Subscribe now for full access and no adverts
The Japanese armed forces gave their suicide aircraft many designations, but this article uses the generally accepted term kamikaze (‘divine wind’). The term was originally used to describe the typhoons which destroyed the Mongol fleets sent by Kublai Khan to invade Japan in 1274 and 1281.
In 1944, Japan’s forces suffered a run of disasters in the Pacific theatre, where Allied forces were overrunning key islands to provide air bases for a strategic bombing campaign against the Japanese home islands. The Allies’ advance also cut Japan off from the bulk of its oil supplies, which were drawn from the former Dutch East Indies (modern Indonesia). The loss of at least 550 Japanese aircraft in the Battle of the Philippine Sea in June 1944 led to drastic reassessments of how air power could most effectively be employed against seemingly overwhelming Allied naval and air superiority.
This disaster swung the balance in favour of the concept of aircraft making suicide attacks, which had been under discussion at Japanese Imperial GHQ since 1943. By the autumn of 1944, the first kamikaze units had formed, equipped with A6M5 ‘Zero’ fighters, each modified to carry a single 250kg (550lb) bomb. Initially, the bombs were clamped to the aircraft, but conventional bomb racks were soon fitted as it was realised that more damage could be inflicted if the bomb was released just before the aircraft hit the target vessel.
The first organised kamikaze attacks were launched on 25 October 1944, the second day of the Battle of Leyte Gulf, in the Philippines, when a total of 55 kamikaze attacked several US escort carriers, sinking the St Lo and damaging the Santee, Suwanee, Kalinin Bay, Kitkun Bay, and White Plains. The effectiveness of this operation led to a massive expansion of the kamikaze campaign, using a variety of adapted aircraft. At one extreme, there were modern high-performance types such the Mitsubishi Ki-67, armed with either two 800kg (1,760lb) bombs or an internal 2,900kg (6,400lb) warhead, at speeds of up to 537km/h (334mph). In complete contrast, slow training aircraft were also modified for the role, including the Kyushu K11W, carrying a single 250kg (550lb) bomb at less than 175km/h (109mph).
Both sides recognised the potential of kamikaze attacks and raced to develop new tactics – the Japanese published manuals including recommended altitudes, diving angles, and speeds for each type of aircraft. The most destructive was an approach at an altitude of about 6,100 metres (20,000ft), followed by a shallow dive on sighting the target, culminating in a near-vertical crash-dive from a height of about 1,500 metres (5,000ft). This meant that radar-controlled heavy AA guns were forced to fire ‘blind’ during the final stage of the attack, while the aircraft’s high terminal velocity maximised damage. Fortunately for the Allies, many of the poorly trained kamikaze pilots lacked the skill to make this sort of attack, relying on simple dives directly on their targets at angles of no more than 30°.
Analysis of early kamikaze attacks showed that they were far more effective than conventional air strikes:
Conventional attacks
Three hundred planes sortie, of which 180 (60%) are lost to Combat Air Patrol (CAP). This leaves 120 to attack ships, of which 40 (33.3%) are lost to AA fire. Twelve achieve hits or damaging misses on ships (10%) and 80 return to base – meaning that total losses of 220 planes are required to score 12 hits.
Kamikaze attacks
Here, just 60 planes sortie, of which 36 (60%) are lost to CAP. This leaves 24 to attack ships, of which 12 (50%) are lost to AA fire. The remaining 12 hit their targets, with the result that none return to base – making a total of 60 planes lost to score 12 hits.
The Americans responded to this new threat by increasing the proportion of fighters in the air wings of their fleet carriers: the Essex-class carriers had carried about 40 fighters, 36 dive bombers, and 18 torpedo bombers, but this was drastically altered, with many carrying more than 70 fighters plus fewer than 30 dive/ torpedo bombers. To counter night- time kamikaze attacks, USS Enterprise and USS Independence operated a mix of radar-equipped Avenger torpedo bombers and Hellcat fighters.
All Allied ships in the Pacific also had their AA armament strengthened as far as possible, with the 5in (127mm) dual-purpose guns that armed most US warships having priority for supplies of proximity-fused ammunition – with each round containing a miniature radio transmitter/receiver which detonated the shell when the proximity of the target caused the signals to reach a pre-set frequency. It was calculated that it took an average of 1,162 conventional, time-fused 5in AA rounds to destroy each kamikaze, but this was reduced to 310 rounds per ‘kill’ with proximity-fused shells. Occasionally, ships did far better than this – in May 1945, the destroyer escort (frigate) Abercrombie shot down a kamikaze with just two rounds.
One of the largest kamikaze campaigns took place during the Battle of Okinawa (April-June 1945), in which the Japanese launched a total of ten major offensives against the Allied invasion fleet and the covering Task Forces off the island of Okinawa under the generic title Kikusui. In these main attacks, some 9,400 sorties were flown and 1,320 machines were lost; 1,840 of these sorties were suicide missions in which 960 participating aircraft were destroyed, either by the Allied defences or by striking their targets.
The intensity of the campaign emphasised the contrast in vulnerability between the British and US carriers – although the British Pacific Fleet was the target of repeated kamikaze attacks, its carriers with their armoured flight decks proved to be far more resilient than their American counterparts. This was emphasised on 1 April 1945, when HMS Indefatigable was hit by a Zero carrying a 250kg (550lb) bomb. The carrier was struck on the forward crash barrier, where the flight deck joined the island. The exploding bomb and aircraft smashed the sickbay, briefing room, and a flight-deck crash barrier. However, the armoured flight deck absorbed much of the blast, which blew a ‘dent’ roughly 75mm (3in) deep over a 4.5m (15ft) area. Indefatigable was operational after no more than 40 minutes – one of the ship’s USN Liaison Officers famously remarked: ‘When a kamikaze hits a US carrier, it’s six months repair at Pearl. In a Limey carrier, it’s a case of “sweepers, man your brooms”.’
The greater vulnerability of American carriers was demonstrated on 11 May 1945, when USS Bunker Hill was struck by two kamikaze Zeroes – the first emerged from low cloud, and dropped a 250kg (550lb) bomb, which penetrated the flight deck and exited from the side of the ship at gallery deck level before exploding in the sea. The Zero then crashed into the carrier’s flight deck, destroying parked aircraft, which were fuelled and armed, starting a large fire. Barely 30 seconds later, a second Zero dropped another 250kg (550lb) bomb before hitting the flight deck. Bunker Hill’s casualties totalled 396 dead and 264 wounded. The carrier was sent to the Bremerton naval shipyard, in Washington, for repairs which were not completed until September 1945.
The attacks off Okinawa included a total of 185 made by Yokosuka MXY-7 Ohka piloted flying bombs. The type carried a 1,200kg (2,600lb) warhead and was powered by three Type 4 Model 1 Mark 20 solid-fuel rocket motors – which had a total burn time of only 24 seconds, but which gave it a maximum speed of 926km/h (575mph) in a terminal dive. Although the Ohka’s small size and high speed made it a very hard target for Allied fighters and AA fire, its weakness was a very short effective range of no more than 16km (10 miles) – which meant it had to be carried to the immediate target area by an adapted bomber, the Mitsubishi G4M2e Model 24 Tei ‘Betty’. This combination was slow, with poor manoeuvrability, making it a ‘sitting duck’ for all Allied fighters, which destroyed the majority of Ohkas before they could be launched. (The type did sink one American destroyer – Mannert L Abele – and damaged a second – Hugh W Hadley – so badly that she had to be scrapped. Lesser degrees of damage were also inflicted on a battleship, a destroyer, two minesweepers, an attack transport, and a cargo vessel.)
The last Ohka mission of the war was flown on 22 June 1945, after which the remaining aircraft (and most other kamikaze types) were held back to counter the expected invasion of the Japanese home islands. New versions were under development at the end of the war, including the jet-powered Model 43B with a range of up to 280km (175 miles), which was designed for catapult launching from coastal sites. The last Allied vessel to be sunk by a kamikaze was the destroyer USS Callaghan, which was hit by a K5Y2 biplane on 28 July 1945. The aircraft’s two 30kg (66lb) bombs detonated Callaghan’s AA ammunition and she sank in no more than 90 minutes with the loss of 47 dead and 73 wounded.
The ‘other’ Kamikaze: from human torpedoes to ‘banzai charges’
Kamikaze air attacks on Allied shipping were just one of a number of suicide attack methods used by Japanese forces. Other less well-known examples of such weapons include:
Kaiten
A manned torpedo primarily intended for launching from submerged submarines. It was essentially an enlarged Type 93 ‘Long Lance’ torpedo fitted with a 1,550kg (3,420lb) warhead. Over 300 were built, more than 100 of which were used operationally. The type was hard to control and its only confirmed sinkings were the fleet oiler USS Mississinewa anchored at Ulithi, in the Caroline Islands, on 20 November 1944, with the loss of 63 men; an infantry landing craft (LCI-600), with the loss of three men; and the destroyer escort USS Underhill on 24 July 1945, with the loss of 113 men.
Koryu
This was a five-man midget submarine, initially designed with two torpedo tubes, but adapted to carry a warhead in the bows for a ramming attack. A total of 115 were completed, with a further 496 under construction at the end of the war, although none were used in action.
Kairyu
More than 750 of these midget submarines were ordered and over 200 had been completed by the end of the war, although there are no records of any being used operationally. They had a two-man crew and carried two 450mm (18in) torpedoes in drop collars plus an impact-fused 600kg (1,300lb) bow-mounted explosive charge intended for a final ramming attack.
Shinyo
Almost 6,200 of these explosive motorboats (EMBs) were produced for the Imperial Japanese Navy. They were small, one-man, wooden-hulled craft with a maximum speed of 48km/h (26 knots) and an impact-fused warhead of 250-300kg (550-660lb) in the bows. Some boats were also fitted with launch rails for two 120mm (4.7in) spin-stabilised rockets with incendiary shrapnel warheads, intended to suppress fire from target vessels as the Shinyo made their ramming attacks.
Maru-ni
A deep-seated rivalry with the navy led the Imperial Japanese Army to develop the Maru-ni as its own version of the Shinyo for coast defence duties, with an estimated 3,000 being completed by the end of the war. The main difference from the naval design was that each carried a single 200kg (440lb) depth charge instead of an impact-fused warhead. The recommended attack method was for several Maru-ni to make a high-speed approach to within a few metres of the target vessel before dropping their depth charges, which were set to explode after a four-second delay. Two or three depth charges detonating close to the target’s hull could sink or seriously damage all but the largest vessels – though, in practice, ramming attacks were frequently made to ensure that the depth charges exploded directly below their targets. The majority of the Shinyo and Maru-ni produced were held back for the defence of the Japanese home islands.
Ramming raids
The first B-29 Superfortress raids on Japan in mid-1944 showed that the bombers’ high-altitude performance made them very difficult to intercept. In response, Japanese fighter units experimented with a variety of unconventional attack methods, including ramming. The first successful attack was made in late August 1944, when B-29s from Chinese airfields bombed the steel factories at Yawata. Sergeant Shigeo Nobe rammed a Superfortress with his Kawasaki Ki-45 and debris from the explosion brought down another B-29. After several other successes, dedicated special attack (ramming) units were formed in November 1944, equipped with a variety of fighters which had been stripped of all non-essential equipment to improve their speed and manoeuvrability. These had limited success, although a few pilots beat the odds by surviving – notably on 3 December 1944, when three Ki-61 fighters piloted by First Lieutenant Toru Shinomiya, Sergeant Masao Itagaki, and Sergeant Matsumi Nakano intercepted a B-29 raid. Shinomiya rammed a bomber, but managed to land his badly damaged Ki-61; Itagaki had to parachute from his damaged fighter after attacking another B-29; while Nakano rammed a third bomber and crash-landed in a field. All three pilots received Japan’s highest gallantry award, the Rikugun Bukokisho (Badge for Military Merit).
Airborne operations
By 1944, the remnants of the Japanese airborne forces were limited to small-scale suicidal attacks in an attempt to reduce the intensity of the US strategic bombing campaign. On the night of 24/25 May 1945, 12 converted Ki-21 bombers took off from Kyushu carrying 136 officers and men of the Giretsu Kuteitai (Heroic Paratroopers) to attack the airfields at Yontan and Kadena on Okinawa, which had just been captured by US forces. Four aircraft aborted the mission with engine problems, and three more were shot down; however, five managed to reach Yontan during the confusion caused by a diversionary air raid. Four of the five were destroyed, but the sole survivor crash-landed and 12 raiders caused havoc, destroying a total of 70,000 US gallons (260,000 litres) of fuel, as well as blowing up nine aircraft and damaging 29 more. Only one member of the raiding party survived, escaping to reach Japanese lines on 12 June.
‘Banzai charges’
These assaults were named after the war cry Tenno heika banzai – ‘May the Emperor live for 10,000 years!’ They were all-out attacks in which Japanese troops became nikudan (‘human bullets’) intent on inflicting as much damage as possible on the enemy before dying in battle. On 29 May 1943, the 1,000 or so survivors of the 2,600-strong garrison of Attu, in the Aleutian Islands, launched just such a charge against a US invasion force of 11,000 men. When it became obvious that the assault had failed, at least half of the attackers deliberately blew themselves apart with their last grenades – only 28 Japanese prisoners survived. There was even a ‘tank banzai charge’ – in April 1945, in one of the last actions of the Japanese 2nd Armoured Division in the Philippines, two tanks (a Type 95 and a Type 97) were fitted with large, impact-fused charges and rammed American M4 Shermans, destroying at least two.
Assessment
Allied commanders with first-hand experience of kamikaze attacks had no doubts about their effectiveness. Two of Admiral Raymond A Spruance’s flagships (USS Indianapolis and USS New Mexico) were hit by kamikaze and he later wrote: ‘This is my second experience with a suicide plane making a hit on board my own ship, and I have seen four other ships hit near me. The suicide plane is a very effective weapon, which we must not underestimate. I do not believe anyone who has not been around within its area of operations can realise its potentialities against ships. It is the opposite extreme of a lot of our Army heavy bombers who bomb safely and ineffectively from the upper atmosphere.’
Just after the war, the motivation of the kamikaze was summarised by Lieutenant General Torashiro Kawabe, the deputy chief of the Imperial Japanese Army General Staff: ‘We believed that our spiritual convictions and moral strength could balance your material and scientific advantages. We did not consider our attacks to be “suicide”. The pilot did not start his mission with the intention of committing suicide [in the sense of killing himself in a spirit of despair]. He thought of himself as a human bomb which would destroy part of the enemy fleet… [and] died happy in the conviction that his death was a step towards final victory.’
David Porter worked at the Ministry of Defence for many years, and is the author of 11 books on the Second World War. He is a regular MHM contributor.
In the next issue of MHM: Operation Downfall: David Porter examines the Allied plan for the WWII invasion of Japan.
All images: Wikimedia Commons, unless otherwise stated
