The Evolution of the Japanese Army Steel Helmet (1918-1945) Revised and Expanded Version
Article about: The Evolution of the Japanese Army Steel Helmet (1918-1945) Prolog During the Russo-Japanese War, the army received a letter dated 28th April 1905 from a private inventor, who had the idea t
Official description at the time of introduction
Purpose: To be worn during combat when required.
Structure and function
The Type 90 helmet consisting of the shell, leather liner and chin strap. The shell is formed from a single sheet of special steel plating and has the liner and strap installed inside. It is available in two sizes of large and small, where large corresponds to the visor cap sizes 1 to 5 (60cm to 56 cm), and small corresponding to 6 to 10 (55 and smaller).
Fit to the individual’s head is achieved by adjusting the volume of the liner padding. Weight is 1 kilogram for the large helmet and 0.95 kilogram for the small size.
Before wearing the helmet, the liner padding is to be adjusted to achieve best fit to the individual, after which it is to be secured by tying the chin straps.
Prototypes and patents
November 1928: Folding Helmet
During the prototyping process, inventions required to be patented by the Army, so no private person should later demand credit and royalties. One such novel idea that applied for a patent (application no. 11453, November 1928) in the course of the development of the type 90 helmet was a folding steel helmet invented by Army Artillery Captain, Tadashi Sato, a Tokyo resident. Of course, as an Army officer, Sato had already signed his consent to hand over the rights to his design to the Army in October and as with all Army patent applications, it was handled as a secret patent that did not get posted to the public.
As can be seen from the field evaluation criteria, the Army was concerned with portability of the helmet when it was not in wear. As the official designation of Close Combat equipment suggests, the helmet was a weapon item for close combat use only and not meant for general wear as part of the uniform, the visor cap still being the official headgear. Thus a folding helmet was seen as a practical solution to facilitate portability. An example of this prototype survived and exists today in a Japanese collection.
April 1933: New Steel alloy patent
In April 1933, the patent office granted patent number 100433 for a new low manganese steel alloy for helmets, using chrome, molybdenum and vanadium. This patent was applied for in December 1931 as application no. 14144 and was the invention of Army Artillery Lt. Colonel, Masakuni Sugimoto of Nishinomiya City. Though this application was made only a year after the introduction of the Type 90 helmet, there is little doubt that this was what the Type 90 announcement referred to as the special steel alloy. This same officer had also been granted a patent in 1928 for a steel alloy for bullet shields and the 1933 patent appears to be a reduced manganese variant of this earlier work.
A secret order placed by Chiang Kai-shek in Nanking in the Spring of 1930 for Japanese Weapon supply included a request for 4 helmet samples of the new helmet, but the Army order releasing these samples specifically states that they were to be supplied in regular steel.
This patent was later declassified on March 31, 1936 by the Army, who no longer saw the need for secrecy.
Production ramp up of the Type 90 helmet by Kobe Steel and Japan Steel Works during 1931
The Osaka Arsenal contracted Kobe Steel (神戸製鋼所) to produce Type 90 helmets as well as personal body armor, but the manufacturer soon realized they needed to do their own testing on the firing range to optimize the helmet design for large scale production, and for this built their own range, but now they had to get hold of the special rifles and ammunition that the Army developed for helmet testing. First, in a letter dated August 27th, 1931 Kobe Steel requested the Army for the supply of the Army modified rifles. One, a Murata Rifle modified to 12.6mm caliber for helmet testing, and the other a Type 38 modified to 7.7mm for the armor program. This was immediately followed the next month with a request for 100 shots of ammunition for the guns. In order to be more efficient, Kobe Steel further decided to add testing of the steel sheets before production, and thus went back to the Army with another request for 200 rounds in October. The army’s criteria for this firing test was that a 12.6 mm lead ball shot of 10.6 grams was to be fired from a smooth bore gun at a residual velocity of 300 meters as measured 5 meters away from the gun muzzle and the dent in the helmet must be smaller than 20mm.
Then at the end of November 1931, a similar request was filed this time from the Nihon Seikou (Japan Steel Works日本製鋼) of Tokyo, who at the time was in the process of pre-production prototyping. They requested the 12.6mm Murata Rifle and 100 rounds of test ammunition.
1931-1932: Helmets to the front!
On September 18, 1931, just when production of the type 90 helmets had started to pick up, the Japanese Army staged a sabotage of the railway near Mukden to create an excuse to invade Manchuria.
This was the Manchurian Incident that will lead to the establishment of Manchukuo the following year. The Kwantung Army dispatched its troops, who arrived wearing their cherry blossom helmets received in the summer of 1928, and an order was placed for 24,780 Type 90 helmets to cover the immediate needs of the action in Manchuria. However, when in close succession, the Shanghai Incident of January 1932 broke out and stoked the fire in the Continent, the Army and Navy were all mobilizing, causing a rush for helmets.
A telegram classified “secret” dispatched on December 18th, 1931 from the Chief of Staff of the Kwantung Army addressed to the Vice Minister of the Army, reminded that the new troops to be sent to the continent should already come equipped with the new steel helmet and belt extensions (to make waist belt longer for wear over bulky winter wear) for the extreme cold climate outer wear. In order to cope with such contingency needs of newly formed units to be sent to Manchuria, the Army main arsenal was ordered to supply 1,000 helmets to the Kokura Arsenal and 3,060 pieces to the Hiroshima arsenal that month. And at the end of December, a request for 2,000 helmets from the Kwantung Army for its new troops was to be supplied to the 20th Infantry Division, which was to carry them upon their departure to the continent.
While the Navy swallowed its pride to beg the Army to sell them Army weapons and 1,700 old cherry blossom helmets to supply their Landing Forces bound for the continent, in February 1932, the Army dispatched a panicked telegram to its divisions remaining in Japan and its schools that they should return their type 90 helmets ASAP for forwarding to Manchuria.
1932: Helmet donations welcome
Whoever it was that got the idea, from this time, the Army would solicit helmet donations from the public, and thousands of helmets were donated to the cause of Manchuria already in January and February of 1932. These helmets came from the Veteran’s Leagues, The Patriot Women’s Leagues, etc, who would collect donations in cash and deliver that to the Ministry of the Army, who would have the arsenal turn them into helmets. At this time, a donation of 13.5 Yen bought the Army one helmet. This practice will continue for years, and donors would get a citation of gratitude, later ones in Tojo’s name as Minister of the Amy.
Summer 1932: Phasing out of the cherry blossom model
Finally, by summer of 1932, the supply of the new type 90 helmets for the Manchurian Incident had stabilized, and Army Manchuria Regular Ordinance 1769(陸満普第１７６９), dated July 22nd 1932 announced that all old type helmets in the Manchurian “Incident Theater of operations (Manchuria, China and Korea)” were to be exchanged with the new Type 90 helmet stocks from the Army Depot and costs charged to the Manchurian Incident budget. With this order, the old helmets ended their front-line duty in the Army, but continued to serve their new, but second hand owner, the Navy.
1932-1933: From a weapon to a uniform item
By Army Regular Ordinance 2748 (陸普第２７４８) of April 28th 1932, seven items formerly categorized as “weapons” were reclassified as “clothing items”. Among the human and horse gasmasks, anti-gas wear and body armor thus reclassified was the steel helmet. Some of these gear also went through a nomenclature change through this order and the steel helmet, which was hitherto called Tetsu Kabuto (鉄兜) was officially renamed Tetsu Bo (Steel Hat鉄帽), more in keeping with its new identity as a component of the uniform. The classification change also meant that the Clothing Main Depot (被服本廠) would now take over the helmet business from the Army Technical Headquarters, and the 1933, April memo from the Vice Minister of the Army to the Clothing Main Depot allocated a production quota of 50,000 helmets to be supplied by the end of that year, still a relatively small number.
Having production of cloth items and steel helmets under the same Army office must have made it easier for the Army to deal with the complaint from soldiers that their helmets baking in the sun were giving them serious discomfort in the field, as the clothing office promptly shipped out 3100 pieces of anti-heat helmet cover prototypes for the troops in China to test and finalize. These covers are discussed separately after this Type 90 story.
Army Regular Ordinance 4525 of July 26th 1932 followed through on the helmet’s change to a clothing item by instructing all that henceforth gas mask and helmet orders were to be placed with the Clothing Main Depot. This announcement also clarified the rule regarding repair of damaged helmets, which became the responsibility of the unit. Later shipping manifestos show that field units received all the necessary pieces ( liner, padding pouch for liner, rings for the straps, star insignia and paint ) to be totally self-sufficient in repairs
1935-1936: Boosting production
During November to December of 1935, Nihon Tokushu Ko (Japan Special Steel日本特殊鋼) of Tokyo obtained its tools of the trade, two modified 12.6mm Murata rifles and 1,000 rounds of the special helmet-testing rounds to join as a helmet manufacturer.
Another manufacturer, Daido Steel Company (大同製鋼) of Nagoya, also got tapped on the shoulder by the Osaka Arsenal around the same time and placed their request for the antique weapon the next month, in January of 1936.
In this manner, what started out as an annual production volume of 71,750 helmets in 1931 reached 430,000 units of accumulated production by 1936, and then in 1937 alone 420,000 were made, almost matching 6 years of production in a single year. This further almost tripled in 1941 to 1,135,900 units, 1942 at 1,546,000 units until starting to decline in 1943 to 444,000 units, 1944 to 366,200 units and 1945 ending with 10,700 units
Here are the typically found company markings for helmets. The Tokyo Arsenal stamp on top you will find in the 1922 Model and almost surely in the 1918 Model. The other markings can be seen on Type 90 helmets. Small and Large size markings were done in white paint under the rear chin strap ring for the army helmets. They are often stamped as well. Though collectors regard the small size as much rarer than the large, about 45% of actual issue was in small sizes. I checked records for more than 10,000 issued examples and small was consistently in the 40-45% range, so during the war small was only rarer by a hair.
1931-1937: Type 90 Helmet Supply to the Navy
During 1931 and 1932, many ships operating off Chinese shores put in requisitions for steel helmets for its Landing Force troops and gun crews, but none of these requisition forms specify helmet type until a requisition form dated June 8, 1933 from the Naval Propaganda Office requested 50 pieces of “Model 2” helmets along with an armored car from the Shanghai Incident for PR. As mentioned earlier, the Navy had bought 1,700 Cherry Blossom helmets from the Army in February 1932 for the Shanghai Incident, so now model names were given to tell them apart, giving rise to “Model 1”and “Model 2” designations.
The first requisition document that confirms availability of the”Model 3” or Type 90 is dated November 9, 1933 in which 280 Model 3s were supplied to the 26th Destroyer Fleet and all the requisitions from the beginning of 1934 consistently mention Model 3s by name, indicating that the type 90 helmet did not see too much circulation within the Navy until 1934. Circulation is the right word, because these were “loan” items in the Navy, and once the ship was taken off patrol duty of the Chinese coast, the helmets were returned to the depot for loan to other ships and their Landing Forces. As mentioned before, they were special weapons loaned out when close encounter with the enemy was anticipated. That changed for the Army when they shifted helmets to the clothing category, while the Navy persisted to treat them as weapons, suffering shortages when general mobilizations created a rush for the limited weapons supply.
Once Again the Navy is saved by the Army
Isoroku Yamamoto was still deskbound as the Vice Minister of the Navy when full-scale war with China (The China Incident) broke out in July 1937, causing an “all alert” situation. The following letter from him to his counterpart at the Army illustrates the Navy’s situation regarding helmets.
The advancing of steel helmet inventory August 25, 1937
Due to this incident we find ourselves in urgent need of the weapons below and would be grateful if you would arrange for us to draw from the inventory of your Ministry.
I would like to initiate discussions between those in charge at the working level on this matter. We will replace your stock by placing an order with the Army Clothing Main Depot.
Tetsu-Kabuto (Official Army Standard Model) 4,000 Pieces
Vice Minister of the Navy
Note Yamamoto’s reference to the helmets as a “weapon”. Also, the word for steel helmet he uses is the pre-1932 word Tetsu-Kabuto.
Helmet lining was most commonly in leather, having a thickness of 1.5 to 2mm for the main part, and thinner 0.8mm leather for the rear bag for the padding. The spec sheet from August 1939 allows for 6 different types of leather quality for the main body, which included pigskin and joined scrap leather. Towards the end of the war pigskin seemed to be the predominant choice for army helmet liners. Pigskin was particularly favored in the tropics for shoes, as the pores allowed for better ventilation to reduce clamminess. A similar benefit must have been there also in the case of helmet lining material.
An all canvass version was also available from mid December 1939 as is shown in the following spec diagram.
Tutorial : How to Tighten the Straps of your Kabuto
Let’s end the Type 90 story by showing you below the various chin strap tie methods used on helmets by the navy.
1. This is the way to tie the straps on the Model 2 cherry blossom helmets bought from the Army. But this is the early style method. Later the straps were lengthened to allow carrying by hanging on backpacks, which lead to the method shown as 5.
2. This is how the navy wore the Model 3 Army T 90s around 1937-38. The point was tying it in the back to prevent the helmet from dipping forward when you had to suddenly duck and crawl. Two variations of how it went around the chin are shown.
3. Typical prewar method for the Model 3 navy helmet. When wearing a gasmask they employed the so-called necktie knot that allowed easy adjustment of tightness and could easily be undone by a single pull.
4. Used on the Model 3s during WW2 when they made the straps short to conserve material. These were knotted at both ears and could be put on quickly just by tying the ends together.
5. The method used for the paratrooper helmet developed in 1941, as well as for the late style cherry blossomed helmets.
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