The Japanese Island Warfare Battalion

During 1944 Allied intelligence began to consider the existence of a modified Divisional organisation tailored for island warfare.  While the Standard Division was still to be encountered on the Asiatic mainland in areas such as Burma and China, it did not lend itself to the demands of island defence.  A new type of Division, relying on Infantry Regiments of smaller size but with increased firepower, began to appear in the Pacific theatre.

Reports refer to these new Island Warfare Divisions as having two Type "B" Regiments, designed for defensive operations, and a third Type "A" Regiment intended to be highly mobile and for use in the counterattack role.  There is some disagreement in the reports as to whether the Island Warfare formations were to become the new standard for Japanese Infantry Divisions, or whether they were experimental organisations likely to be encountered only occasionally.  The eventual conclusion seems to have been a compromise, that the Island Warfare Division, while subject to variation, was likely to be the norm in the South West Pacific, but that mainland Divisions would retain the Standard format.

Island Warfare Battalion Type "A"

Battalion Headquarters (3 Officers, 42 men)

Battalion Train (3 Officers, 49 men)

Pioneer Platoon (1 Officer, 65 men)

Mortar Company (4 Officers, 151 men)

Company Headquarters (1 Officer, 16 men)

Three Mortar Platoons, each (1 Officer, 45 men)

Gun Company (3 Officers, 118 men)

Company Headquarters (1 Officer, 18 men)

Mountain Gun Platoon (1 Officer, 73 men)

Anti-tank Platoon (1 Officer, 27 men)

Three Rifle Companies (6 Officers, 191 men), each comprised of;

Company Headquarters (1 Officer, 20 men)

Machine Gun Platoon (1 Officer, 34 men)

Mortar Platoon (1 Officer, 26 men)

Three Rifle Platoons, each

Platoon Headquarters (1 Officer, 1 man)

Grenade Discharger Squad (8 men)

Four Rifle Squads, each comprised of 7 men

Total Strength of 1030 all ranks (32 Officers and 998 men)

Points of note

The Type "A" Battalion was thought to be used for counterattacks in island defence and optimised for movement by a Divisional Sea Transport Unit.  There is no breakdown given for the subunit size of the Gun Company, so the figures in italics are my estimates.  This is despite there being four different suggested tables of organisation for the Battalion, all of which contradict one another on the strength of the subunits in the other Companies!  The figures above are taken from the most detailed of the three options, except the Rifle Company which is the one that made the most sense.  A fourth estimate shows the Battalion Headquarters and Train at the same strength found in the Type "B" Battalion, reduces the Pioneer Platoon to 50 all ranks and the Gun Company to 97, with two mountain infantry guns rather than three, for a total Battalion strength of 960 men.

The elements of the Battalion

Pioneer Platoon - the only mention of a Pioneer Platoon comes with this form of Battalion.  It is shown as having four Engineer Squads, plus a Material Squad, which presumably handled stores and supplies.  There is reference to the Platoon having both an unspecified number of flamethrowers and also three 81-mm mortars.

Mortar Platoon - in the Type "A" Battalion there was a sizeable concentration of mortars.  Each Platoon had four 81-mm weapons, of which there were two versions in use with the Japanese.  The Type 97 was almost identical to the US 81-mm M1 mortar, so much so that the ammunition was interchangeable, both weapons being derived from the Stokes-Brandt mortar.  The Type 97 had a range of approximately 3000 metres and weighed around 66 kg complete.

During the war another 81-mm mortar was introduced, the Type 99.  This was a much lighter weapon, weighing in at about 24 kg, due largely to a shortened barrel, and could be trigger fired.  It seems that the Type 97 had a similar range to the Type 99, despite the shorter barrel, which usually leads to a reduction in range.  There is no indication as to whether the Mortar Company of the Battalion used one or other version of 81-mm mortar, or both.

Mountain Gun Platoon - operated three 75-mm mountain guns, which again could be of two types.  The original Type 41 dated back to 1908 when it was used by the artillery arm before being issued to Infantry Regiments as it was superseded by newer equipments.  Its replacement was the Type 94 (1934), which weighed in at around 550 kg and could be broken down into eight major components that could be carried by horses or manhandled over rough and broken terrain.  Range differed depending on the type of ammunition and version of the gun but was approximately 8000 metres.  

Anti-tank Platoon - had two 37-mm calibre weapons, either the Type 94 or the later Type 97.  This was a pretty much straightforward copy of the influential German Pak 35/36 described elsewhere.  It was lightweight and mobile but its 37-mm round was ineffective against tanks such as the Sherman.  

The Rifle Company - this was a stronger Company in terms of both manpower and firepower than the Standard version.

The description of the Rifle Platoon varies from 38 to 42 all ranks.  Using the former figure this would allow for a HQ of an Officer and NCO with four Rifle Squads each of seven men and one Grenade Discharger Squad with eight men.  An alternative breakdown gives each Rifle Squad eight men, which is perhaps another indication that Company runners were detached from the Platoons.  In any version the Rifle Squad had a single light machine gun, and the Grenade Discharger Squad four launchers.  

There were all two support Platoons.  The Machine Gun Platoon (given as either 32 or 35 all ranks) had two heavy machine guns and one 20-mm automatic rifle.  The automatic rifle was the Type 97, an incredibly heavy weapon, fed from a seven round top mounted box.  It was capable only against very lightly armoured vehicles but could fire a high explosive shell as well.  The Mortar Platoon (given as either 27 or 29 all ranks) had two 81-mm mortars, which as mentioned above could be either the Type 97 or Type 99, though the lighter Type 99 would seem more appropriate.

Island Warfare Battalion Type "B"

Battalion Headquarters (3 Officers, 31 men)

Battalion Train (3 Officers, 30 men)

Infantry Gun Company (3 Officers, 80 men)

Company Headquarters (1 Officers, 20 men)

Infantry Gun Platoon (1 Officer, 33 men)

Anti-tank Platoon (1 Officer, 27 men)

Three Rifle Companies (5 Officers, 150 men), each comprised of;

Company Headquarters (1 Officer, 17 men)

Machine Gun Platoon (1 Officer, 22 men)

Three Rifle Platoons, each

Platoon Headquarters (1 Officer, 1 man)

Grenade Discharger Squad (8 men)

Four Rifle Squads, each comprised of 7 men

Total Strength of 615 all ranks (24 Officers and 591 men)

Points of note

As with the Type "A" there are three different suggested tables of organisation for the Battalion, with differing subunit strengths, the figures above being taken from the most detailed version, that for the Rifle Company again chosen as the most likely to my mind.  This was the Battalion type thought to be employed in the defensive role.

The elements of the Battalion

Infantry Gun Platoon - this served two 70-mm infantry guns as found in The Standard Japanese Infantry Battalion and was an important element of firepower as the Battalion had no integral mortars.

Anti-tank Platoon - as the Type "A" with two 37-mm guns.

The Rifle Company - used a similar Rifle Platoon to that of the Type "A".

Estimations of Platoon are given variously as 34, 38 or 42 all ranks across the reports.  34 would suggest just a six strong Rifle Squad, which seems particularly low by Japanese terms, while 38 could allow for an eight man Rifle Squad less one man acting as a Company runner. Platoon support weapons were again four light machine guns and four grenade dischargers.  The Machine Gun Platoon had just two Squads each with a single weapon and is shown variously as 19, 23 or 27 all ranks.  

Interestingly, there is a vague contemporary description of this Company from a captured Japanese document.  This gives the Company one Captain, four Lieutenants, two Warrant Officers, three Sergeants, 17 Corporals, 124 Privates and three Medics.  That actually gives a total of 154 all ranks, so someone seems to be omitted from the tally.  If otherwise accurate however, it may add weight to my suspicion that the three Platoon Sergeants doubled as the Company NCOs responsible for liaison, ordnance and supply duties.  The 17 Corporals at least matches with the number of Squads found across the Company.


By 1944 the euphoria that had accompanied the campaigns of the early war years, when their enemies fell before them without exception, had been extinguished.  The Japanese military was reduced to fighting a series of delaying actions across the expanse of the Pacific ocean, on rocky island outcrops that most people did not even know existed.  The average Japanese soldier was required to stay at his post until the enemy either overran him, or undertake one last futile banzai charge counterattack against the waiting machine guns.  Tales of Japanese soldiers stubbornly refusing to evacuate strongpoints or caves, despite being out of supplies and ammunition, are legion.  Even the appearance of a flamethrower could not dissuade them from their oath.  

Those Japanese soldiers who did surrender, or were captured so weak from starvation they were unable to resist, entered an odd twilight world.  Some hoped their captors would kill them, not nurse them to health and house them in tolerable conditions before repatriation.  It made for a tragic irony at the cessation of hostilities.  Allied prisoners of war, both soldiers and civilians, found the transition from the nether world of Japanese confinement back to reality sometimes impossible.  Japanese soldiers, presumed dead by their families, returned home shamed for having succumbed to capture.  The casualties of the war in the East continued to suffer long after the last shots rang out.

Return to...


The Japanese Army

The Japanese Infantry Battalion

Japanese Divisional Organisations

Site Map