The Type 97 Chi-Ha "Long Gun": Tank Destroyer or Something Else?

      Following the capitulation of Japan on August 15, 1945, the first U.S. personnel flew into Atsugi Kaigun-hikōjō (Naval Air Facility Atsugi), Kanagawa Prefecture on August 28, 1945, starting the occupation of Japan that lasted until April 29, 1952. As was the case following the end of the war in Europe, the U.S. had a keen interest in gathering up any and all military technology that the Imperial Japanese Army and Imperial Japanese Navy had been using but more importantly, had been developing. Intelligence teams fanned out across Japan and one such group was deployed to the Tateyama Naval Gunnery School which was located in Tateyama, Chiba Prefecture.

     Founded on June 1, 1941, the Tateyama Naval Gunnery School was a branch of the Yokosuka Naval Gunnery School. Whereas the latter school instructed pupils on operating and servicing guns utilized on naval ships, the Tateyama Naval Gunnery School taught students how to conduct land warfare, amphibious landing operations, and even airborne (paratrooper) training. As part of such training, anti-tank tactics had been included and as the U.S. intelligence team roamed the school, they found a most intriguing piece of anti-tank weaponry sitting on the grounds.

     The Japanese, for a number of reasons, were very late in the game of developing potent tank destroyers. The main reason for this, and which also stymied tank development, was that early on, the Japanese rarely faced enemy armor that was either deployed effectively, employed in any real numbers, and in some cases, did not pose a serious threat. Other factors included not facing enemy forces that fielded much in the way of other anti-tank weaponry (such as anti-tank rifles and guns), jungle terrain that dominated much of the Japanese holdings did not favor armor, and since the Japanese relied on naval transports to send troops and equipment around the empire, this was a limitation in building heavier tanks. As 1943 wore on, the Japanese were encountering Allied tanks such as the M4 medium tank that proved quite a problem for Japanese tanks. Only the Type 1 47mm gun could offer some challenge to the M4 and this started to equip the Type 97 Shinhoto Chi-Ha (“New Turret” Chi-Ha) in 1942 but even then, the M4 was relatively immune to the Type 1 frontally. The Japanese responded with the Type 1 Gun Tank Ho-Ni I tank destroyer which was fitted with the more potent Type 90 75mm gun. Although production started in 1942, the Ho-Ni I did not see action until 1945. The successor, the Type 3 Ho-Ni III, was fitted with the same Type 3 75mm tank gun as used on the newer Type 3 Chi-Nu medium tank. Under forty examples were built starting in 1944 and were not deployed outside of the Japanese main islands. The Japanese had other tank destroyer designs, some of which made it to a prototype stage. The final tank destroyer design, the Type 5 Na-To, was to replace the Type 3 Ho-Ni III. Built upon the Type 4 Chi-So medium tracked carrier, the Na-To was fitted with a Type 5 75mm tank gun which was used on the Type 4 Chi-To medium tank. Given the state of Japan's industrial complex, only two Na-To were built and though 200 were ordered, the type never entered production.

     What U.S. intelligence personnel saw at the Tateyama Naval Gunnery School is, to this day, debated on what exactly the vehicle was. Was it a tank destroyer prototype? Was it something that was created by personnel at the school as a ad-hoc vehicle to defend the facility? Was it simply a mobile test bed for the gun? What we do know is that the massive gun was the Type 10 120mm anti-aircraft gun. Developed in 1921, the gun entered service in 1926 and was fitted on Japanese aircraft carriers (namely the Akagi and Taiyo classes), cruisers (such as the Aoba, Yubari, and Myôkô classes), and other naval ships. The Type 10 was improved and remained in production from 1942 to 1945. The chassis the Type 10 was fitted to was the Type 97 Chi-Ha medium tank, one of the more common Japanese tanks of World War II. 

     The Type 10 had a weight of 2.9 tons, a uniform twist 34-groove barrel, with an overall gun length that was 18.3 feet long. The lightest single barrel gun mount, as used on some cruiser classes, was 7.7 tons. However, the gun was also used from fixed ground positions and the mount utilized was simpler and lighter than the ship mounts. The Type 10 fired two types of HE (High-Explosive) ammunition, an incendiary shrapnel round, and a illumination round among others. The ammunition used was fixed with a complete HE round being 3 feet long with an all up weight of 75 pounds. Muzzle velocity for the HE ammunition was between 2,707 to 2,723 feet per second and this gave a maximum range of 9.9 miles with the barrel at a 45 degree elevation. Other aspects of the Type 10 included a horizontal sliding-wedge, semi-automatic breech with a hydro-spring recoil system. A skilled gun crew was able to manage 10 to 11 rounds per minute but the average rate was more often 6 to 8 rounds per minute.

     The Type 97 Shinhoto Chi-Ha had a weight of 16 tons total with a length of 18.1 feet. The image of the vehicle is a still from a film and is the only existing image available. It is a certainty that U.S. intelligence took photographs of the vehicle to document it but those photographs have yet to surface. From it, we can deduce several things. The first is the Type 10 is actually longer than the tank itself. The turret was, obviously, removed and the superstructure (upper hull) of the tank was cut away to reduce the height and provide a more flat firing platform. The gun is facing to the front of the tank and it is using a very cut-down version of the mount most often used when the gun was deployed from static positions. By consequence, the elevation of the Type 10 is severely limited though this isn't much of a concern if being used in the anti-tank role. The gun is showing some depression ability, likely no more than 10 degrees. There appears to be some form of crude gun shielding on the sides of the mount and on the front on either side of the gun tube. Other than this, the gun crew operated the weapon from the rear engine deck without any other protection from shrapnel or small arms fire let alone having no protection from the elements. There also appears to be a muzzle brake fitted to the end of the barrel as a means to reduce the recoil. The weight of the gun and gun mounting is evident by how compressed the suspension is on the tank. Given the size and weight of the ammunition, likely only a handful of rounds could be carried on the vehicle itself and assuming it entered service, either it was to be fitted with a trailer to carry additional ammunition or a support vehicle had to accompany the tank destroyer in the field to transport both the crew and ammunition. A anti-tank round was never developed for the Type 10 and the HE ammunition had between 3.75 to 4.1 pounds of explosive in the warhead. This was similar to the postwar Soviet 130mm KS-30 anti-aircraft gun, lighter than the German wartime 128mm Flak 40 which had a 7.5 pound explosive warhead, and also lighter than the U.S. 120mm M1 anti-aircraft gun. How the HE round would have been effective against Allied armor is unknown. Certainly a tank being hit by such a round would suffer ill effects. For example, the Soviet SU-122 assault gun utilized the 122mm M-30 howitzer that fired a HE shell with 8 pounds of explosive in the warhead and this was enough to demolish German tanks via concussive force upon a successful hit. Of course, how accurate the Type 10 would have been is debatable and it is doubtful it would have enjoyed any sort of accuracy beyond 1 mile. Another issue that is brought up is exactly how long the Type 97 chassis would have bore up to the recoil forces of the Type 10 before stress fractures appeared in the tank chassis. The additional weight of the gun would certainly have taxed the 170hp Mitsubishi SA12200VD diesel engine, reducing the 24mph speed of the standard Type 97 tank which would make “shoot and scoot” tactics difficult. In addition, the hull armor of the Type 97 was 25mm in the front, 26mm on the sides, and 20mm in the rear which was totally inadequate against any Allied tank gun. This would have forced the crew to fire at range, with the likely inherent inaccuracy, in order to be able to relocate before return fire is received.

     To this day, it remains unknown what happened to the prototype following the discovery of it and, as already stated, exactly what its purpose was also remains a mystery.

Primary Sources:

DiGiulian, T. (2020, October 9). 12 cm/45 10th Year Type. Navweaps. Retrieved December 19, 2021, from http://www.navweaps.com/Weapons/WNJAP_47-45_10ns.php 

Johnson, Curt Artillery (London: Octopus Books, 1976)

Aimo Allan Koivunen: The Soldier Who Overdosed in Combat

     Thanks to the Facebook algorithm, a story floated through my feed about one Aimo Allan Koivunen, a Finnish soldier who supposedly went on a drug fueled escapade across the Finnish landscape, pursued by Soviet soldiers in March 1944. Having seen such news stories be wrong before, I decided to take a deeper dive and see if there was, in fact, any truth to the wild adventure of Aimo Koivunen. Turns out, it was true!

     Aimo was born on October 17, 1917 in the Finnish town of Alastaro. His father was Frans Vihtori Koivunen and his mother Aune Sofia Koivunen. He had at least two sisters (Eila Ilona Aalto and Marjatta Koivunen) and two brothers (Tapani Vihtori Koivunen and Väinö Armas Koivunen). After his baptism in October 24, 1917, his godparents were Frans and Olga Heikkilä, a farming family. At some point in time, Aimo married Elsa Esteri. At least in the sources I have available, little is said about his early life prior to entering military service. 

     When the Winter War against the Soviets started in November 30, 1939, Aimo was already in the military, being assigned to the third battalion of Jalkaväkirykmentti 13 (III/JR 13; Infantry Regiment 13). This battalion was made up of Finnish Home Guard men from the Salon Suojeluskuntapiiri Sammatissa (Salo Conservation District in Sammat). Aimo served with the unit until May 27, 1940 (the actual combat ceased on March 13, 1940). With the prospect of war with the Soviets again on the horizon, Aimo was transferred to the sixth battalion of Jalkaväkirykmentti 35 (6./JR 35) on June 17, 1941. The Continuation War commenced on June 25, 1941 and Aimo went to battle with the battalion until July 19, 1942. After this date, there is a gap in Aimo's service history when on October 28, 1942, Aimo is listed with the fifth battalion of JR 35 (5./JR 35) until January 9, 1943 when Aimo was reassigned to the headquarters of JR 35 until April 30, 1943. On that date, Aimo was transferred to Osasto Paatsalo, Erillinen Pataljoona 4 (Department Paatsalo, Seperate Battalion 4; 4./Er.P 4).

     Er.P 4 was a special unit established on July 1, 1943 to conduct long-range patrols for the purposes of intelligence gathering on Soviet forces. The battalion was broken down into four companies, or departments, which were Osasto Vehniäinen, Kuismanen, Marttina, and Osasto Paatsalo. A fifth department, Osasto Jauri, was set up in May 23, 1944 as a transport flight for the men of the other companies. Each department was responsible for covering assigned sectors within Finland proper. 4./Er.P 4 was responsible for the eastern border of Finland stretching from Kiesting to the Arctic Ocean. Osasto Paatsalo had actually existed prior to the formation of Er.P 4, first commencing patrol activities during the Winter War. Until June 1944, 4./Er.P 4 was commanded by Kapteeni (later Majuri) Harri Paatsalon. His successor was Kapteeniluutnantti Pentti Ahola.

     On March 10, 1944, Aimo was part of a ski patrol led by patrol leader Luutnantti Norri near Kantalahti, Lapland. The overall mission was commanded by Vänrikki (2nd. Lieutenant) Rytkösen. While moving along a road during the evening, the patrol penetrated Soviet lines and a shot was heard followed by an aircraft flying overhead. The patrol thought that they had avoided the Soviets but they soon ran into a Soviet ski patrol that took the Finnish under sub-machine gun fire. Rather than engage the enemy,  Rytkösen ordered his men to withdraw. The Soviets continued to bear down on the retreating Finnish who returned fire which gave the Soviets pause. In the brief respite, Aimo was ordered to deploy mines to slow the enemy advance. Unfortunately, he got no fire support from his men to the point that he enlisted villagers from Välikankaan to keep watch for the Soviets. It was decided that if need be, the patrol would rendezvous at Kaitatunturi then continue on to Koutamotunturi to link up with another Finnish patrol led by Ilmari Honkanen.

     All told, the skirmish with the Soviets that the patrol had run into lasted ten minutes. Still, the Soviet ski troops hadn't given up the chase and although both sides exchanged fire, none of the Finnish troops were hit. As the patrol continued to withdraw, Aimo was able to seed mines along the tracks they had been using and which they expected the Soviets to follow. After several hours, Aimo and the rest of the patrol were exhausted, having been engaged for several hours but fortunately, the Soviets had stopped following them. Aimo, especially, was feeling weak, in part due to having had little to eat. He then remembered that in his tunic pocket, he had the entire patrol's allotment of Pervitin.

     What was Pervitin? It was a methamphetamine. When taken, it resulted in increased energy, reduced the need for sleep, lowered hunger cravings, and instilled a sense of immense, nearly unstoppable, confidence in the imbiber. In Germany, Pervitin was able to be purchased over the counter until 1941 when it became regulated. Soldiers were issued the drug in 3 milligram tablets, tank crews had their own version in “Panzerschokolade” (“Tank Chocolate”) which was Pervitin laced chocolate candy, while the Luftwaffe issued it to air crews to enhance their attention span but also to allow downed airmen to sustain themselves while making their way back to friendly lines. Pervitin was made illegal in 1941 but this failed to stop the flow of the drug and in fact, the German military seemed to turn a blind eye to its use despite the very real problems of addiction, overdose, withdrawal effects, and obfuscation of the senses when it came to military decision making. Like the Germans, the Finnish (as did the U.S.) also issued it to their troops to enable them to push themselves beyond their regular limits.

     Aimo, feeling the effects of exhaustion, took the bottle of Pervitin out of his tunic and attempted to shake a pill out of it to consume. Try as he might, the pills stuck together and would not come out. Aimo shook the bottle and the entire supply of pills, thirty in all, fell out into his gloved hand in a clump. Out of sight of his comrades, he downed all thirty pills at one time. In minutes, the Pervitin took effect and Aimo felt flush with energy but in taking such a massive quantity, Aimo's perception soon began to warp and he felt as if he was going to pass out. His last, unfazed thought was that he had made a terrible mistake.

     Aimo recollected that when he recovered his wits to a degree, he was at the Finnish border, alone. He was unsure if he abandoned his patrol or if his patrol abandoned him given his state. It was March 19 or March 20, 1944. Aimo was in for another shock in that not only did he not have his sub-machine gun, his backpack was totally empty. Thus, he had neither food, water, nor any change of clothing or other supplies that he had originally carried in the pack. Outside of what few items he had in his uniform pockets, Aimo was only armed with a knife. Aimo also still had his wrist compass and made for what he thought was Koutamotunturi. Along the way, he spotted the smoke from campfires in the distance. Believing it to be his comrades, Aimo skied on, using a steep slope to pick up speed. As he closed the distance, to his horror, the campfires were not surrounded by Finnish troops but Soviet ones. Originally starting to brake thinking they were allies, Aimo stopped braking and used his remaining momentum to roar right through the Soviet camp. Startled Soviet soldiers scattered as the Finnish soldier flashed through them. The return fire once the Soviets got over their surprise was ineffective. However, Aimo was not out of the woods when a ski patrol of skilled Soviet partisans picked him up and gave chase. It took everything for Aimo to keep ahead of the partisans, the distance sometimes being only 328 feet between the two opponents. Aimo came to the base of a mountain and as the snow was not as packed, it caused his skis to sink. He struggled to get up the mountain, the partisans getting as close as 65 feet. By the time Aimo crested the mountain, he managed to again put distance between him and his pursuers. By a stroke of luck, a snow storm blew in which reduced visibility to only a few feet. The storm, coupled with the coming of night, saw the partisans abandon the chase.

     Aimo spent the next day skiing to the west before he stopped and set up a campfire, managing a tea from a packet that he had found in his pocket. After the tea, he used his hands to dig out a pit to get into and sleep. Rising in the evening, Aimo continued, scooping up pine cones along the way and putting them in his backpack. With these, he made a soup for sustenance as he carried on with his trek. At one point, he had to fend off a wild wolf with his knife but in the fight, his wrist compass was broken. As Aimo went on, at some point, his backpack was lost. By now, he had been moving for days, driven on by lucid dreams of his comrades. As he traveled, Aimo came upon a small shack and after going inside, he set up a small fire on the floor, using a tin cup he found to warm snow into water. Likely due to his state of mind, Aimo was not at all shocked when the shack started to catch fire. As the fire spread along the wooden floor, Aimo simply shifted further away, trying to sleep. Eventually, the entire shack burned to the ground and Aimo simply carried on, moving to a sauna near the shack, starting a fire there until he was able to sleep. Without his compass, Aimo navigated using the North Star. To add to his discomfort, the fingers on one of his hands were beginning to succumb to frostbite. 

     Aimo found a well-used trail and road that led to a German position. There were dugouts and barbed wire emplacements but while Aimo called out, there was no answer. Unhitching from his skis, Aimo walked into the position and then stepped on a anti-personnel mine with his left foot. The resulting detonation shredded his foot and lower left leg. So as not to freeze, Aimo crawled towards the nearest dugout. With a ski pole in his left hand, he reached the dugout and with his right hand, grabbed a door handle to the entrance into the dugout's covered section. He passed out, the handle having broken off the door. When he awoke, Aimo used his knife to carve wood chips out of the door to make a small fire with and used the tin cup to melt snow to drink. Aimo remained there, in and out of delirium, the only food coming from a jay bird that came within grasping distance. Aimo ate it raw. After seven days, an aircraft flew overhead and Aimo put a scrap of his snowsuit on his ski pole and waved it around. Fortunately for Aimo, the aircraft was Finnish and the pilot noticed him and waggled the plane's wings in acknowledgment before it flew away. In time, a Finnish patrol arrived and evacuated Aimo to a field hospital in Salla. Upon arrival, Aimo's heart-rate was 200 beats per minute which was well over the average 60 to 100 beats per minute and his weight was down to 94 pounds. He also survived temperatures of 20 to 30 below zero. In two weeks, Aimo had skied from Kaitatunturi to the abandoned German position some 30 miles north of Salla for a total distance of 248 miles.

     Aimo survived the war, being discharged on April 1, 1944. He ended the war with the rank of Alikersantti (Corporal). The photograph of Aimo shows him with, most likely, the green with white border collar tabs of the infantry. Because the collar tab is devoid of any stripes, the rank shown in the photograph is that of Sotamies, or Private. If he had his Alikersantti rank at the time of the picture, there would have been a single yellow chevron, running vertically, in the center of each tab. The medals on his right upper tunic pocket are skill badges. The top row consists of a unidentified skill badge while the one nearest the tunic buttons is a grade of  the Ampumamerkit (Shooting Badge) for Kivääri (Rifle). The badge centered on his pocket is the Vartiotehokkuusmerkki (Civil Guard Efficiency Badge).

     Aimo passed away on August 2, 1989 at the age of 71 in Jyväskylä, Finland. He was laid to rest in Pylkönmäki.

Primary Source:

Koivunen, Aimo (1978, April 14) Pervitiini-Partio, Kansa Taisteli, 126-132.