JAPANESE PILOTED BOMBS

The Origin of the Ohka

The only purpose-designed suicide aircraft to reach full operational status in World War II was the Imperial Japanese Navy’s Yokosuka MXY7 Ohka (“Cherry Blossom”), which the Allies called the Baka (“Idiot”) bomb. The weapon, a piloted missile, was also known in Japan as the Jinrai (“Divine Thunderbolt”).

Credit for the origin of the Ohka is generally given to a junior officer, Ens Mitsuo Ohta, a transport pilot with the 405th Kokutai of the JNAF. However, it is fairly certain that discussion of a piloted bomb antedated Ohta’s advocacy of a rocket-propelled, manned missile early in 1944. As in the case of other suicide weapons, the high command at first put up token resistance; but when preliminary designs drawn up by Ohta with the help of the Aeronautical Research Institute, University of Tokyo, were submitted to the Dai-Ichi Kaigun Koku Gijitsusho (First Naval Air Technical Arsenal) at Yokosuka, the decision to proceed with the weapon was quickly made. It is important to note that the Ohka was approved – and the recruitment of personnel begun – in August 1944, some two months before Admiral Onishi’s formation of the first “official” kamikaze squadrons.

A team headed by LtCdr Tadanao Miki worked intensively to produce 10 operational Ohka by late September 1944, along with a number of unpowered models for flight trials. These trials, with both powered and unpowered models launched from beneath “Betty” bombers, began in October: the first powered flight was made at Kashima, near Sasebo, by Lt Kazutoshi Nagano, who declared that the Ohka handled “better than a Zero”. His enthusiasm was not shared by other test pilots; one of whom described the aircraft as “a flying coffin”. The IJN had, however, gone ahead with full production even before studying the results of the trials. Thus, the programme was not set back by the deaths in November of two test pilots: Lt Tsutomo Kariya, killed when his Ohka stalled immediately after release from its parent aircraft; and CPO Kita, killed in a crash-landing.

The Ohka Model 11

The Ohka Model 11, of which 155 were built at Yokosuka and 600 by the Dai-Ichi Kaigun Kokusho (First Naval Air Arsenal) at Kasumigaura, between September 1944 and March 1945, was the only mark carried into action. The small mid-wing monoplane, with an alloy (duralumin) fuselage and wooden wings and stabilizers, was powered by three solid-propellant rockets mounted in the fuselage aft the cockpit.

The cockpit was surprisingly well-finished for a one-trip aircraft, as Allied observers noted when undamaged Ohka were captured on Okinawa and elsewhere. The pilot’s bucket-seat was protected by 0.3–0.6-inch (7.62–15.24mm) armour plate and had a rubber-padded head rest. The controls were kept simple, since the pilots would be given little flight training: besides a control column, instrumentation comprised rocket ignition switches, compass, altimeter, turn-and-bank and airspeed indicators, and an arming handle for the fuzes at the base of the warhead (an impact fuze was also mounted at the nose). The pilot had a quick-release cockpit catch: this was purely a token gesture, for his chance of baling out during his terminal dive was nonexistent. A simple sighting ring was mounted on the fuselage immediately forward of the windshield. Forward of the sight was the suspension lug, by which the Ohka was slung beneath its carrier.

The Model 11 was designed to be carried beneath and launched from a Mitsubishi G4M2e Model 24J twin-engined bomber. In this variant of the G4M2 “Betty”, the bomb-bay doors were removed to allow carriage of the Ohka in a semi-recessed position beneath the bomber’s belly, shackled to the mother plane by its suspension lug. The Betty’s unprotected fuel tanks – armour having been sacrificed to range in its design – had already earned it the nickname of the “one-shot lighter” from US airmen: as an Ohka carrier, increased weight and degradation of handling characteristics made it even more vulnerable.

The Divine Thunderbolt Corps

Personnel for Ohka operations were recruited from among naval air units, where posters urging men to volunteer for “special attack” duties appeared in August 1944. Although the suicidal nature of the work was not concealed, volunteers were numerous: even when married men, elder and only sons and others with heavy family responsibilities were weeded out, some 600 men were quickly chosen. On 1 October 1944, antedating the formation of the first kamikaze squadrons by some three weeks, the 721st Kokutai (Naval Air Corps) – nicknamed the Jinrai Butai, “Divine Thunderbolt Corps” – was formed at Hyakurigahara Naval Air Force Base in central Honshu. The commander was Cdr Motoharu Okamura, a veteran airman who, as commander of the 341st Air Group in the Tokyo area in June 1944, had been a major advocate of the formation of kamikaze squadrons, promising Vice-Admiral Shigeru Fukudome that he would “turn the tide of war” with 300 suicide aircraft. Fukudome had reported that conversation to Vice-Admiral Seiichi Ito of the Naval General Staff – and Okamura’s enthusiasm was now rewarded. In charge of operations under Okamura were LtCdr Goro Nonaka and LtCdr Kunihiro Iwaki. In November the Jinrai Butai moved to Konoike NAFB northeast of Tokyo, where its organization was finalized. From late November, it consisted of four “Cherry Blossom Squadrons”, each at first with some 10 Ohka and 40 kamikaze Zeros. At first, the Zeros of 721st NAC were A6M5s, each carrying a 551lb (250kg) bomb; but from May 1945 the Corps was equipped with the new A6M7 Model 63, purpose-adapted for suicide attack and carrying a 1,102lb (500kg) bomb. These were nicknamed Kembu (“strengthening the warrior spirit”) bombers. The Corps’ bomber wing comprised the 708th and 711th Squadrons, each with 18 Mitsubishi G4M2e bombers as Ohka carriers. Its escort wing comprised the 306th and 308th Squadrons, each with 36 Zero fighters.

Before being expended in suicide attacks, the Zero fighters attached to each Cherry Blossom Squadron were used to train Ohka pilots. The first volunteers had been selected largely from pilots who had already received conventional training. Because of the shortage of time and fuel, their Ohka training consisted largely of familiarization with the weapon on the ground; training in attack methods while flying a Zero with the engine switched off; and, for some, a single powered flight in an air-launched Ohka fitted with landing skids and with water ballast replacing the warhead. Later in the programme, the Ohka K-1, an unpowered craft in which water ballast replaced both warhead and rocket motors, was introduced to allow less-experienced volunteers to receive limited flight training. Fortyfive K-1s were built at Yokosuka. The Ohka Model 43 K-1 KAI Wakazakura (“Young Cherry”) was a more practical trainer, for it was a two-seater (a second cockpit replacing the warhead) and was powered by a single tailmounted rocket unit; but only two of these were completed.

Combat Deployment Frustrated

The speed with which the first Ohka volunteers were trained may be judged from the initial plans for the weapon’s combat deployment.

On 28 November 1944, the newly-commissioned aircraft carrier Shinano sailed from Tokyo Bay for the Matsuyama fleet training area, near Kure. Begun as the third of the Yamato-class super-battleships, Shinano was converted to a carrier while building. On her launch, 8 October 1944, she displaced 70,755 tons (71,890 tonnes) fully loaded; with an overall length of 872.75ft (266m) and an 840ft (256m) armoured flight deck, she was the largest and best-protected carrier of World War II. She was intended as a “supply carrier” and carried only 47 aircraft for her own operational use: the greater part of her immense bulk was crammed with complete aircraft, spares and ordnance – including 50 Ohka Model 11s, the first operational batch, with which it was planned to establish bases in the Philippines. It was thought possible that Shinano herself might become such a base – a mobile airstrip from which Ohka-carrying bombers would be launched.

Shinano sailed with a young, inexperienced crew; with dockyard hands still aboard, working on her multiple watertight compartments; and without proper pumping gear. At 0310 on 29 November, still in Japanese coastal waters, she was struck by at least four torpedoes from the submarine USS Archerfish (Cdr Joseph F. Enright), which had tracked its huge quarry on the surface throughout the night. Although Shinano was badly holed, Captain Toshiro Abe held his original course at 18–20 knots for some hours: the flooding below grew worse; the civilian workers and many crewmen panicked; and by the time Abe realized the true extent of the damage, his ship was past saving. At 1055, some 120nm (138 miles, 222km) SSE of Cape Shiono, Honshu, the giant carrier rolled over to starboard and went down by the stern, taking with her Captain Abe, some 500 of his 1,400-strong crew – and the first 50 operational Ohka. Her period of commission had lasted for no more than 17 hours.

The only Ohka eventually deployed outside Japan were a number of Model 11s sent to Okinawa, where intact specimens were captured after the invasion of 1 April 1945, and to some other bases, notably Singapore. However, so far as can be ascertained, no Ohka missions were flown from bases outside the home islands.

Boosting Morale

Training at Konoike was carried on at a hectic pace, encouraged by morale-boosting visits from the IJN’s high command. Fleet Admiral Soemu Toyoda, Chief of Naval General Staff, and Fleet Admiral Osami Nagano arrived on 1 December, followed by Navy Minister Admiral Mitsumasa Yonai on 3 December. Admiral Toyoda exhorted the Ohka pilots to combat the enemy’s material superiority with their spiritual force, and presented each man with a white hachimaki, bearing the Jinrai Butai ideographs, and a short sword engraved with the recipient’s name. Early in January, when preparations were made to move to an operational base at Kanoya in southern Kyushu, the Corps pilots travelled to Tokyo to pray for success at Yasukuni Shrine, at Meiji Shrine, and outside the Imperial Palace. Informed of the impending move, Emperor Hirohito sent an aide-de-camp to Konoike with his personal good wishes.

The 1st Cherry Blossom Unit of the 721st Kokutai, commanded by Lt Kentaro Mitsuhashi following the death of Lt Kariya in flight testing, arrived at Kanoya Naval Air Base in March, ready for the Ohka’s first combat mission. All that was needed was a worthwhile target. On 21 March, one appeared: the ten heavy and six light aircraft carriers of US Task Force 58 which, on 18–20 March, had launched heavy strikes against airfields in Kyushu and the remnants of the Combined Fleet in the Inland Sea, as a preliminary to the invasion of Okinawa. Determined Japanese counter-strikes by both kamikaze and conventional bombers had resulted in damage to several carriers, and early on 21 March a Japanese reconnaissance flight reported three US carriers, apparently damaged and without protective air cover, some 320nm (368 miles, 592km) southeast of Kyushu. Vice-Admiral Matome Ugaki, commanding Fifth Naval Air Fleet, ordered Okamura to commit the Jinrai Butai to action immediately.

Date: 21 March 1945

Place: Philippine Sea

Attack by: Ohka piloted bombs

Target: USN Task Group 58.1

Okamura’s first preoccupation was to secure an adequate fighter escort for his vulnerable Betty bombers which, according to a Japanese source, were limited to a maximum cruising speed of little more than 130mph (240kmh) when burdened with the 4,718lb (2140kg) Ohka. When he found that the escort force, 201st Air Group, could provide only 55 Zeros, he sought to cancel the mission, but agreed to go ahead on Admiral Ugaki’s urging. Unwilling to stay behind while his men faced heavy odds, Okamura now declared that he himself would lead the attack. Again he was frustrated: LtCdr Goro Nonaka, chief flight officer, claimed this as his right and flatly refused to stand down in Okamura’s favour.

Eighteen Betty bombers were prepared for takeoff; 16 of them with Ohka beneath their bellies. (According to Japanese eyewitnesses, the Ohka of this first mission were painted bright blue, with the unit’s cherry blossom emblem in red on the side of the fuselage. The colour scheme reported from later missions was for the bomb’s upper surface to be painted pale green; its underside grey; and the unit marking and cherry blossom symbol – and sometimes the imperial chrysanthemum emblem, on the nose – in red. Training Ohka were normally bright orange.) Two Bettys, one the aircraft of LtCdr Nonaka, flew without Ohka. The Ohka pilot appointed to launch first and lead his comrades to their targets was Lt Kentaro Mihashi. Each pilot wore the hachimaki presented by Admiral Toyoda; Admiral Ugaki was present on the airstrip to pour the sake in which the pilots drank a toast to success. After checking the controls of their weapons, the Ohka pilots took their places beside the pilots of the parent aircraft, leaning from the windows to salute Ugaki as they taxied to takeoff at 1130 hours.

As LtCdr Nonaka entered his aircraft, he remarked ‘This is my Minatogawa” – a reference to Masashige Kusunoki’s heroic fight, with 700 men against many thousands, at the Minato River in 1336. The odds would be even greater than Nonaka expected, for of the 55 Zeros detailed to escort the Ohka force, only 30 were able to sortie: eight failed to get off the ground and 17 turned back with engine trouble. Even so, Admiral Ugaki decided not to call back the Ohka force. The 18 Bettys with their depleted escort pressed on towards their target, which was in fact, Rear-Admiral J. J. Clark’s Task Group 58.1, with the fleet carriers Hornet, Bennington and Wasp (the latter badly damaged by a kamikaze hit on 19 March, but still operational) and the light carrier Belleau Wood escorted by the battleships Massachusetts and Indiana and a strong force of cruisers and destroyers.

Ohka Operational Procedure

Although it was not followed in the mission of 21 March, the standard operational procedure for the Ohka may properly be described here.

Until reaching the target area, the Okha pilot remained in the parent aircraft. Some 50 miles (80km) from the target, having said a formal farewell to the bomber’s crew, he crawled through the bomb-bay and into the cockpit of his weapon, which was secured from the outside by a crewman. He remained in contact with the bomber pilot through a speaking tube or telephone link until the moment of launching. Then, advised by the bomber’s pilot, the Ohka pilot pulled the lever releasing the shackle from the suspension lug, aiming to launch from the mother plane at an altitude of 20–27,000ft (6100–8230m) when about 20nm (23 miles, 37km) from the target. The Ohka’s flight began as a shallow, unpowered glide, reaching a speed of 230–280mph (370–450kmh). When less than one minute away from the target, the pilot triggered the electrical ignition of his rocket motor: its 1,764lb (800kg) thrust, with a duration of 8–10 seconds, gave a maximum speed of 403mph (649kmh) at 11,500ft (3505m). In its final dive on the target, at an angle of c.50°, the Ohka reached a terminal velocity of some 580mph (933kmh). If he could, the pilot levelled out from his dive at the last moment, to strike his target at the waterline.

Such a weapon as the Ohka, with its 2,646lb (1200kg) warhead of tri-nitroaminol, was a potential killer of major warships. Once approaching its terminal velocity, it was too fast for interception by any aircraft then available, and virtually unstoppable by AA fire. Its fallibility, as its first mission so graphically demonstrated, lay in its method of delivery to the target area.

Interception and Destruction

The bombers of 721st Kokutai and their escorts were picked up by radar while still some 70nm (80 miles, 130km) northwest of the USN Task Group, and additional fighters immediately launched from the US carriers to supplement the normal CAPs. Of some 150 US interceptors airborne, the first to find the Ohka force – some 60nm (69 miles, 111km) from the US carriers – were 24 Grumman F6F Hellcats from Hornet (VF-17 and VBF-17) and Belleau Wood (VF-30).

The Ohka pilots never had the chance to enter their weapons, which were jettisoned as soon as the Bettys came under attack. Even this could not save the clumsy bombers: in a 20-minute melee all 18 were chopped down by Hornet’s Hellcats, Lt Henry E. Mitchell, Jr, of VBF-17 claiming five kills. Meanwhile, Belleau Wood’s fighters, assisted by F4U Corsairs, engaged the escorting Zeros. It is difficult to escape the conclusion that the Zero pilots were either inexperienced or had little stomach for their mission: for the loss of only one Hellcat, some 15–20 Japanese fighters were destroyed. Japanese sources state that only “one or two” Zeros returned to Kanoya to tell of the total destruction of the first Ohka mission – and the same sources say that Admiral Ugaki was seen to weep on receiving the news.

Ohka at Okinawa

The Allied invasion of Okinawa began on 1 April 1945 – and on the same day the second Ohka mission was flown. Three Bettys and three kamikaze Zeros took off from Kanoya late in the day, intending to strike at the invasion shipping after dusk and thus lessen the chances of interception. Approaching the landing fleet from the north, the Bettys were able to avoid air patrols and launch their missiles. A diving Ohka struck one of the twin 16-inch turrets of the battleship USS West Virginia, causing considerable damage and inflicting several casualties. The remaining Ohka and kamikaze aircraft succeeded in damaging the attack transport Alpine (16 killed, 27 wounded) and the cargo ships Achernar and Tyrrell.

In all, about 300 Ohka were available during April-June 1945 for attacks on Allied shipping at Okinawa. Of these, according to Japanese records, only 74 were committed to action, of which number some 56 either succeeded in making attacks or were shot down with their parent aircraft. It was difficult for the Japanese accurately to gauge the effect of Ohka sorties, since escort aircraft that approached Allied shipping closely enough to observe the attacks were unlikely to return. The Allies nicknamed the weapon the Baka(“idiot” or “foolish”) bomb. This was not altogether appropriate: because the Ohka was virtually unstoppable, when it could be successfully launched, it exerted an adverse effect on Allied morale out of all proportion to its operational success.

Date: 12 April 1945

Place: East China Sea, off Okinawa

Attack by: Ohka piloted bombs

Target: US radar picket destroyers

Apart from stepping up attacks on the Kyushu airfields from which they flew against Okinawa, the Allies’ only sure defence against the Ohka was to intercept the parent aircraft before the piloted bombs were launched. A vital role was played here by radar picket destroyers. On 12 April, in the course of the second kikusui mass attack, this cordon of ships became a target for Ohka strikes.

Eight Ohka-carrying Bettys took off from Kanoya, escorted by both kamikaze and conventional Zeros. On the way to the target area, the force split up, to approach from widely separated directions and thus lessen the chance of a single interception prejudicing the entire mission. At least four Bettys reached the Allied defence perimeter, where the radar pickets were on station. A much quoted example of the Ohka pilots’ sang-froid was the behaviour on this mission of Lt Saburo Doi, whose parent plane was the only one of the mission to return to Kanoya. Doi’s last action before boarding his Betty was to enquire into the provision of new bedding for the Jinrai Butai’s spartan living quarters. Once aboard the aircraft, he lay down on an improvised cot and, asking to be woken 30 minutes before ETA in the target area, fell asleep. Duly awoken, he remarked how quickly the time had passed, shook hands all round, entered his Ohka, and was launched from the Betty at what was thought to be the ideal range (11 miles, 18km) and altitude (18,375ft, 6000m).

Lt Doi was credited by the Japanese with a direct hit on a battleship – but although USS Tennessee and Idaho were both damaged by suicide attack on this day, USN records attribute the hits to kamikaze aircraft. No doubt exists, however, concerning the fate of the 2,200-ton “Sumner”-class destroyer Mannert L. Abele (LtCdr A. E. Parker). Manning Radar Picket 14, some 70nm (80 miles, 130km) northwest of Okinawa, along with two rocket-armed landing ships, Abele was subjected to a determined kamikaze attack at c.1440 hours. Three Zeros dived on the destroyer from different angles: one hit home, smashing into the starboard side and penetrating the after engine room before its bomb detonated, fracturing the shafts, breaking the destroyer’s back and leaving her dead in the water.

One minute later, the big destroyer was a sitting target for a diving Ohka: again she was struck to starboard, and again the attacker penetrated the ship before exploding. Abele broke in half, sinking within three minutes, with 79 men killed and 35 wounded. More would have died if LSM(R)-189 and -190 had not been on hand to pick up survivors, while engaging and shooting down two Zeros that were bombing and machine gunning men in the water. During the rescue work, a Zero crashed LSM(R)-189, wounding four of her crew.

Also hastening to the relief of Abele’s survivors was the destroyer minesweeper USS Jeffers from Radar Picket 12. At 1435, Jeffers engaged an approaching Betty bomber which released an Ohka at close range. The DMS’s fire was believed to have damaged the piloted bomb, which dived into the sea some 50yds (46m) from the ship – but even at that distance the Ohka’s detonation caused sufficient damage to send Jeffers for repair to the base at Kerama Retto.

Meanwhile, on Radar Picket 1, the destroyer USS Cassin Young had been badly damaged by a kamikaze aircraft. The destroyers Stanly and Lang were ordered to her relief, coming under kamikaze attack on the way. Within 20 minutes, as the destroyers manoeuvred beneath a CAP controlled by Stanly’s fighter-director, more kamikaze closed in, Ohka-carrying Betty bombers among them. Diving through the screen of US aircraft, and then levelling out and seemingly unaffected by numerous hits from the destroyer’s 20mm and 40mm AA guns, an Ohka struck Stanly on the starboard bow just above the waterline. The body of the Ohka tore clear through the ship and its warhead emerged through the port side before exploding. Stanly was still able to fight, and a few minutes later her gunners engaged a second Ohka. Its pilot showed great skill and determination, passing so low over the destroyer as to tear the ensign from its gaff and then attempting to bank for a second run. Concentrated 40mm fire tore a wing from the attacker, sending it into the sea some 2,000yds (1830m) away. Only three men aboard Stanly were wounded by the impact of the first Ohka – which left the remains of the Ohka pilot thinly plastered over a bulkhead within the destroyer.

On 14, 16 and 28 April, Ohka missions were sent from Kanoya against ships at Okinawa. Seven Ohka sorties were flown on 14 April without recorded success – although no Bettys returned.

On 16 April, as part of the third kikusui attack, six Ohka-carrying Bettys sortied against the Royal Navy’s Task Force 57: Rear-Admiral Philip Vian’s four fleet carriers – HMSs Formidable, Indefatigable, Indomitable and Victorious – were striking at Japanese airfields in the southern Ryukyus. Fighter-director teams on the carriers picked up the fast-moving Ohka on radar, but no attempt at interception was necessary: the piloted bombs had been launched too far from their targets and splashed harmlessly into the sea. It is probable that the same fate befell the four Ohka sorties made from Kanoya on 28 April.

The Ohkas Limited Range

From the foregoing instances, it may be inferred that the effective range of the Ohka was far less than the 50 miles (80km) attributed to them in some non-Japanese sources – and less even than the Japanese figure of 20-plus miles (32+ km). They proved effective only when launched at close range – some 10 miles (16km) or less – at times when Allied CAPs were fully occupied in beating off kamikaze and conventional aircraft. The chronic shortage of aviation fuel and pilots for escort aircraft meant that, when committed independently of mass kamikaze attacks, the Ohka were usually shot down with their parent aircraft or wasted by launching at extreme ranges.

However, on 4 May during the fifth kikusui offensive, the Ohka were used effectively. Seven Ohka-carrying Bettys took off from Kanoya for Okinawa, where heavy air attacks had been made on Allied shipping from dawn onwards. Shortly before 0900, a single Betty was sighted about 5nm (5.75 miles, 9.25km) from Radar Picket 14. CAP aircraft were directed to the bomber, which succeeded in launching its Ohka before it was knocked down. A smoke haze from the transports off the Hagushi beaches limited surface visibility to less than 2,000yds (1830m), and the Ohka’s track was lost until it burst from the murk only 1,000yds (915m) from the picket ships. Undeterred by 40mm fire, the Ohka steered into the light minelayer USS Shea, its tremendous velocity taking it through the starboard bridge structure to detonate on the port side. With her upper works a mangled wreck, 27 men dead and 91 wounded, Shea was able to reach the Hagushi anchorage, but took no further part in the war. Later that morning, a little farther north, the minesweeper USS Gayety had two men wounded when she was near-missed by an Ohka. A single Betty bomber returned to Kanoya from this mission.

Date: 11 May 1945

Place: Okinawa

Attack by: Ohka bombs and kamikaze aircraft

Target: US radar picket ships

The Ohka’s last successful mission – proving again the potential of the weapon when used as one element of mass kamikaze attack – was flown on 11 May, when four Bettys (one of which returned after launching its Ohka) sortied during the second and final day of the sixth kikusui offensive.

On Radar Picket 15, the destroyers Evans (Cdr R. J. Archer) and Hugh W. Hadley (Cdr B. J. Mullaney), the latter acting as fighter-control ship, along with three landing ships, fought one of the fiercest anti-kamikaze actions of the battle of Okinawa. Between 0750 and 0930, it was estimated that some 50 enemy aircraft were destroyed by the 12 Corsairs of the picket station’s CAP, while at least 50 more evaded the air cover and struck at the ships. While manoeuvring at high speed, Evans and Hadley were subjected to repeated attacks by groups of four to six kamikaze coming in from different angles. At 0920, Hadley’s gunners were engaged with ten aircraft simultaneously: four to starboard, four to port, two astern. All ten were destroyed, but the destroyer sustained a bomb hit and a kamikaze crash aft, followed by a hit from an Ohka released by a low-flying Betty at very close range. Holed and flooding, with 28 men dead and 67 wounded, Cdr Mullaney gave the order to abandon ship; but a skeleton crew remained aboard and brought under control the fires that threatened Hadley’s magazines. With Evans, which had taken four kamikaze hits, Hadley was towed to Kerama Retto and later scrapped. The two destroyers’ gunners were credited with the destruction of 46 enemy aircraft in less than two hours.

On 24 May, as the seventh kikusui offensive raged at Okinawa, the carrier pilots of US Task Force 58 struck at the kamikaze’s airfields on Kyushu. The Jinrai Butai’s base at Kanoya was a prime target: US pilots claimed the destruction of 70 Betty bombers awaiting takeoff with Ohka beneath their bellies. Such a total seems unlikely – and the raid did not prevent a sortie the next day by 11 Ohka-carrying Bettys, when Admiral Toyoda was present to bid the suicide pilots farewell as they took off for Okinawa at 0500 hours.

Approaching the target area, a heavy and prolonged squall cut down visibility so far – it was reported as nil to below 4,000ft (1220m) – that a number of the Bettys jettisoned their Ohka and returned to base; only to be forced to land at a nearby Army base when Kanoya was found to be again under attack. One Betty, however, pressed on. Disregarding standing orders that forbade Ohka to launch below 15,000ft (4570m), the Betty came down almost to sea level for a run in on Radar Picket 5 – but was shot down by the combined fire of the destroyers Braine and Anthony before the Ohka could launch.

The Last Ohka Mission

On 22 June, the second and last day of the tenth and final kikusui offensive, the last Ohka mission of the war was flown by six Bettys of the 10th Cherry Blossom Unit. The chief Ohka pilot was Lt Toshihide Fujisaki; but neither he nor his comrades found a target. Two of the Bettys returned safely to base.

The total losses of the Jinrai Butai, almost all incurred during the kikusui attacks at Okinawa, are given in Japanese sources as 467 men; of whom some 55–60 were Ohka pilots and 229 the pilots and crews of parent aircraft. An Allied estimate of 298 Ohka expended is almost certainly an overstatement: if it is accepted as in any way accurate, it must be concluded that far more Ohka were shot down with their parent aircraft or jettisoned than ever achieved operational launching. The Ohka sank one destroyer (Mannert L. Abele) and shared in damaging another (Hugh W. Hadley) so badly that she was scrapped; a light minelayer was so badly damaged as to take no further part in the war, and damage of varying degree was inflicted on a battleship, a destroyer, a destroyer-minesweeper, a minesweeper, an attack transport and a cargo ship. The deaths of some 150 American sailors and the wounding of about 250 may be attributed to Ohka attacks.

Ohka in the Final Defence

Following the mission of 22 June, the remaining Ohka were redeployed in the home islands to meet the expected Allied invasion. It was planned to establish a chain of small bases along the coasts from which Ohka, carried by bombers or launched from catapults, could sortie against invasion shipping. Launching catapults for the Ohka Model 43B (described below) were to be mounted in natural or specially excavated caves facing potential landing beaches; and a pilot-training centre for this weapon was established at a requisitioned Buddhist monastery on a mountain near Kyoto, Honshu.

Of the Cherry Blossom Units already operational, some remained at Kanoya, but most were moved to Komatsu Air Base in central Honshu, while the kamikaze aircraft units allied to them went to Matsuyama Air Base on Shikoku. The main training echelon – Squadron I, commanded by Lt Akira Hirano – continued its work at Konoike, where Hirano strove to bring a new, 300-strong operational unit – 722nd Naval Air Corps (called Tatsumaki Butai, “Tornado Corps”) – to operational readiness.

On 15 August, Emperor Hirohito’s broadcast of the decision to surrender put an end to all these activities. Like many other officers of the “special attack” forces, the Jinrai Butai’s commanding officer, Cdr Motoharu Okamura, decided that honour demanded expiation of his “failure”: he committed seppuku in the traditional manner.

Non-Operational Ohka Models

At the war’s end, several Ohka models were under construction or in development, although none achieved operational status. The only one built in any quantity – apart from the unpowered K-1 training glider; 45 completed – was the Model 22, 50 examples completed.

Since the Betty bomber had proved so vulnerable as a carrier, the Ohka Model 22 was designed to be carried and launched by a variant of the much faster and more manoeuvrable Yokosuka P1Y “Frances”. The P1Y3 Model 33, with an enlarged fuselage and increased wingspan to operate the Ohka Model 22 and the projected Model 21 (with the rocket engine of the Model 11 and the smaller dimensions of the Model 22), was planned to have a maximum speed of 340mph (547kmh) and a range of more than 4,000 miles (6440km). The aircraft never left the drawing board.

Even had the P1Y3 become available, it is doubtful whether the Ohka Model 22 would have been successful. Its designers aimed at improved range and, of necessity, smaller dimensions – achieving both, but at heavy cost. By using a Campini-type, 551lb (200kg) thrust, Tsu-11 jet engine, with a 100hp Hatsukaze (“Fresh Wind”) piston engine as a compressor, the Model 22 achieved a range of c.80 miles (130km), nearly four times that of the Model 11. But its maximum speed was only about 276mph (444kmh), which would have made it extremely vulnerable to both interception and AA fire after launching. Its warhead was only half the size of that of the Model 11.

A one-third reduction in wing area meant that the handling characteristics of the Model 22 were far worse than those of the Model 11, itself a tricky aircraft. It was impossible to land the Model 22, which had a stalling speed of 207mph (333kmh); for testing flights, its pilot was equipped with a special parachute and instructed to bale out at 3,000ft (914m). On 26 June, Lt Kazutoshi Nagano, chief Ohka test pilot, was killed when a Model 22 launched from a P1Y1 at 12,000ft (3660m) went out of control immediately: Nagano escaped from the rolling, diving Ohka but received mortal injuries when his parachute failed to open fully. But although flight testing was never satisfactorily completed, the Model 22 was put into production: the Dai-Ichi Kaigun Kokusho planned to build the weapon in underground workshops, dispersed to escape the effects of US bombing.

The Ohka Model 21, combining the rocket motor of the Model 11 with the airframe of the Model 22, was never built; and nor were the projected Models 33, 43A and 43B, which were to be powered by the Ne-20 axial-flow turbojet, a 1,047lb (475kg) thrust engine.

The Model 33, about the same size as the Model 11, was intended to be launched from the Nakajima G8N1 Renzan (“Mountain Range”), but only four of these four-engined heavy bombers, called “Rite” by the Allies, were completed.

The much larger Model 43A (with folding wings) was intended to be catapult-launched from a fleet submarine; the Model 43B was to be catapult-launched from shore installations. Yet another method of delivery was envisaged for the projected Model 53, which was to be towed aloft by a bomber and released on sighting a target.