Second World War
The Mitsubishi G3M Type 96 Attack Bomber 'Nell' was the Japanese Navy’s main land based torpedo and high level bomber in the years before the start of the Pacific War. Although it was in the process of being replaced by the G4M ‘Betty’ at the end of 1941 the 'Nell' still played a major part in the early Japanese conquests in Malaya and the Pacific. Its most successful moment came on 10 December 1941, when sixty G3M2s took part in the attack that sank the British warships HMS Prince of Wales and HMS Repulse, shattering British naval power in the far east.
Work on the aircraft that would evolve into the G3M began in 1933. Early that year the prototype of the Hiro G2H1 Type 95 heavy attack bomber made its maiden flight, but despite its impressive range it was clear that this aircraft was too slow and too cumbersome to fill its planned role. Rear Admiral Isoroku Yamamoto, who in 1933 was in charge of technical development at Naval Aircraft Establishment wanted an all-metal long range land based bomber. This was to be used as a defensive weapon, attacking any hostile fleet approaching Japan from bases on the islands of the Japanese Pacific Empire.
In the spring of 1933 Mitsubishi were given a contract to produce a twin engined land based long range aircraft, officially as the 8-Shi special reconnaissance plane, but actually as a prototype for the bomber. The resulting aircraft, developed by Mitsubishi as the Ka.9, and later given the Naval designation G1M1, was a great success. It had a slender streamlined fuselage, and used Junkers-style double wings (a second small wing was attached to the rear of the main wing, and the small gap between the two wings improved lift).
The Ka.9 made its maiden flight in April 1934. Admiral Yamamoto soon made his own successful test flight, and Mitsubishi were given a contract to develop the Ka.9 into a bomber, with the new designation of Navy Experimental 9-Shi attack bomber. This time Mitsubishi were given military specifications which they had to match – the new aircraft had to be able to carry a 1,764lb torpedo, and was to be armed with three 7.7mm machine guns.
The new aircraft was given the Mitsubishi designation Ka.15. The design team lead by Sueo Honjo produced an aircraft that combined the wings of the Ka.9 with a wider fuselage, which had enough space to carry three retractable gun turrets. The typical Junkers corrugated surfaces at the rear of the Ka.9 were replaced with smooth panels, which reduced drag. The twin vertical control surfaces and rudders of the Ka.9 were replaced with a larger version, to compensate for the increase in weight. As originally designed the Ka.15 could carry a single torpedo underneath the fuselage, and so no provision was made for an internal bomb bay. The first prototype made its maiden flight in July 1935, and in the following year the Ka.15 was put into production as the G3M1 Navy Type 96 Attack Bomber Model 11.
The G3M benefited from an extensive development programme, which saw the construction of twenty one prototypes and preproduction aircraft. The first six aircraft were produced as sold nosed torpedo bombers, with a bomb aiming window below the pilot’s cockpit. The remaining fifteen aircraft were modified to serve as prototypes for a high level bomber, with a glazed bombardier’s nose, a navigator’s astrodome and external bomb racks capable of carrying 1,764lb of bombs. Aircraft No.8 was also given increased dihedral on the main wings.
Three different engines were used on the prototypes. The 1st, 2nd, 5th and 6th were given 750hp Hiro Type 91 liquid-cooled engines driving fixed-pitch wooden propellers. The 4th (solid nosed) and 11th (glazed nosed) aircraft were given two 910hp Mitsubishi Kinsei 3 fourteen-cylinder air-cooled radial engines and variable-pitch three-blade Hamilton Standard metal propellers. The remaining aircraft all received 830hp Mitsubishi Kinsei 2 radial engines and fixed-pitch wooden propellers.
It soon became apparent that the solid nosed version could act as both a torpedo and high level bomber, and so it entered production as the G3M1 Model 11, powered by the Kensei 3 engine. The production aircraft had a larger cockpit and modified canopy, and were armed with three 7.7mm machine guns. Only 34 G3M1 Model 11s were built before production moved onto the G3M2.
The G3M2 was the main production version of the ‘Nell’. It was produced in two versions – the Model 21 which was given more powerful engines, and the Model 22 which saw the defensive armament increased by the addition of a large “turtle back” turret carrying a 20mm cannon. The G3M2 was produced by Mitsubishi and by Nakajima.
The final production version of the ‘Nell’ was the G3M3 Model 23, produced from 1941 by Nakajima. This was externally identical to the G3M2 Model 22, but was powered by two Kensei 51 engines, raising the top speed by 26mph to 258mph. Extra fuel was also carried, increasing maximum range to an impressive 3,871 miles.
The G3M’s combat debut came on 14 August 1937, during the Sino-Japanese War. The Japanese Navy decided to attack Shanghai in an attempt to end the war quickly. Japanese troops began to land at Shanghai on 11 August, and three days later G3Ms from the Kanoya Kokutai (Naval Air Corps) launched the first ever trans-oceanic bombing raid, attacking Shanghai from their bases on Taipei (Formosa). There the unescorted bombers ran into unexpectedly strong Chinese fighter opposition, masterminded by General Claire Lee Chennault. Six of the eighteen G3Ms that attacked the flight training school at Hangchow were shot down. On the following day 24 G3Ms from the Kisarazu Kokutai, operating from Omura on Kyushu made a 1,150 mile round trip to attack Shanghai and Nanking, once again suffering heavy losses.
The long range bombing programme had to be halted until the Mitsubishi A5M1 ‘Claude’ fighter entered service in September 1937. By then the G3M units had moved to bases in China, and once the Japanese fighters had swept the older Chinese types out of the skies the bombing raids resumed. By the end of the year the Chinese capital of Nanking had fallen, but any prospect of a short war soon ended. During 1938 the G3Ms once again had to operate without fighter escort, this time coming up against Soviet fighters operating in support of the Chinese government. Once again the G3Ms suffered heavy losses, but these Japanese setbacks were overshadowed by the bombing of civilian targets further south.
The attention of the international community focused on the bombing of Canton on 28 May 1938, when 600 civilians were killed by bombs dropped from G3Ms. A regular bombing campaign followed, and in June 1938 both Britain and the United States condemned the bombing of Chinese civilians.
By the end of October the Japanese had captured both Canton and the new Chinese capital at Hankow, but once again the war continued. Chiang Kai-shek moved to Chungking, forcing the Japanese to continue using the G3M on unescorted raids. In the summer of 1940 the G3M units reached their peak, with 130 aircraft on charge. The bombing campaign continued unhindered throughout 1941, and only came to an end towards the end of the year when the Japanese Navy pulled most of its G3M and G4M units out of China in preparation for the wider war that was about to start.
Second World War
In December 1941 the Japanese Navy had 204 G3M2s and G3M3s in front line units, and 54 in second line units. On the first day of the Pacific War (8 December west of the International Date Line) fifty three G3M2 bombers attacked Clark Field and other air bases on the Philippines from bases in Southern Formosa. Thirty six G3M2s attacked Wake Island from Kwajalein, destroying most of the F4F-3 Wildcat fighters based on the island. Aircraft from the Mihoro Kokutai, based in French Indochina, bombed Singapore, and aircraft from the Genzan Kokutai were searching for Force Z, the newly formed British fleet in the Far East.
On 10 December the G3M2 made its most dramatic contribution to the war. Force Z was built around the capital ships HMS Prince of Wales and HMS Repulse. They were at sea in an attempt to intercept the Japanese invasion fleets heading for Malaya, or if that was not possible then to bombardment the Japanese troops on the beaches. If Force Z had included the aircraft carrier it was meant to, then this mission might have ended in success, but the carrier had run aground on the way east. On 10 December Force Z was caught by 60 G3M2 Models 21 and 22 from the Mihoro and Genzan Naval Air Corps and 26 G4M1s, and both ships were sunk.
By the end of the initial Japanese onrush the G3M had fought in the Dutch East Indies, the Philippines, Malaya and as far as Rabaul. After that the Japanese were forced onto the defensive. Rabaul would be the last important posting for the G3M. By the autumn of 1942 five G3M units were based there, taking part in the desperate fighting on Guadalcanal, but all five units would soon convert to the G4M ‘Betty’. By the start of 1943 very few G3Ms remained in front line units.
A number of other uses were found for the spare aircraft. A large number became ‘hacks’, used as general purpose transport aircraft by other units. A number of special projects used the G3M. It was to have been the glider tug for the Kugisho MXY5 assault glider.
From the end of 1943 modified G3M3 Model 23s, half equipped with radar, were used by the new Combined Escort Fleet to guard the vital Japanese shipping lanes against increasingly effective Allied attacks. In July 1944 the first MAD (Magnetic Anomaly Detection) equipped G3M3s entered service, and by the end of the war were credited with sinking 20 Allied submarines. The G3M was also used as a transport aircraft – the Kusko L3Y