Range bought with fire

What makes it special

Full specifications

Baseline note: the figures below describe the Mitsubishi G4M1 Model 11 (Navy Type 1 Land-based Attack Aircraft Model 11, Allied reporting name “Betty”), the mark that helped sink Force Z, carried Admiral Yamamoto to his death and was destroyed in hundreds over the Solomons. Deltas for the G4M2 of 1943, the G4M2a and the belatedly protected G4M3 of late 1944 are given in grey. Note that the English Wikipedia specification panel for the G4M1 omits a service ceiling entirely and quotes a 5,040 km ferry range, where Francillon’s tables give 8,500 m and a maximum range of 6,033 km; both readings are reproduced below rather than quietly reconciled.

Armament & payload

The G4M carried one torpedo further than any other aircraft in the world could, and it did so by leaving out everything that would have kept its crew alive

The Imperial Japanese Navy’s land-based attack aircraft — the rikko — existed to do a job no other navy asked an aeroplane to do: find an enemy battle fleet hundreds of miles out in open ocean and torpedo it, from an airfield, without a carrier. The G3M had proved the idea worked. In 1937, two months after the G3M entered combat over China, the Navy asked Mitsubishi for its successor, and the 12-Shi requirement was brutal: 398 km/h, a cruising altitude of 3,000 m, 3,700 km carrying an 800 kg torpedo or bomb load and 4,722 km empty. Kiro Honjo’s team met all of it. They met it by treating the wing as one enormous integral fuel tank and by declining to line it, armour it or purge it.

This was not an oversight and it was not ignorance. It was an explicit exchange, made with the arithmetic in front of everyone: self-sealing liners and armour would have cost several hundred kilograms, and several hundred kilograms would have cost the range that the entire doctrine rested on. The Navy took the range. What it bought with it, in the first six months, was extraordinary — a bomber that could strike from Formosa to the Philippines, from Indochina to the Gulf of Siam, from Rabaul to Guadalcanal, and hit ships at the end of the flight. What it bought after that was the systematic destruction of the Navy’s trained aircrew. Allied pilots called it the one-shot lighter, the flying Zippo and the flying cigar, and the names were not exaggeration: a single burst of .50 calibre into the wing root routinely produced a fire that could not be put out.

On 10 December 1941 the bargain paid in full. The 22nd Air Flotilla put 85 strike aircraft and three scouts against Force Z off Malaya, and most of them were G3M Nells — but the twenty-six torpedo aircraft of the Kanoya Kokutai, flying from Thu Dau Mot in southern French Indochina, were G4M1s, and they did the killing. A single Genzan Nell had already crippled Prince of Wales with one torpedo aft. At about 12:20 the Kanoya Bettys arrived, split, and attacked both ships at once: three torpedoes into Prince of Wales’s starboard side — at the bow, opposite B turret and abaft Y turret — and a hammer-and-anvil run on Repulse from both bows simultaneously, which no amount of helm could answer. Repulse had already dodged nineteen torpedoes; she took at least four in a few minutes and sank at 12:33. Prince of Wales followed at 13:18. The Kanoya Kokutai lost two aircraft shot down and a third written off on landing. Two capital ships, at sea, under way, destroyed by shore-based aircraft, for the first time in history.

Eight months later the same aeroplane met an enemy with radar, proximity-fused anti-aircraft ammunition and carrier fighters overhead. On 8 August 1942, the second day of the Guadalcanal landings, twenty-three torpedo-armed G4M1s attacked the American transports off Lunga Point. Eighteen were shot down and every one of those eighteen crews — roughly 120 men — was lost. One burning Betty crashed into the transport George F. Elliott, which had to be scuttled, and a torpedo crippled the destroyer Jarvis, sunk the next day with all hands. That was a good day by later standards. Between August and October 1942 more than a hundred G4M1s were lost over the Solomons, and Japan had no reserve of trained rikko crews to replace them. At Rennell Island on 29 and 30 January 1943 the type sank the cruiser Chicago in a night torpedo attack and lost ten of forty-three aircraft doing it, about seventy aircrew including Lieutenant Commander Higai. Japanese and American loss accounts for the Solomons night attacks rarely agree within twenty per cent; the figures here are the Allied ones.

The vulnerability then killed the man who had planned the war. On 18 April 1943 two G4M1s of the 705th Kokutai left Rabaul at 06:00 with six A6Ms of the 204th Kokutai as escort, carrying Admiral Isoroku Yamamoto in aircraft T1-323 and Vice Admiral Matome Ugaki in the second. Sixteen P-38G Lightnings of the 339th Fighter Squadron, sent on the strength of decrypted signals traffic, met them over Bougainville at 09:34 — one minute early. Rex Barber is credited by most modern historians with the burst that set the leading Betty’s wing alight; it went into the jungle north of Buin, and Yamamoto’s body was found the next day, thrown clear, still upright, one gloved hand on his sword. Ugaki’s aircraft was shot into the sea off Moila Point and he survived it. One P-38, Lieutenant Raymond Hine’s, did not come back. The whole engagement lasted a few minutes, and it worked because a Betty that has been hit in the wing does not need to be hit twice.

By 1945 the aeroplane had one last job, and it was the worst one. Stripped of bomb-bay doors and fitted with shackles, the G4M2e carried the Yokosuka MXY7 Ohka — a 2,140 kg rocket-boosted piloted bomb with a 1,200 kg warhead and a release range of about 37 km. Hanging that under a Betty made a slow aircraft slower and a fragile aircraft helpless, and it required the mothership to fly straight and level deep inside a fighter screen. On 21 March 1945 Lieutenant Commander Goro Nonaka led eighteen G4M2e of the 721st Kokutai — the Jinrai Butai, the Divine Thunder Corps — from Kanoya against Task Force 58. Fifteen carried Ohka. Of the fifty-odd Zeros promised as escort only about thirty arrived. Hellcats intercepted them well short of the fleet; every one of the eighteen Bettys was shot down and about 160 men died, the Ohka pilots among them, without a single weapon reaching a ship. Nonaka, who had called the operation Minatogawa after the battle Kusunoki Masashige rode into knowing he would die, was killed with the rest. Ohka would eventually sink exactly one ship, the destroyer Mannert L. Abele, on 12 April 1945.

Sourcing caveat: dimensions, weights and performance follow Francillon’s tables in Japanese Aircraft of the Pacific War as reproduced by the standard references; gun fits varied between production blocks and field modification was constant, so photographs frequently disagree with the official schedules. Torpedo figures are for the Type 91 Kai-3 as issued in 1943. Loss figures for Japanese units are Allied assessments where Japanese records do not survive.

Variants

Mitsubishi built 2,435 G4Ms and spent five years trying to give the aeroplane back what the first specification had taken out of it

The G4M’s development history is the history of one mistake being slowly and incompletely corrected. Span never changed; wing area never changed; the internal bay never grew. What changed was engines, guns and, at the very end, the wing structure itself. Every improvement added weight, every addition of weight ate range, and the one improvement that actually mattered — protected fuel — was left until the G4M3 of October 1944, of which 91 were built out of 2,435.

It is worth being precise about why. Rubber ply sheeting was applied to G4M1 tanks from March 1943 and carbon-dioxide extinguishers were fitted, but the wet-wing structure meant there was no cell to line properly; the sheeting slowed a leak, not a fire. The G4M2 of 1943 added a powered turret, a laminar-flow wing and 270 more horsepower a side, and the article that describes it in the reference literature says flatly that the redesign failed to rectify the type’s vulnerability. Only the G4M3, with a new wing built around separate self-sealing cells, crew armour and a redesigned tail position, was a survivable aeroplane, and by October 1944 there was neither the fuel, the aircrew nor the strategic situation to make use of it.

Alongside the bombers ran a second, stranger line. The G6M1 of 1940 was an attempt to make the airframe escort itself: a ventral gondola with two 20 mm cannon, more guns elsewhere, no bomb load. It was heavier than a loaded G4M and could not keep formation with unloaded G3Ms, which is a complete refutation of the concept in one sentence. All thirty were converted to crew trainers and then to twenty-seat transports, and it was almost certainly a machine of that family — a Type 1 land-based transport — that led the surrender delegation to Ie Shima in August 1945.

G4M1 Model 11 (1941–January 1944 / 1,172 including prototypes)

Kasei 11 of 1,530 hp, later Kasei 15 from March 1942; one 20 mm tail gun and four 7.7 mm hand-held guns; doorless bomb bay; no protection as built. Propeller spinners from summer 1942, rubber ply tank sheeting from the 663rd airframe in March 1943, tail-gunner armour and a redesigned tail cone from August 1943, individual exhaust stacks from September 1943. The mark that fought and lost the Solomons.

G6M1 (1940 / 30)

Long-range escort fighter conversion with a ventral gondola mounting two 20 mm Type 99 cannon and no bomb load. Too heavy to escort anything; never used in the role. The Navy’s insistence on this idea is part of why the bomber went into production without protection.

G6M1-K and G6M1-L2 (1941–42 / conversions of the 30 G6M1)

The escorts rebuilt first as aircrew trainers and then as Type 1 land-based transports carrying up to twenty passengers — the version that spent the rest of the war moving staff officers, and that appears in the surrender flights of August 1945.

G4M2 Model 22, 22 Ko, 22 Otsu (prototype December 1942, service mid-1943 / 429)

Kasei 21 of 1,800 hp with four-blade feathering propellers, LB laminar-flow wing, wider tailplane, more fuel, and an electrically powered dorsal turret with a 20 mm Type 99. Ko added H-6 radar and 20 mm waist guns; Otsu fitted the longer Type 99 Model 2. Faster, better armed, better at altitude — and still a wet wing.

G4M2a Model 24, 24 Ko, 24 Otsu, 24 Hei (1944 / 713)

Kasei 25 of 1,800 hp, recognisable by the carburettor intake on top of the cowling, with bulged bomb-bay doors for a larger load. Hei added a 13.2 mm Type 2 gun in the nose tip and moved the radar aerial above the nose cone. Numerically the most-built Betty after the G4M1.

G4M2b Model 25, G4M2c Model 26, G4M2d Model 27 (1944 / one, two and one aircraft)

Engine testbeds: the Kasei 25 Otsu, the turbocharged Kasei 25b Ru and the Kasei 27 respectively. Four aircraft in total, none in service; the turbocharged Model 26 in particular came far too late to give the type the high-altitude performance it needed against B-29 escorts.

G4M2e Model 24 Tei (late 1944–1945 / conversions of Model 24 Otsu and Hei)

Ohka carrier: bomb-bay doors removed, belly shackles for a 2,140 kg MXY7, added armour for the pilots and the fuselage tanks. Flown by the 721st Kokutai. On its first operation, 21 March 1945, all eighteen aircraft committed were shot down.

G4M3 Model 34, 34 Ko, 34 Otsu, 34 Hei (October 1944–1945 / 91)

The aeroplane the G4M should have been in 1941: redesigned wing with separate self-sealing tanks, proper crew armour, dihedral on the tailplane, and a new tail gunner’s compartment modelled on late B-26 practice. Kasei 25 engines, 470 km/h, and 91 built. Three and a half per cent of total production, arriving in the last ten months of the war.

G4M3 Model 36 (1945 / two prototypes)

Turbocharged Kasei 25b Ru engines in the G4M3 airframe. Two aircraft, no production, no operational use.

No licence production, no export (1941–45)

Every G4M was built by Mitsubishi for the Imperial Japanese Navy, which operated the type in 37 kokutai. There were no exports and no second source. The only other operators were captors: the USAAF and the RAF flew evaluation aircraft, and the Republic of China Air Force took over at least one G4M2 seized at Tainan.

Closing caveat on survivors: of 2,435 built, exactly one substantially complete G4M exists. G4M1 Model 11 serial 1280, built on 16 April 1942 and recovered from Babo airfield in Indonesia in 1991, is displayed unrestored in a diorama at the Planes of Fame Air Museum, Chino, California; it is the only complete airframe anywhere and it has never been restored. Everything else is fragments. The Smithsonian holds the forward fuselage of a G4M3 Model 34; the Kawaguchiko Motor Museum in Yamanashi displays a restored G4M2 fuselage; two G4M1s, serials 1800 (701st Kokutai) and 2806, were recovered from Ballale in the Solomon Islands in August 2018 as wrecks. Admiral Yamamoto’s aircraft, G4M1 serial 2656 with tail code 323, still lies in the jungle near Panguna on Bougainville where it fell on 18 April 1943, and remains the most visited piece of Japanese aircraft wreckage in the Pacific. No G4M flies, and none ever will. Note also that accounts of the August 1945 surrender flights differ: Japanese sources describe two aircraft leaving Kisarazu on 19 August — a Type 1 land-based transport as Bataan 1 and a Type 1 land attack aircraft as Bataan 2, both painted overall white with green crosses — while at least one English-language source states that four white G4M1s reached Ie Shima. Two is the better-attested figure. On the return leg one aircraft collapsed its undercarriage taxiing at Ie Shima and the other ran out of fuel and force-landed on the beach at Sameshima near the mouth of the Tenryu river on the night of 20 August; the delegates waded ashore with the surrender documents intact and reached Tokyo the following day.

From long-range striker to surrender transport

From the war: twelve Betty stories

The Betty in pictures

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The Betty in motion

Video coming soon — we are sourcing a high-authority archival film of the G4M “Betty” for this exhibit.

Where the Betty flew

The score that defines it

The Betty’s combat record is a story of spectacular early success and a mounting bill for its lack of protection. Its greatest day came in the war’s first week; thereafter the same design that gave it reach made it fatally easy to burn. It served only with the Imperial Japanese Navy, from the opening of the Pacific war to the surrender.

Compare the combat record of every military aircraft. Figures as of July 2026.

Everything people ask about the G4M Betty

Continue the tour

Every fact, checked

• HistoryNet — Mitsubishi G4M: Why Betty BombedDesign bargain, Kiro Honjo, the flammability problem and crew nicknames.
• Smithsonian National Air and Space MuseumReference for the surviving G4M3 forward-fuselage section and variant data.
• The National WWII MuseumOperation Vengeance and the April 1943 shoot-down of Yamamoto’s G4M.
• Air & Space Forces MagazineThe P-38 interception that killed Admiral Yamamoto.
• Royal Air Force MuseumThe Yokosuka MXY-7 Ohka piloted rocket bomb carried by the G4M2e.
• Pacific WrecksThe white, green-crossed surrender-delegation Bettys (“Bataan”), 1945.
• History of WarSpecifications, range figures and variant history for the G4M.
• Naval History and Heritage CommandThe 10 December 1941 loss of HMS Prince of Wales and HMS Repulse.