Japanese Army fighter aircraft of the Second World War

Japanese Army fighter aircraft of the Second World War
The Imperial Japanese Army and Navy had separate and rival air forces with their own aircraft: separate bombers, fighters, transports, and reconnaissance. Rivalry between the two arms was intense, preventing them from sharing resources, research data and even spare parts. In some regards, the Army air forces had better aircraft than the Navy especially from mid-war onwards.

On the other hand it might be said that the Army was using too many types of fighters, limiting large scale production.

Army Fighters
Nakajima Ki-27 ?/Nate/Abdul

The Imperial Japanese Army Air Forces’ (IJAAF) first monoplane fighter introduced in 1936. Lightweight construction, non-retractable landing gear, highly manoeuvrable and performed well against Soviet Polikarpov I-16 Ishak/Rata at the Battle of Nomonhan and over China.

The Army had held a competition for aircraft manufacturers to select a suitable fighter. Mitsubishi offered a modified Navy fighter that beat everyone else, but the Army was offended and refused to use a Navy design. The Ki-27 was designed to beat Mitsubishi’s Navy prototype (which later served the Navy as the A5M Claude).

The Nate was still in use at the beginning of the Second World War, although Nakajima had ceased production and the Army was bringing its successor to the front, the Ki-43 Hayabusa.

Nakajima Ki-43 Hayabusa/Oscar

Another highly manoeuvrable fighter in the IJAAF, and successor to the Ki-27. It was introduced in 1941, but even as the war began, some units were still flying the Nate. Although Nakajima and other manufacturers believed that power and speed with heavy armaments were the future, the Army insisted on lightweight, highly manoeuvrable fighters. Development was delayed by the Army’s insistence on high manoeuvrability at least matching the slower Ki-27. Eventually the introduction of combat flaps made it more manoeuvrable than the Zero.

It was mainly let down by weak armaments: two 7.7mm machine guns mounted above the cowl. The three support spars in the wings were too closely spaced to mount any weapon in the wings. Later the weapons were upgraded to two 12.7mm machine guns firing explosive rounds, but the rounds often exploded prematurely on the surface of target aircraft instead of piercing the skin and exploding within, doing terrible cosmetic damage rather than destroying the target.

It was also fragile and could not withstand much damage. Later versions backed the pilot seat with armour to reduce pilot deaths and also protected the fuel tanks, so that the fighter would break up instead of exploding, giving the pilot time to bail out.

Its manoeuvrability was phenomenal. Allied pilots reported seeing pilots perform double-double Immelmanns, horizontal spins, flip rolls, snaking vertical climbs, and extremely tight turns that would cause even a Zero to stall and crash. An Immelmann is a vertical half loop with the plane ending up flying in the opposite direction. Most aircraft including the Zero would be hard put to perform one, and these aircraft were doing four in succession!

Kawasaki Ki-61 Hien/Tony

Japan’s only fighter that uses a water-cooled engine instead of air-cooled radials. The Hien was introduced in 1943 and was mistaken for an Italian import, thus the Allied codename “Tony”.

While a sizeable number of pilots wanted lightweight highly manoeuvrable fighters, the Japanese Army hedged its bets based on the expert opinions of the manufacturers and commissioned several “speed fighters”, well armed, fast, and giving more protection to the pilots.

Kawasaki’s Hien de-emphasized manoeuvrability in favour of speed, although it still was a very good at turning by Allied standards. At introduction, it was the fastest fighter in the Japanese stable, and faster than most American planes in the Pacific. It had better armament than its contemporary Ki-43, with two cowl machine guns and two cannons.

Most Allied pilots had learned they could escape Japanese aircraft by a shallow power dive, outrunning them, but the Hien nullified this tactic because it too was a good power diver. It could outturn the faster American planes, and outrun the slower ones.

Its engine was a modified version of the engine powering the German Messerschmitt Bf-109E but shaving 40 pounds of metal to make it lighter, but this made the already complex engine very hard to build, with a high rejection rate. Japanese manufacturers found it difficult to match German precision in metal casting. It was also difficult to maintain in the jungle bases of the Pacific, and broke down often in the tropical heat.

While an excellent design, its unreliable engine prevented the fighter from achieving its potential. Engine problems frequently grounded the aircraft, and pilots often did not dare push the engine to maximum power. Sometimes they did and the engine would not deliver.

Its engine problems were solved in the Ki-100.

Unlike most Japanese fighters, the Hien/Tony was very sturdily built and could survive more damage. Not only were the fuel tanks protected and the cockpit armoured, the fuselage itself was very strong. In the final stages of the war, fighter pilots sometimes tried to destroy B-29 bombers by colliding with them. Most other aircraft used disintegrated killing their pilots, but Hien pilots would survive and parachuted safely to do it again!

Nakajima Ki-44 Shoki/Tojo


Introduced in late 1941, the Ki-44 Shoki was intended to be a bomber interceptor. As such, the design de-emphasized manoeuvrability in favour of speed and climb. Nakajima mounted the largest and most powerful engine they had on a small fuselage. It was also more heavily armed than the Ki-43, either carrying four 12.7mm machine guns, or two cowl machine guns and two wing cannons of 20mm caliber.

Most units were pulled back to Japan after the Doolittle Raid with some remaining in Sumatra. They saw action and were fearsome aircraft over Sumatra late in the War, although were less successful against B-29 attacks over Japan due to poor engine performance at high altitudes.

In the later stages of the war, Allied aircraft designers tended to favour power and speed over manoeuvrability for fighters. Having these very traits, interceptors such as the Shoki were found to be competitive with middle and late war Allied fighters, and found itself in fighter vs fighter combat as often as bomber interception.

Kawasaki Ki-45 Toryu/Nick

A twin-engined heavy fighter, intended as long range bomber escort, it was unable to outperform enemy single-engined fighters. Like its German counterparts (Me-110 and Ju-88) it was repurposed as a night fighter where it was reasonably successful, even though Japanese pilots relied on night vision instead of on-board radar as the Germans did. Japanese night fighter pilots were selected from among pilots with excellent night vision.

Like the German night fighters, the Toryu was fitted with fixed upward-firing cannons on the roof, to shoot up at the bellies of bombers. The Germans called it Schrag Musik (Jazz Music), but the Japanese had come up with the same idea on their own. The undersides of bombers were seldom equipped with defensive guns since most of the belly space was occupied by the bomb load, and this defensive blind spot was exploited by the Jazz Music guns.

In 1945 the Toryu (“Dragon Slayer”) found itself having to live up to its name, slaying B-29 superbombers that were incinerating Japanese cities with incendiaries.
Nakajima Ki-84 Hayate/Frank

This purpose-built fighter is widely acknowledged to be Japan’s finest, or at least the finest built in large numbers. Clean lines, powerful 2000 hp Homare engine, sturdily built (although not quite as solid as the Hien/Tony), and well-armed. It could do anything the new US fighters could do, climb and dive with them, pounce from above, give chase if they run, and with the combat flaps deployed, outturn the faster planes.

It was mostly let down by the unreliable Homare engine, rated at 2000 hp on paper but delivering 1500-1800 hp in practice, although it was more reliable than the inline powering the Ki-61. There were also problems with its landing gear, which was sometimes not properly heat-treated and could snap off on a rough landing. But overall, a fighter to be reckoned with.

Kawasaki Ki-100 Goshikisen/Tony

This is the Ki-61 Hien/Tony unleashed. While an excellent aerodynamically clean design, the original Hien had suffered from teething problems with its complex engine, which meant that pilots seldom pushed the fighter to maximum power.

That was to change in 1945. A US bombing raid destroyed Kawasaki’s engine factory, leaving hundreds of completed Hien airframes without engines. In dire straits, the Japanese high command ordered Kawasaki to experiment with fitting the aircraft with the Mitsubishi Kinsei radial engine. The results astounded everyone.

The engine was 300 pounds lighter, since it did not require an engine block to contain liquid coolant, nor pipes for them or radiator. Pilots now had 1500 hp to play with, and were no longer afraid to push the engine to full power. It was now possible to use boost, overpressuring the cylinders to momentarily give bursts of extra 300 hp.

Pilots tested the Ki-100 against the Ki-84 Hayate, and concluded that this fighter was better. This fighter is the Hien/Tony as it was meant to fly: a well-armed speed fighter on par with the Hayate.

However, coming as it did at very near the end of the war, meant that only a few hundred were built, with the first 200 or so being conversions.

(Japanese Navy Fighters to follow)


One thought on “Japanese Army fighter aircraft of the Second World War

  1. The Nate was in such strong numbers vs the Navy’s Claude. It saw more combat after Pearl Harbor until the Ki 43 took over. The Zero started with 400 vs 40 Ki 43s, so the Claude was replaced much sooner.
    If only the Ki 43 could have 4 guns like theZero.
    The Army didn’t suffer the loss of so many veteran pilots like the Navy did at Midway, so when Nakajima kept up with the Americans with the Ki 44 and Ki 84, the Ki 43 remained their favorite….in production for the duration.

    They should have at least added a cannon or two around the Oscar’s cowl, mid-war.

    When the Ki 61 stumbled with engine issues in the tropics, the reliable Ki 44 should have picked up the slack in New Guinea …etc. It deserved more production. How many Tony flights with losses of 2/3 their number non-combat, do you need to make a change?

    The other new fighters were also unreliable like the Ki 61, Army and Navy. So the competant Ki 44 in mass quantities would have been timely. True, it had short legs but with drop tanks the Tojo was ok. I like the bomber killer Ki 44-IIc with 4 Ho-3 high velocity 20mm cannons. Slow RoF but the heaviest 20mm shell in the war! They were a match for the B-29.

    Of course, had the Kawasaki team not been so stubborn for the inline motor, and contemplated a mid-war Ki 100, that would have been a reliable world-beater in the right time-frame. Meantime the Ki 84, J2M, and N1K engines could have matured. As it was, the hoped for Ki 61-II proved worse than the first Tony in reliability.
    Can you imagine say, 3,000 – 5,000 Ki 100s!
    Just a tenth that number made quite an impression in 1945!

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