 kts
armament (IJN only): 2 X Type L 7,7 mm MG, later type 92 7,7 mm MG or 2-3 type 96 25 mm aa-guns



Daihatsu has a steel hull and a spiral screw as well as Shohatsu. An armor plate was placed in the front of the pilot to provide cover against shots mainly from the front. A ramp was mounted at the bow to load and unload a vehicle or equipment. The bottom of the bow was W-shaped in order to stabilize the vessel when it lands on the beach. Some 6000 were built until 1945 with 3229 bought by IJN

Daihatsu was the most successful landing vessel of the IJA and it was widely used for the landing opertation and transport. Some were even armed with an AT gun or AA machine cannon and used as gun boat.

Yours

tom!

[Antipodean Andy]

Quite an interesting vessel. Simple idea but a couple of clever things like the spiral screw and W-shaped bow. Tom, do you know if any survived? I have this picture in my head of some Pacific island using one as their main mode of transport to the main island or something like that!

[tom!]

Hi.

Looking at the total production number I´m sure that a lot of Daihatsu landing craft survived the war but I haven´t heard of one on display in a museum.

Here is a nice japanese website with a lot of Daihatsu pictures loading and unloading vehicles and other equipment:

click me

By the way, here a picture of the standard japanese landing craft screw:




Infantry landing:



Yours

tom!

[tom!]

Hi.

With the introduction of the type 97 medium tank Chi-Ha in 1939 the Daihatsu landing craft was reworked to cope with the larger weight of the new tank (up to 16 t). In 1940 the new landing craft became ready for production. It was named "Army N-LB-D type " or "Toku Daihatsu" ("special Daihatsu").



length: 18,5 m
width: 3,70 m
weight: 17,5 t
loading capacity: 16,5 t or 120 soldiers or 1 X type 97 medium tank Chi-Ha or smaller
engine: 2 X diesel with 60-75 hp
maximum speed: 10 kts

The Toku-Daihatsu were larger and had two engines. Some 200 were built, the number bought by IJN is not clear


In 1942 the number of landing craft had to be enlarged within short time to cope with the needs of an ocean war. So a wooden model of the Daihatsu was developed and intoduced. It was named "Mokusei Daihatsu" (short: Moku Daihatsu; "wooden Daihatsu").



length: 14,55 m
width: 3,33 m
weight: 11 t
loading capacity: 10 t or 70 soldiers or 1 X type 89 medium tank or smaller
engine: 1 X diesel with 60 hp
maximum speed: 9 kts

Various sorts of wood and plywood were used for production and several minor changes were made by local yards. About 1140 were bought by IJN, several thousand more by IJA, correct number not clear.

Yours

tom!

[tom!]

Hi.

The Daihatsu landing craft were small and with limited payload.They had to be carried to the landing zones by landing craft motherships or transport vessels. They had to be loaded while laying besides the vessels making loading problematic even at quiet sea. And it took up to 17 hours to unload a vessel with 4000 t of supply using 2 cranes and several landing craft. This made supply during the early stages of an attack problematic.

So the decision was made to built several larger landing crafts with a higher transport capacity. IJN designed a special craft with a bow door, small draught and reinforced hull using an ice breaker design. The first ships of this new class were laid down in late 1941 and launched in 1942. The design was named "Army SS.1 type" / "Navy ES type".



length: 63,02 m
width: 9,60 m
displacement: 948 t
draught: 3 m
loading capacity: 630 t or 170 soldiers and 4 type 97 medium tanks Chi-Ha and 1 truck
engine: 2 X diesel, 550 -600 hp each
maximum speed: 13,5 kts
armament (IJA): 1 X Type 88 75 mm aa-gun, 1 X type 98 20 mm aa-gun, 4 X type 97 150 mm mortar, 4 X type 92 7,7 mm MG

The bow door had additional armour. Four type 97 150 mm mortars were mounted on the bow above the bow door for heavy close-range fire support. The machine guns were mobile. Mortars and machine guns could be transported ashore. Later during the war additionally several depth charges were loaded, too.

23 ships were built for IJA, few more for IJN. 4 more were laid down but destroyed or broken up before launch. 9 survived the war more or less damaged. Some were used for repatriation service and all were converted to small merchant vessels in 1946.

Yours

tom!

[spidge]

Interesting info Tom!

They needed them as they did a lot of landings!

[Antipodean Andy]

Good stuff, Tom. I always like seeing "obscure" (not widely talked about) gear surviving the war and being used - like the Army SS.1 type. I'd be surprised if any of those survived but I'm always surprised when I find out a Little Ship from Dunkirk or heavily modified MTB is found so there's always hope.

Re the Daihatsu - the sign of a good design - easily modified for other uses!