Technical Manual, U.S. War Department, October 1, 1944
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Chapter IX: Weapons
Section IV: Tanks and Armored Cars
1. GENERAL. Until 1929 Japan did not produce any tanks (Sensha) of her own. As usual, her ideas were borrowed from the West, particularly from the British and French, and her first tanks were versions of early Renault, Vickers, and Carden-Lloyd models. Later she turned to Russia for new developments. Prior to 1941 the Japanese had every opportunity to study the experience of the Allies in war, and it is also reasonable to assume that they are still borrowing freely from other nations. What influence German design will have on future Japanese tank production is still to be seen. During 1935-37 the Japanese apparently were concentrating on tankettes, light tanks, and medium tanks, perfecting one model in each class. It is probable that a few heavy tanks also were produced. Their tanks fall into four main types, divided according to weight. These are:
a. Tank nomenclature. For purposes of general information, annotated photographs illustrating various items of tank nomenclature, are reproduced in figure 239.
b. Horsepower. Horsepowers indicated throughout the following text are all Japanese ratings. In each instance, where engines have been examined (e.g., M 2595 Light Tank and M 2597 Medium Tank) it had been clearly shown that they are capable of developing a considerably greater degree of power than that reported. Consequently, wherever possible, theoretically indicated horsepowers, derived from computations based on engine specifications, have been shown.
c. Crews. Crew compartments so far examined are limited in size, and little attention has been given to comfort. The turret and hulls, however, have been found to be well insulated with material such as asbestos.
d. Armament. In the light and medium tanks, relatively low velocity 37- and 57-mm guns are used. There is also evidence that a 47-mm gun is used in medium tanks. Although a machine gun is normally mounted in the rear of the turret, and is of some tactical use, it is doubtful if the main turret weapon and rear machine gun can be fought at the same time. The use of armored sheaths is standard for all machine gun barrels. All machine guns are ball mounted, and the main turret armament has a limited traverse, independent of that of the turret. In both the light and medium tanks a hull machine gun is mounted.
e. Armor. Japanese tanks, so far examined, have been lightly armored, but the plates tested have been of good quality. In the arrangement of armor, use has been made of deflection angles, but not to any considerable degree. In many cases reentrant angles have been formed, but no steps have been noted to protect turret rings or mantlets against jamming or splash.
f. Engines. Diesels are mainly used.
g. Suspension. In all these models the same basic suspension is used. This consists of bell-crank arms carrying rocking pairs of wheels. These arms are sprung by horizontal suspension springs, protected by armored casings.
h. Vision. Little use has been made of periscopes, etc., vision being dependent on slits, occasionally backed by a glass block.
i. Doors. The question of escape in case of fire or other emergency has received little attention.
j. Communication. As far as known, radio is used only on the basis
k. Insignia. Army tanks have a 5 point star mounted on the front, while navy tanks have the anchor insignia. Many tanks either fly or carry the national flag as an identification sign. Naval tanks usually have the small naval insignia painted on the sides.
l. Future developments. (1) General. It would be dangerous to measure Japanese tanks by models now known to exist. Evidence exists that Japan is in close touch with German development, and it may well prove that Japanese tanks will show considerable German influence. That Japanese tank design is not stagnant is clearly indicated by the recently captured new type amphibious tank described in this section. In this particular tank the coaxially mounted machine gun is considered of significance. Hitherto, there has been no evidence that the Japanese have mounted weapons in this manner, so it must be considered indicative of a new trend.
(2) Armament. High velocity antitank guns, of at least 75-mm caliber, and modern high performance armor piercing high explosive ammunition, as well as hollow charge types, may be expected. As a temporary measure, earlier model tanks, such as the medium which mounts a 57-mm gun, could be given a new lease of life in a tank vs tank role by providing hollow charge ammunition.
(3) Armor. Early model tanks may be fitted with additional plates at vulnerable points; modern tanks can be expected to have heavier armor. Armor angles can be expected to receive more attention.
(4) Performance. So far Japan has used high power weight ratios. If these are maintained, high speeds and good cross country mobility will result. Suitable preparations, depending on tactical roles, may be undertaken to increase fording ability.
(5) Communication. Radio may be introduced down to individual tanks.
(6) Other improvements. Special items, like vision aids, escape facilities, and gun fume extraction may be developed. As an illustration of the trend in tank improvements, in the new type amphibious tank, many of the objectionable features of the older designs have been overcome. Reentrant angles have been eliminated, while the hull design has been simplified and welded construction used throughout. In addition, firepower has been improved by the substitution of a higher velocity 37-mm weapon and the coaxial mounting of a machine gun.
(7) Heavy tanks. The Japanese are capable of designing an efficient, modern, heavy tank, but it is thought that they may have difficulty in its quantity production. In the past the Japanese have produced a number of heavy tanks which must now be considered obsolete.
m. Miscellaneous types. Reports suggest that Crane, Repair, and Supply tanks may exist. These are believed to consist basically of a tank chassis, less the turret, and fitted out according to requirements.
2. TANKETTES. a. Tankette model 92 (1932). Development of the tankette has been progressive. In China it was used on a wide scale by Japan in a cavalry and reconnaissance role. In addition it is employed for towing tracked trailers carrying supplies and ammunition. Both welded and riveted construction are used throughout the hull (fig. 240). The suspension is an early Japanese development. Four point suspension of the hull is achieved by use of bell cranks, resisted by armored compression springs on each side. Four rubber tired bogie wheels, two return rollers, and outside center guide tracks are used. Front sprocket drive and left rear mounted engine are employed.
b. Tankette model 94 (1934). This tank embodies the general design of the original tankette (fig. 241). The rear idler has been replaced by a trailing idler, while the drive sprocket has been lowered accordingly. Suspension: bell crank, with armored compression springs. Rubber tired bogie wheels, and two return rollers are used. The engine is reported to be a four cylinder in line Ford tractor motor of 32 hp. Steering is the clutch brake principle.
c. Tankette model 97 (1937). Various specifications have been reported for a tank of this size (fig. 242). It is not certain if these refer to several different models of the M2597 or whether they relate to an even later model, the M2598 (1938). The suspension of this tank remains unchanged from that of the M2594 tankette. The hull, however, has been completely redesigned. More room has been provided in the turret to accommodate the 37-mm tank gun. As an alternative, a machine gun sometimes is mounted in place of the 37-mm weapon. Particular attention has been paid to a more simple design of the front plate and improved deflection angles. This tank is powered by a 4 cylinder, in line, air-cooled Diesel engine of 48 horsepower. Engine specifications indicate, however, that this engine would theoretically develop 105 hp at 2000 rpm.
3. LIGHT TANKS. a. Light tank model 93 (1933). This tank (fig. 243) represents the early development of the light tank series. The box type hull is divided into three compartments. The center portion is the fighting compartment, the superstructure of which overhangs the tracks. The right hand side at the front of the fighting compartment is extended forward to form a sponson for the ball mounted machine gun. The driver sits left, while the hull gunner sits right, in the forward compartment. The 6 cylinder gasoline engine is mounted to the rear of the hull. The suspension consists of six small, rubber-tired bogie wheels mounted on three semielliptic springs on each side. There are three return rollers. Front sprocket drive and center guide track are employed. The turret mounts one machine gun to the front, while some photographs show another mounted in the rear. Traverse 360°.
b. Light tank model 93 (1933) improved. Probably produced in 1933-34, this tank is an improved model of the M2593 in that the suspension has 4 bogie wheels coupled together in pairs via transverse even lever. It is not clear whether the apex is mounted to the hull by means of a bell crank or a stub shaft. Likewise it is not clear whether the armored compression spring is used at this stage of development. Two return rollers are used, as well as front sprocket drive. The hull of this vehicle is almost identical with that of the previous model.
c. Light tank model 95 (1935). In production from 1935 to at least 1942, there is a great deal of evidence to show that Japanese light tank design was frozen in 1935 to produce large numbers of these tanks (fig. 244). The hull has been completely redesigned. The suspension has been improved to utilize the bell crank and armored compression spring. The tank is powered by a 6 cylinder in-line air-cooled Diesel engine. The hull is constructed over an angle iron frame, with backing plates at the corners; insulation is provided by layers of woven asbestos. Ammunition for the 37-mm tank gun is carried stored in clips and racks in the fighting compartment. Two types are known. Model 94 shell—presumably HE of 1934 model, and model 94 AP shell—presumably APHE of 1934 model. 1170 rounds of 7.7-mm ammunition are stored in magazines just below the hull machine gun. 1800 rounds are carried in the fighting compartment for turret machine gun.
d. Light tank, "Keni." It is considered that this tank is not an obsolete model; it probably has been produced subsequent to the M2595 light tank. The 47-mm gun is a significant feature.
4. MEDIUM TANKS. a. Medium tank model 89 A (1929). This tank (fig. 245) is characterized by its box type hull, short front plate with door to the right, vertical front plate above this with hull machine gun mounted to the right, and small cupola hinged to top of turret. Five small return rollers are mounted along a girder. There are 9 small bogie wheels. The leading bogie wheel is independently mounted, while protective skirting all but covers the suspension. This tank is rear sprocket driven and powered by a gasoline engine. There is a rear turret machine gun, while the main armament is a 57-mm low velocity gun. Traverse 360°.
b. Medium tank model 89 B (1929). Also reported as the M2592 (1932), this tank (fig. 246) differs
c. Medium tank model 94 (1934). Probably produced in 1934 in quantity, this tank (fig. 247) has been extensively used in China. Comparison with the M 2589 models A and B shows that the return rollers have been reduced to four, the girder has been removed, and the skirting redesigned. The long front plate has a door on the left, above which is mounted the hull machine gun. The driver sits to the right. The Diesel engine has been increased to 160 brake horsepower. With the above exceptions the M 2594 is practically identical with the M2589 B. This tank is often seen with a ditching tail.
d. Medium tank model 97 (1937). Probably produced in 1937-1940. Some of the design features of this tank (fig. 248) are directly due to lessons learned from tankette and light tank construction. The four central bogie wheels are paired and mounted on bell cranks resisted by armored compression springs. Each end bogie wheel is independently bell crank mounted to the hull in a similar manner. There are three return rollers, the center one carrying the inside half of the track only. Backing plates are used to reinforce hull joints and corners. Numbers of these tanks are known to have been used in Burma. Other specimens were encountered on Guadalcanal.
e. Medium tank (unidentified). Probably produced in 1939, this tank is believed to have been employed on Corregidor. Its identity (fig. 249) has not been confirmed. With the exception of the turret and main armament, it is basically the same in design as the model 2597 medium tank. The turret has been improved to accommodate a modern high velocity gun, believed to be of 47-mm caliber. As usual there is a rear turret machine gun. The long overhanging rear portion of the turret would therefore provide more room for the simultaneous firing of both these weapons. With the exception of the turret and armament, specifications are believed the same as those for the model 2597 (1937) medium tank.
5. HEAVY TANKS. a. Little is known of Japanese heavy tanks. As far as can be ascertained, they have been produced only in limited numbers, and those seen have been reported as being clumsy, lightly armored, and of poor performance. In addition, some years prior to the war, a limited number of "heavies" were bought by Japan. The majority of these (including the "Vickers Independent," weight 32 tons) are obsolete.
b. In 1939, the battle of Nomonhan clearly demonstrated the inadequacy of Japanese tanks. At the conclusion of this conflict considerable reorganization took place within the Japanese Army. It is reasonable to assume, therefore, that Japan is now in possession of a modern heavy tank.
6. AMPHIBIOUS TANKS. a. General. Little specific information is available concerning the Japanese development of this type of tank. Similar to the ground tanks, the first amphibians were purchased from foreign countries, a specific instance being the 3 to 4 ton "Vickers amphibious light tank." Several modifications of this are believed to have been produced by the Japanese.
b. Model 2594 (1934) light amphibious tank. An unconfirmed report indicates the existence of a tank, tentatively identified as the model 2594 (1934) light amphibious tank, possessing the following specifications:
It is considered that the armor and armament, coupled with the dimensions, are hardly compatible with a weight of only 4 tons.
c. New type amphibious tank. The photograph illustrated in figure 250 shows the most modern trend yet encountered in Japanese tank design. No information is available to indicate the model number or date of production. The system of flotation is extremely interesting and is achieved by attachment of a bow and stern pontoon. Pontoons conform to the shape of the hull, and are attached by a series of pincer clamps, which are controlled by a handwheel situated inside the tank, enabling their quick release if so desired. The volume of the bow pontoon is estimated at 220 cubic feet, and that of the stern pontoon at 105 cubic feet. Two rudders are situated in the stern pontoons and are operated from within the hull. Two propellers are fitted to the rear of the tank. With exception of the suspension, this tank is an entirely new Japanese design, the hull being simplified, reentrant angles eliminated, and welding used throughout. In addition, the round turret is of a new type, characterized by its considerably increased diameter, giving the impression of greatly reduced height. To prevent water entering, rubber seals are fitted around all openings up to and including the turret ring. The tank hull is not divided into individual compartments. Suspension closely resembles that of the M 2594 and M 2597 tankettes, excepting that the compression springs are mounted within the vehicle. No specific details are available, but there are definite indications that the primary armament of this vehicle shows improvement. Of particular significance is the coaxial mounting of the turret machine gun. As no Japanese tank has been encountered in the past with its weapons so mounted, this fact must be regarded as a radical departure in their tank design. The following data have been obtained from a preliminary examination:
7. ARMORED CARS. a. Armored car model 25 (?) "Vickers Crossley." This armored car (fig. 251) may be classified as obsolete and is readily identified by its hemispherical turret. A small domed cupola, in two hinged halves, surmounts the turret. Traverse 360°, the turret mounts only two machine guns, although there is provision for four. Each of the weapon openings is covered with a small flap, which is closed when the gun is removed. All machine guns are of the Vickers type. Guns are ball mounted and have a limited traverse independent of that of the turret. The front wheels are single, while the rear wheels are dual. The chassis is believed to be a standard commercial type weighing 2.8 tons. In the past, this armored car was incorrectly classified as the "OSAKA" model 2592 (1932).
b. Armored car model 92 (1932) naval type. This probably was produced in 1932. The insignia indicates that it (fig. 252) is a naval vehicle. In addition to the machine gun in the front and rear, one is mounted on each side of the hull. One is also mounted in the turret. Semielliptic springs provide the suspension for the 6-disc wheel chassis. Wheels are fitted with pneumatic tires. To prevent bellying, when crossing rough terrain, auxiliary wheels are mounted on the frame to the rear of the front wheels. The radiator is provided with armored shutters. Reconnaissance and guard duties constitute the chief role for this vehicle.
c. Armored car model 92 (1932) "OSAKA." Until recently, considerable confusion has existed between this armored car and the model 25(?) "Vickers Crossley," specifications of the "Osaka" being attributed to the latter vehicle. While no details are available, it is believed that the "Osaka" is of Japanese origin, a standard commercial chassis being used for its manufacture. Wheels are fitted with pneumatic tires, the front single and the rear dual mounted. Machine guns are of the Vickers type; one is mounted in the front of the turret. As an extensive free traverse has been allowed to this gun, it is considered possible that the turret is fixed and cannot be traversed. As the design of the driver's front plate gives no indication that the second machine gun is mounted in the front of the hull, it is probable that this weapon is mounted at the rear of the vehicle.
d. Armored car model 93 (1933) "Sumida". This vehicle (fig. 253) has been used extensively in China and was specially designed to run either on railway lines or hard roads. To effect the change from rails to road, the vehicle is raised up by 4 built-in jacks. Solid rubber tires then are placed over the 6 flanged steel wheels, and the vehicle can be driven off the rails onto the road. This operation is said to take 10 minutes. When traveling on rails, 3 solid rubber tires are attached on each side of the hull.
8. ARMAMENT OF JAPANESE ARMORED UNITS. The following weapons are known to be used in Japanese tanks and armored cars:
a. Model 91 (1931) 6.5-mm MG. This weapon (fig. 254) is merely the infantry machine gun, model 11 (1922) adapted to tank requirements by the removal of the bipod. It is considered possible that it has now been replaced largely by the better designed and heavier calibered model 97 (1937) 7.7mm machine gun. For detailed characteristics of the model 11, see chap. 9, sec. II.
b. Model 97 (1937) 7.7-mm MG. This is the standard MG (fig. 255) at present used in Japanese tanks. A shoulder controlled weapon, it is fitted with conventional sights. It may readily be identified by the specially designed modified stock. When used for tank purposes, a fixed focus telescopic sight of 1 1/2 power x 30° field of view is usually fitted. To prevent injury to the gunner, a heavy rubber eye pad is attached to the rear of the telescope. By the addition of a bipod, this weapon may be converted to ground purposes.
c. Model 94 (1934) 37-mm tank gun. Although bearing the same type number as the field piece of similar caliber, these two weapons must in no way be confused, for each has been designed for its own specific purpose. In addition, ammunition is NOT interchangeable, as the chamber of the tank gun (fig. 256) is considerably smaller than that of the antitank gun. This gun appears to constitute the primary armament of Japanese light tanks. In addition, there is evidence that one model of tankette is similarly equipped. It is considered that this weapon has neither the performance nor armor piercing qualities of the U.S. 37-mm tank gun. Mounted in the turret, the Japanese weapon is carried by two sets of trunnions, one set allowing the gun a limited "free" traverse, while the other permits the gun to be elevated or depressed. Traverse and elevation/depression are manually applied by means of an adjustable shoulder rest attached to the left side of the cradle. The main traverse is obtained by rotating the turret. Telescopic sight, pistol type grip, and trigger are mounted to the left of the gun.
d. Model 1 (1941) 37-mm tank gun. This gun has been recovered, but detailed examination has not yet been made. However, from the length of the barrel and the size of the chamber, a muzzle velocity much higher than that of Model 94 (1934) 37-mm tank gun may be expected, and it is believed that this gun will have good armor-piercing qualities.
e. Model 97 (1937) 57-mm tank gun. It is believed that this weapon (fig. 257) is the standard heavy armament of Japanese medium tanks. The gun is mounted in the turret and is manually controlled. Elevation and depression are free. The weapon may be traversed also approximately 10 degrees to left and right, independently of the turret. Although several specimens have been captured, the condition of the guns has prevented a detailed examination. Sufficient information is available, however, to indicate that it is a short barrelled, medium velocity weapon that would be more suitable for employment against ground troops. This would appear to conform to the Japanese past policy of using mainly tanks for the close support of infantry, rather than for tank vs. tank action. No information is available to indicate if this policy is still being adhered to, or whether the future trend will be to substitute a high velocity weapon similar to the model 1 (1941) 47-mm antitank gun (for characteristics see ch. 9, sec. II).
f. Model 90 (1930) 57-mm tank gun. No information is available concerning this weapon. Photographs of early Japanese tanks suggest that this gun is a short barrelled piece resembling the model 97. It is probable that the model 90 was the forerunner of the latter weapon.
g. 47-mm tank gun. While no details are available, indications are that the Japanese are now mounting a 47-mm gun in certain of their medium tanks. It is also reported that a model of the light tank is mounting a weapon of this caliber. It is reasonable to assume that this gun is a modern, high velocity antitank piece, in all probability, a modified form of the model 1 (1941) gun adapted to tank purposes. For characteristics of the model 1 (1941) 47-mm antitank gun, see section II, chapter 9.
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