Type 3 Chi-Nu

By the end of 1942 the Imperial Japanese Army knew exactly what was wrong with its tanks, because it had met the answer. The M4 Sherman was in the Pacific, and the standard Japanese medium — the Type 97 Chi-Ha — carried a 47 mm gun that defeated about 40 mm of plate at 500 m and 30 mm at a thousand. A Sherman’s glacis presents roughly 90 mm of steel along the path of a shot. The gap was not marginal and no amount of tactics closed it.

What Japan needed was a bigger gun, and it had one — not in a tank, but in the field artillery. The Type 90 75 mm field gun was tested against captured American armour and found able to penetrate an M4 at 500 m. The decision that followed is the whole origin of this tank: take the field gun, adapt it, and build a turret that would hold it.

The result was the Type 3 75 mm tank gun, an L/38 weapon firing at 680 m/s, and a new turret to carry it. The hull was the one Japan already had in production: the Chi-Ha’s, unchanged in its essentials, with the proven Mitsubishi Type 100 V-12 diesel of 240 hp driving 19 tonnes to 39 km/h.

The turret was the genuinely new part — a large hexagonal structure of welded plate, at a time when much Japanese armour was still riveted, roomy enough for a commander, gunner and loader to work the 75 mm properly. Japan was doing in 1943 what Italy did with the Semovente and Germany with the Marder in the same period: solving an anti-tank problem by moving an existing artillery piece onto an existing chassis.

The Type 3 defeated 90 mm of armour at 100 m and 65 mm at 1,000 m. Set against the tank it was designed to fight, those numbers need reading carefully rather than celebrating. A late Sherman’s glacis is 64 mm set at 47°, about 94 mm of line-of-sight plate; an early one is 51 mm at 56°, about 91 mm. At a kilometre the Chi-Nu’s 65 mm does not get through either. At a hundred metres its 90 mm is level with them, which in practice means sometimes.

But the glacis is not the only way into a Sherman. The turret front is 76 mm and the hull sides are 38 mm, and both are comfortably within reach of the Type 3 at ordinary combat ranges. Through the turret, through the flank, or from close range, this was the first Japanese tank weapon that could reliably destroy an M4.

Nothing comparable happened to the protection. The Chi-Nu carried 50 mm on the hull front and 50 mm on the turret face, with 35 mm on the turret cheeks, 20 to 25 mm on the sides and 20 mm at the rear. The roof was 10 mm on the turret and 12 mm on the hull.

Those are 1941 figures on a 1944 tank. A Sherman’s 75 mm gun defeated about 60 mm at 914 m and 66 mm at 457 m, which means the Chi-Nu’s thickest plate was penetrable at any range at which the two could see one another. Japan had built a tank that could kill a Sherman and could not survive one, and it had done so knowingly: the weight had to go somewhere, and it went into the gun.

Production ran from 1944 into 1945, and the totals given are between 144 and 166 — Mitsubishi delivered 55 in 1944 and the rest in the months that followed, in a country whose industry was being systematically burned out by B-29s. For comparison, the United States built roughly 49,000 Shermans.

The tanks were issued. At least six tank regiments on Kyūshū and Honshū received them, including the 4th Tank Division at Fukuoka and the 1st Armored Division around Tokyo. And there they sat: kept for training and largely immobile, because by 1945 there was not enough petrol in Japan to drive them.

The Chi-Nu existed for one operation, and that operation was defensive. Ketsu-Go was the plan for the defence of the Home Islands against the Allied landings everyone knew were coming — Kyūshū first, then the Kantō plain. Every Chi-Nu built was held back for it. None was shipped to the Philippines, to Okinawa or to any of the island garrisons that were being destroyed one by one while these tanks stood in their depots.

The invasion never came. Japan surrendered in August 1945, and the 4th Tank Division was demobilised the following month without the division having fought. The Type 3 Chi-Nu did not see combat at any point in the war.

It is easy to file the Chi-Nu with the other late-war machines that arrived too late to matter, and easy in the wrong way. This was not a prototype and not a paper project: it was a production tank, built in three figures, issued to divisions, standing ready in the country it was meant to defend. What defeated it was not the drawing office but the two years between recognising the problem in 1942 and having the answer in service in 1944 — and then the absence of the fuel to move the answer.

The measure of it is this. The gun that finally made a Japanese tank dangerous to a Sherman came from a field gun designed in 1930, and Japan had held that gun in its own artillery parks the whole time.

• Steven J. Zaloga, Japanese Tanks 1939–45 (Osprey, New Vanguard, 2007).
• Andrzej Tomczyk, Japanese Armor (AJ Press).
• Leland Ness, Rikugun: Guide to Japanese Ground Forces 1937–1945 (Helion).
• US War Department, Handbook on Japanese Military Forces (TM-E 30-480, 1944).