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The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)

Article about: The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945) Once again, please no interruptions until the last photo says THE END. Foreword In my past research on helmet covers, I cam

  1. #1

    Default The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)

    The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)

    Once again, please no interruptions until the last photo says THE END.


    In my past research on helmet covers, I came across quite a few documents discussing sun helmets, as they were often tested together in the same tropical test sessions in Taiwan. So when a recent question popped up about an early model sun helmet, I had a chance to review my files and thought I could have the whole picture of sun helmet development with only a little more digging for missing links. I was actually finishing a new complete history of the IJA’s pay book, but due to the lack of one early sample to study and confirm a couple of details, I had to shelve the project for later completion and was in search of a handy project instead.

    My brother is a leading collector of the Deutsches Afrikakorps of WW2, who is also a contributor to Dal McGuirk’s reference book classic, “Rommel’s Army in Africa”, so I have been quite familiar with German tropical items myself, but shamefully knew next to nothing about the Japanese effort in comparison. So it was also another chance for atonement for neglecting home ground. In the end, I have to say I am quite impressed with what I have now newly learned.

    Once again, I choose to follow the footsteps of the army designers from the very beginning till the bitter end. This is because product development is a continuous cycle and is never tied to specific wars, the way authors often like to chop things up into catalogs like “Uniforms of WW1” and “Uniforms of WW2”. Wars are just passing points along an endless highway of human drama, striving to improve upon the past.

    For me, writing a “Uniforms of WW2” book is as boring as just seeing a snapshot of men on the top of Mt. Everest. The devil is in how they got there, and that is the story I want to tell.

    Having to do it the hard way, is partly an occupational hazard in this case. I have had a long career as an automotive product planner, so I had the same type of work cycle like the army men who had to engage in this type of development work. The documents that they prepared and the analysis and meticulous attention to detail evident in their work are all marks of how I was taught to do things in my own job. What today’s businessmen call the “Plan-Do-Check-Action” cycle was practiced perfectly already in this sun helmet development work of 100 years ago, and I cannot help feel a certain bond with the men, as their reports expressed their elation in success and bitterness in failure, all seamlessly overlapping with my personal moments.

    One major bonus here of this “Evolutionary approach” was in learning about the huge efforts they made to use a diverse range of materials by borrowing from a wide range of traditional weaving crafts within Japan and Taiwan. So I went the extra mile to show you the widely different plants they worked with.

    This diversification of materials used, combined with simplification of specs were phenomenon seen across the board in IJA militaria and were all born, because of a material-starved economy in Japan. This so called “last ditch” symptom which many erroneously attribute to 1944/45 actually occurred between 1937 and WW2 in Japan, so it was a pre-WW2 development.

    I came to call them “B-spec” items here, and wish I had used that handy word earlier, as rubberized canvas, felt field caps and the so-called Type 3 sword; all these were “B-spec” fallbacks Japan devised at that time.

    This time, I am indebted to Jareth Holub for providing me with photos of his collection to help me illustrate the story and make it come alive.

    1887-1911 Colonial Predecessors of the Army Sun Helmet

    Initially a trademark of the British and French colonial look, the wearing of pith helmets spread worldwide from the late 19th to the early 20th centuries. However, despite of this worldwide fad, Japan was slow in coming to see any need for such gear. That was because being a late comer to the game of Imperialism, Japan did not hold any tropical colonies.

    But even so, the well-travelled Japanese Navy must have felt obliged to match the colonial style dress code when making port calls at tropical colonies of the European empires. Thus the Imperial Japanese Navy introduced a sun helmet already in 1887, nearly 40 years ahead of the army.

    Introducing sun helmets for wear within its own territory as a colonial necessity was a thought that occurred to Japan only after gaining Taiwan as territory, as a result of winning the first Sino-Japanese War of 1894/95. Taiwan has the Tropic of Cancer bisecting the island roughly at midpoint, making Northern Taiwan part of the Subtropics, and Southern Taiwan the Tropics. Head Quarters for the Japanese government outpost for Taiwan was set up in Taipei within the subtropics zone at the north end of the island, but when they made a request to establish uniforms for the Japanese workers and police there, their request included sun helmets as a matter of course.

    However, documents dated 16th March 1911, establishing these uniforms for the Taiwan bureaucracy were also accompanied by documents of protest from the Navy, which was strongly opposed to the uniform designs. They were throwing a tantrum claiming that a civil servant in the employ of the Japanese Governor-General of Taiwan, wearing his sun helmet, white uniform and dagger would look identical to a navy man.

    You could almost hear the sighs from the Prime Minister and others, as they patiently explained to the Minister of the Navy that the civil servant uniforms for Taiwan were not set up with shoulder boards, but sleeve insignia instead, so they could not be mistaken for navy. The Navy’s protest was overridden, but the fact that even documents signed by the Emperor in sanctioning the new uniforms saw it necessary to address the Navy’s argument point for point shows how jealously the navy tried to protect its own trademarks. They particularly resented the idea of non-military personnel wearing daggers, though they said they would let the sun helmet go, if the shape were suitably changed, not to resemble a navy one.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)   The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  

  2. #2


    1915-16 “Round 1” of Army Field Tests in Taiwan, the German War Booty Sun Helmets

    It was WW1 that suddenly changed Japan’s fortunes in the tropics. The former German islands in the Pacific such as Palau, Micronesia, Marshall Islands, surrendered to Japan, and Japan would now govern the area as the South Pacific Mandate. As the South Pacific suddenly became a vested interest for Japan, it followed that Japan also needed to defend these possessions.

    Thus in 1914, the army decided it was finally time to have tropical uniforms.
    As a happy coincidence, it was not only Pacific islands that Japan won, but also large stocks of pith helmets came with this victory over Germany.

    As the army was starting to consider a similar design, it decided to make use of this windfall to gauge field acceptance for such new headgear by issuing large numbers of these helmets to its troops in Taiwan.

    Back in 1907, the army had established two Taiwanese Infantry Regiments. The first regiment covered the mid to northern part of Taiwan, and the second regiment covered the south, so issuing them the German helmets allowed field tests in both subtropical and tropical climates at the same time. Thus in early August of 1915, 2,980 German Sun Helmets were shipped to Taiwan from the Hiroshima Depot.

    The troops in Taiwan were instructed to add Army visor cap stars and chin straps to the German helmets (The army referred to these as ヘルメット形夏帽 ”helmet type summer hats”). They were to wear them for two summers of 1915/16 and report on 7 points.

    (1) Handiness, (2) Effectiveness in preventing sun stroke, (3) Suitability as a summer hat, (4) Ease of Repair, (5) Resistance to rain, (6) Storage implications, (7) Improvement ideas based on field trial.

    The two Infantry Regiments were allocated 1,085 pieces each and the rest went to two Artillery Battalions (260 each) and two Mountain Gun Companies (145 each).

    The final verdict from Taiwan, dated 17th January 1917, found the helmet cumbersome to deal with in passing through thick growth and in combat action in comparison to a visor cap, but appreciated its protection against direct sunlight coupled with good internal air ventilation to prevent heat strokes.

    They also felt the helmet had good water repellency, but it did get uncomfortably heavy after prolonged exposure to rain. Repair seemed to be somewhat trickier than a visor cap, but within reason.

    All in all, they felt that it was a headgear worth having for summer, if some improvements could be made.

    They had 6 improvement suggestions. (1) Weight reduction (2) Lower dome profile (3) Flatter angle for the front visor and increased visor size (4) Smaller rear visor or a collapsible rear visor like the neck guard on Samurai helmets, not to interfere with wearing of backpacks and hoods (5) softer leather sweat band to prevent headaches (6) improved water repellency.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)   The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  

    Last edited by Nick Komiya; 10-18-2016 at 09:13 PM.

  3. #3


    1916-1917 “Round 2” First IJA Prototype Test in Central China

    Overlapping the last year of German helmet tests in Taiwan, in the spring of 1916, the Army also decided to run a field test of its own prototype design in subtropical Central China.

    Japan’s continued winning streak against the large empires of China, Russia and Germany in close succession became an inspiration to many independence movements in Asia, and China’s Qing Dynasty was toppled in 1912 by such a domino effect of the times, the Xinhai Revolution. As many must remember from the film, “The Last Emperor”, the Japanese were quick to see opportunities in this quickly developing vacuum in China and must have anticipated that the next theater for the army would be the Chinese mainland. It must have been this anticipation of impending military action there that made the army shift “Round 2” of the sun helmet tests to China from Taiwan.

    Between January 1912 and July 1927, Japan had an expeditionary force of 7,000 men stationed around Hankou 漢口 (present day Wuhan) under the pretense of protecting its own citizens there. It was these troops that got the homework of testing of the army’s sun helmet and tropical shirt prototypes during the summers of 1916 and 1917. They received delivery of 700 sun helmets.

    The Army still did not call them 防暑帽 (Anti-heat hats) as they would in WW2, but now called themヘルメット帽 (helmet hats). In English, there is also the commonly used word “hard hat” for modern work helmets, so the Japanese term is not actually as off as it might sound at first.

    By this time, they already had some feedback from the first summer of testing the German helmets in Taiwan, so though no documents clearly describe what this prototype looked like, it seemed to address already some of the criticism mentioned above in the Taiwan report.

    Of particular interest is that the rear visor was designed so it could be flipped up, not to get into conflict with the shouldered rifle or the back pack with coat strapped on top or when firing in a prone position. It seemed to have a black lacquered front visor, too. Two alternative chin straps were provided, one being a stiff type like the visor cap strap and another soft type. The body of the helmet was made from woven palm fibers (棕櫚). The top vent seemed to have a flower-shaped lid.

    These helmets were delivered to the troops by end of April 1916 and they were to wear them for two summers and report each year on 9 main points.

    They were; (1) degree of heat protection provided, (2) any restrictions to firing rifles in various stances, (3) implications of exposure to rain, (4) wear comfort, (5) ease of damage repair, (6) ease of storage, (7) suitability of chin strap choice (8) conspicuousness to enemy eyes, (9) any improvement suggestions gained from testing and comparison with standard visor cap.

    Strictly for testing in heat, Taiwan would have made more sense, because though Wuhan was normally known for its murderously hot summers, it was in the subtropics zone, not quite the tropics and this particular summer was much milder than usual. The report from China dated 13th November 1916 said humidity, that commonly rose above 90% to make it insufferable during summers, only hit that mark for 8 days in the 3 months of June to August that year.

    Also, though temperatures of more than 30 degrees centigrade should have been common, the average summer heat that year was only 27.8 degrees.

    Comments from the troops started out somewhat positive by lauding the good protection it provided against the heat, but they were only imparting the good news before the really bad, as it became quite a scathing criticism towards the end, when the final verdict came from China after the second summer dated 15th November 1917.

    The executive summary said “Though it is not unsuitable for military use, many improvements are still needed.” The heat alleviating properties were consistently well received, but even with the flip-up rear visor, problems persisted in shooting in the prone position and with snagging on the pack when moving the head.

    They even suggested the flip-up structure should be a spring-loaded one to keep the visor properly held up, all the way up to a 90–degree angle. They also said the front visor should be made to flip up, and instead of glossy black lacquer, plain cloth or at least a matte finish was suggested.

    Water repellency was generally good, but when it did eventually get soaked through, the woven palm fibers created a warped and lumpy surface when dried up, so they suggested using light cork or gourd sponge instead as shell material.

    The glued-in flax lining under the sweatband was quite stiff, so combined with the weight of the helmet (in comparison to the visor cap) some started to get headaches only 1 hour after putting the helmet on.

    Thus height and weight reduction of the overall design was requested as an absolute must. Repair work by the soldier in the field was rated as a totally hopeless proposition. The flower shaped vent lid on top often got ripped off, because of poor soldering to the fixing screw.

    The lacquered leather sweatband soon lost all its finish after absorbing sweat and did not last even one summer, so the material used in visor caps was suggested. In terms of concealment from the enemy, the troops did seem to be quite content.

    All this still sounded like constructive criticism, while they patiently addressed the obligatory check items one by one, but they had saved the worst for last.

    The report ended by saying “ In a region of extreme summer heat like Wuhan, not only Europeans, but also the Indians, Chinese and others who need to work outdoors have devised various types of “helmet hats” out of long experience. In comparison to those native models, the prototypes in question are far inferior in both quality and design. The design is outright ugly and the exaggeratedly high dome of the sun helmet on a tiny Japanese soldier looks totally out of balance and ridiculous. The helmets worn by the Chinese constables and mailmen in the international concession areas are far more dignified in comparison. Even in short maneuvers, durability has proven to be far from satisfactory, so continuous exposure to the elements would surely cause them to fall apart and lead to a flood of replacement demands from the field. A serious attempt should be made to collect and study headgear already out there.”
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  

  4. #4


    1921 “Round 3” Second Prototype Testing in Taiwan

    While the expeditionary force in China was fuming about the poor prototypes, the Taiwan units continued with their field tests of the German sun helmets quite enthusiastically. But after 5 years of happy use in the field, many helmets showed wear and tear. So on 14th of October 1920 a letter was received by the Minister of the Army from the Commander of the troops in Taiwan to the effect that they needed 3,411 additional quantities of the German helmets to replace damaged ones and expand the wearing of these helmets to all its officers and men.

    To this request, army headquarters replied that though no further helmets could be supplied at that time, design work was progressing on the IJA’s own model and prototypes should be forthcoming for definitive testing within the coming year, 1921.

    What the army headquarters forecasted as definitive testing became a large scale test indeed, as it became the army’s first full scale tropical uniform test, producing a report of nearly 300 pages.

    Prototypes sent to reach Taiwan by 10th of June 1921, included (1) 3 different sun helmet prototypes, (2) 3 styles of pants, (3) undershirt and underpants, (4) anti-mosquito gloves and masks, (5) waterproof coat, (6) waterproof poncho, (7) back sack, (8) 2 types of socks, (9) 2 types of boots, (10) linen leg wraps, and (11) two types of overcoats.

    The overall mission statement said the immediate purpose was to contribute to the summer uniform designs for troops in Taiwan and Central China, with a further view to laying a general groundwork for studying the clothing requirements of an army operating in the tropics. Tests were to be carried out both in the north and south of Taiwan to cover the subtropics as well as tropical conditions.

    The 1921 Science of Sun Helmet Design

    The final report was titled “Medical Implications of Tropical Uniform Design Studies conducted in Taiwan” dated October 1921.

    Collectors of WW2 German Africa Corps items like to point to the red color of the lining of the army’s tropical field caps and brag about the scientific development of the DAK uniform by the University of Hamburg, but such things were actually already “old hat” to the Japanese army more than 20 years prior to the German effort.

    Nowadays they seem to distinguish between sun stroke, heat stroke and heat exhaustion, but these problems were all loosely referred to as 喝病 (now a dead word in Japanese, read Katsubyou, which I will simply translate as “sunstroke” here not to split hairs), a problem the IJA had to deal with as part of common ailments associated with long marches.

    In the 43 years between 1896 and 1938, the Japanese Army and Navy combined had a total of 5,586 recorded severe cases, of which 172 cases led to death of the soldier. It was not a problem unique to Japan, as more than 700 New Yorkers were also reported to have died in August of 1896 when temperatures rose above 100 degrees Fahrenheit (38 degrees centigrade). Similarly, 304 people died in Detroit in July 1936 in a 7-day spell of over 100 degree heat. Detroit had only notched a total of 7 days of over-100 degree heat in the previous 62 years since 1871, so it was indeed quite murderous.

    The root cause was not fully understood at that time, but it was regarded as a combination of dehydration due to sweating and localized overheating of the brain tissue through radiation rays of ultraviolet, infrared or “Etwas (they used German for something)”, which penetrated hair, scalp and skull easily, but got fully absorbed by the brain. For these reasons, sun helmet design focused on obtaining good heat ventilation and blocking direct sunlight as well as the invisible rays that cooked your brain.

    The prevailing school of thought in the international medical world of the time was that ultraviolet rays were most to blame for sun stroke, but new experiments had just revealed the threat of infrared, which put a question mark on conventional thinking.

    The reason for using “red” or “green” for lining colors was because these colors were known even in 1921 to be effective against ultraviolet rays, but as new questions were being raised about infrared, some practical hedging became necessary, not to put all eggs in one basket.

    Common sense tells us now that white reflects heat waves while black absorbs them, so we are tempted to think simply that black should be avoided. However, actually the reverse could be true for headgear design. If black absorbed the energy, it is wonderful news for the human head underneath it, as long as this absorbed energy can be effectively dissipated by the headgear design without being transferred to the human. As a matter of fact, the research team noticed that the traditional summer headwear of the natives of Taiwan actually favored black, not white.

    Either way, the science of the times did not yet have conclusive answers, so they had to test to cover all bases. But one thing for certain was that heat had to be dealt with within the space between one’s head and the ceiling dome of the helmet, so measuring temperatures there, by changing other variables like color and material, became the main exercise for the headgear team in the test.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  
    Last edited by Nick Komiya; 10-19-2016 at 08:41 AM.

  5. #5


    1921 Sun helmet Prototype testing

    300 Sun Helmet Prototypes were produced for the test, of which 100 had "felt shells”, 150 had “woven Panama hat shells” and 50 had “Gourd Sponge shells (also tested in helmet covers later in 1934)”. These were benchmarked against the standard army visor cap and also against the captured German Sun Helmet.

    Visor Cap vs German Sun Helmet
    It was already known that the visor cap was no match for the heat-insulating performance of the captured German sun helmets, but for instance, when the ambient temperature was 38 degrees, the helmet was cooler by 5.

    German Sun Helmet vs IJA Prototypes
    The main improvement the IJA wanted to achieve over the German counterpart was dry weight as well as water drenched weight, which was achieved by all three prototypes by a comfortable margin.

    Then in temperature comparisons throughout the day, the felt model bettered the German model. Beyond that point, it was a comparison between the 3 prototypes comparing impact of surface cloth colors, etc.

    They tested white, sky blue, natural unstained cotton and the military green in both tropical Tainan and subtropical Taipei.

    Sorry, but the data charts with temperature comparisons I originally put in here kept on falling out of alignment in the upload, so I had to remove them.

    In summing up, they concluded that the Panama version was the most comfortable in heat. However, because it seemed to let through a lot of invisible sun radiation, they claimed to feel a stinging pain at the top of the head when the sun was high.

    Felt came second in overall performance, but against blocking ultraviolet or infrared it was markedly better. Thus they said for Taiwan, “Panama” was the choice, but for more tropical climates, where invisible rays of a more intense sun could be expected to easily penetrate the panama shell, felt was thought to be a safer choice.

    Gourd sponge was quickly eliminated when it got all soggy in rain and also gave off an unpleasant smell in that state.

    In the latter part of the report it was revealed that what they referred to as “Panama” was actually a local Taiwanese Marsh Grass traditionally cultivated for weaving hats and baskets, and they further recommended Pandanus as also worth looking into, as they grew wild throughout the island in abundance which tended to produce a sharper looking product.

    This suggestion was probably taken up later, because the first official sun helmet of the IJA that appeared two years later called for this Pandanus, which was not covered in the 1921 testing.

    I only gave you the gist of the test results, but if you want more details, here is a spreadsheet summary from 1921 for you to study in detail.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  
    Last edited by Nick Komiya; 10-19-2016 at 01:12 PM.

  6. #6


    1923 August, IJA’s First Model Sun Helmet Introduced (Model 1923)

    The 1921 tests in Taiwan came to fruition in 1923, when the Army finally launched its official sun helmet design. There are no launch documents surviving, so it is not clear what the official designation of the sun helmet was at the time of its introduction, but judging by the lack of any Type designation even for the new steel helmet launched the previous year (star-vent/cherry blossom helmet), which was simply called a Provisional Standard “Kabuto” (head amour), I doubt that it got any designation like a Type 12 for the 12th year of Taisho (though the pistol that followed 2 years later became the Type 14).

    Later army specification books, show spec revision histories, so even without launch documents, one can tell that the first specs were finalized on 3rd August 1923.

    The drawing below is this first model IJA sun helmet, which I am likely unveiling for the first time in post-war history. This drawing must have been issued around 1927, judging by the sample markings, indicating the 2nd year of Showa, but spec revision history records confirm that no changes had taken place in between, so the 1923 helmet would have been identical to these drawings.

    Also of note is that the drawing now calls the sun helmet officially a 防暑帽 (anti-heat hat), no longer a helmet hat. That word change probably occurred in the 1923 launch. Chances are it was officially called a Provisional standard anti-heat hat (仮制式防暑帽) in the 1923 launch in the same manner as the steel helmet.

    Looking at the design, I cannot help being reminded of the “Man with the Yellow Hat” from the 1941 kid’s book, “Curious George” (“Coco – Der neugierige Affe” to Germans) and if this was supposed to be a refined design, one shudders to think what the “ridiculously ugly” first prototype from 1916-17 looked like.

    Compared to the WW2 model familiar to many collectors, the liner system is much more conventional like the style the Germans used in WW2 with a zigzag spacer as insulation between the helmet shell and the sweat band. Apparent is the lack of any vents with cover at the top, but 3 large grommets on each side instead as ventilation holes. Also the helmet was made in 3 sizes of small, medium and large unlike the later one-size-fits-all design. The material finally selected for the woven shell was initially leaves from Pandanus tectorius, known in English as the Tahitian Screwpine.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  

  7. #7


    1928 Jan. “Made in Taiwan”

    The Army in Taiwan not only got to test the helmets, but was finally made to supply them as well. In the end, there is a sense of “tribal wisdom” in this making of tropical wear from locally available, time-tested native materials.

    However, another tweaking was now necessary to make sun helmet production in Taiwan a truly viable proposition. This adjustment was the reason behind the spec revision dated “31st January 1928” in the spec revision history.

    The army in Taiwan was required to supply 31,700 woven shells to the main depot by 15th February of that year, but material and labor availability was jeopardizing this order from the mainland.

    The Pandanus (林投) leaves specified as material in the 1923 specs were not material available on any constant commercial basis, but something that the Taiwanese natives went out to collect when orders for sun helmets came in from the IJA. The plant was growing wild on the island and thus available in almost unlimited quantity, but processing of the leaves after harvesting involved extensive drying under the sun, which made such work in the rainy season impossible, because there were no indoor drying facilities.

    On the other hand, what they had called “Panama” in the 1921 testing was actually what the natives favored for their own weaving. It was a plant called 大甲藺 (Tai Koui), a tall grass growing in marshland with the Latin name of Scirpus triqueter, (it has no English name, so I will call it Taiwanese Marsh Grass).

    This grass was used traditionally to weave into hats in Taiwan and the local industry already had a capacity to produce 501,000 hats annually, supported by a commercially grown crop of the grass. They cultivated the grass by sowing seeds in January, which yielded two harvests in July and December.

    Better yet, for this product, the island already was home to approx. 45,000 weavers, so if the sun helmet material could be switched to this grass instead of Pandanus leaves, immediate increase in production numbers could be achieved.

    Pandanus was a much stiffer material to work with, so the existing labor force of grass weavers couldn’t be readily switched to work with the new material, unless given a period of adjustment for relearning the craft in the new material.

    The Taiwanese marsh grass involved no disadvantages in weight or strength, and the only drawback of a tendency to grow mould, due to the humidifying needed before weaving, could easily be dealt with by drying the woven shells after completion.

    Thus in January 1928, Taiwanese grass became accepted as an alternative shell material to Pandanus and slight changes to the specs were made to accommodate this alternative material.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)   The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  

  8. #8


    1930 May, Launch of the Second Model Sun Helmet Showa 5 Type (昭五式)

    7 years after the introduction of the IJA’s first sun helmet, a revamp of design was signed off by Emperor Hirohito on 14th May 1930. A whole new range of items got launched at the same time like new canteens, back packs, bread bags and the army jacket now got a vertical seam in the back to rationalize production efficiency.

    The external appearance of the sun helmet did not change hugely, but instead of having a third vent grommet on each side, a top vent with cover was revived.

    The shell material was now either felt or woven Pandanus (to also include Taiwanese marsh grass). The shell most certainly must have now been reduced to one size as the spec descriptions talk of "internal provision for size adjustments between large and small". However, the shell shape did not yet conform to the profile of the Type 90 helmet that got launched later that year on 28th October, so the sun helmet did not seem to include wear over the helmet yet.

    You may question why I do not simply call it "Type 5", instead of "Showa 5 Type". That is simply, because the army itself insisted on calling it the Sho-Go Shiki (“Sho” being abbreviation for the era name of “Showa” and “Go” meaning 5). So “Sho 5 Type” is the direct translation, but that won’t make sense to Westerners, so I used the full word Showa
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  
    Last edited by Nick Komiya; 10-19-2016 at 01:15 PM.

  9. #9


    1937-1938 Prototype Tests in Taiwan

    Once again, after 7 years of using the Type 5 sun helmet, another revamp was in the works. Again a whole lineup of items were to be tested, but the 120 sun helmets shipped from the main depot to reach Taiwan by early June of 1937 aimed at reducing weight and increasing water repellency and sun protection.

    Tests were to be conducted again for two summers in 1937/38. The shell material was now a combination of bamboo, cotton wadding and thin balsa sheeting. They seemed also to have tried out the new shell design, shaped like the Type 90 steel helmet already in 1936, but this time improving it further by removing the raised ridge from the edge of the brim to allow rain to flow off more smoothly.

    As the new steel helmet profile greatly reduced the size of the rear brim, they also tested a removable 3-section neck flap similar to the 4-section ones used on field caps to be hung at the back of the sun helmet (a much simpler solution than the earlier flip-up rear visor or the samurai armor style collapsible visor suggestion).

    1938 June, IJA’s Third Model Sun Helmet Introduced (Type 98 Version 1)

    The Type 98 (for the year 2,598=1938) army uniform series was launched on 1st June 1938, and the Spec description for the Showa 5 Type was now changed to have the shell material specs to read “Bamboo, Felt or Pandanus or similar (Taiwanese Marsh Grass)”. Thus material alternatives had increased.

    However, in spite of the expanded material choices, the Army in Taiwan still remained responsible for supplying the bulk of the sun helmets, as one can read in a memo dated 28th January 1938, ordering them to supply 110 thousand woven shells to the Hiroshima depot by end of March. This was in addition to the further 40 thousand sun helmets to be completed locally in Taiwan for keeping in stock there.

    The new sun helmet design had a profile matching the Type 90 helmet and it was designed so it could be worn alone or also over the steel helmet. When one wore it over the steel helmet, one was supposed to remove the size adjustment cord inside the sun helmet and by running the cord through 3 corded eyelets placed on the inside rim of the sun helmet, it was to be secured to the 3 chin strap fixing-rings inside the steel helmet.

    The official description says one could also wear a neck flap on this sun helmet. However, though they had field-tested neck flaps in the previous year’s tests, there is no sign of special flaps for the helmet having been launched, so one can only assume that the flap for the field cap was also expected to be adapted for use on the sun helmet.

    Interestingly, the model 98 series also included the army’s first model helmet cover, so it means that two alternative means of preventing the helmet from baking under the sun were offered at the same time, helmet cover or sun helmet. The ventilation grommets and the lidded top vent were carryovers from the Showa 5 Type, but these would gradually be eliminated in the following years, giving a total of three configuration variants of the Type 98 sun helmet by 1942.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)   The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  

    Last edited by Nick Komiya; 10-18-2016 at 10:07 PM.

  10. #10


    1938 Nov.-1939 Nov. Testing of two further alternatives for shell material

    Even before the official launch of the Type 98, a memo dated 25th May 1938, already revealed the army’s plan to test out alternative shell material.

    Because of the massive mobilizations since the breaking out of the China Incident in 1937, Japan was being faced with severe material shortages of everything and the army had to expand its manufacturing options even if it meant compromising on performance.

    This time, among the tropical gear shipped to reach Taiwan by end of June were 75 pieces each of two types of sun helmet prototypes. The troops were to test them again for two summers and report back each November.

    ” Type A ” had a woven bamboo shell which had insulation material sprayed onto it. Artificial leather straps were used for the liner and the two side vents were omitted, leaving only the top vent.

    “Type B ” on the other hand, had the side vents, but omitted the top vent instead, and the shell material was thin wooden sheets combined with “Sanada” tape with mixed insulation material. “Sanada” referred to a woven tape usually called Sanada Cord, used for straps for armor and swords, an invention stories credit to a famous war lord, Yukimura Sanada (thus the name).

    They used this tape material in a spiraling pattern to shape the shell. The result report is missing from the archives for this test, but Sanada tape was definitely added to the spec list and the side vents were omitted from 1941 as you will see soon.

    It is most likely that they added another shell variation to be tested in the second summer testing for 1939, as official spec revision history records the addition of chocolate vine as of 6th February 1939.
    Click to enlarge the picture Click to enlarge the picture The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)   The Evolution of the Japanese Imperial Army Sun Helmet (1915-1945)  

    Last edited by Nick Komiya; 10-18-2016 at 10:11 PM.

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