By 1939, the Imperial Japanese Navy (IJN) had developed the Kantai Kessen (Decisive Battle Doctrine), an offensive/defensive doctrine in support of planned offensives to seize the vital tin, rubber, and oil resources of Malaya and the Dutch East Indies.
As it was assumed that these attacks would bring the United States into the war in support of Britain and the Netherlands, the Philippines were also targeted in order to eliminate the US Asiatic Fleet and the American air bases, which could threaten the primary Japanese offensives.
The Japanese anticipated that the US Pacific Fleet would sortie from its West Coast bases to relieve the beleaguered American garrison of the Philippines. IJN submarines would make the initial attacks before being joined by long-range bombers as the Americans came within range of Japanese air bases in the Marianas and Caroline Islands.
The IJN’s aircraft carriers would then launch airstrikes against their US counterparts, whilst Japanese destroyer flotillas made night attacks using the powerful ‘Long Lance’ torpedoes. Finally, Japanese battleships would move in to defeat the remnants of the Pacific Fleet.
Even before the war, this plan proved to be impractical – a 1939 exercise showed that the Japanese submarine force was too small to fulfil its intended role and that its maximum surface speed was insufficient to allow it to make the repeated attacks required to seriously weaken the Americans.
The horrified naval staff ran a further exercise with the rules altered to assist the submarines, but even this was not enough to achieve the predicted success when the plans were tested.
Despite this, the Kantai Kessen remained essentially unchanged until Admiral Isoroku Yamamoto was appointed as C-in-C of the Combined Fleet (the IJN’s main striking force) in August 1939.
As a former commander of the carrier Akagi, he had a greater appreciation of the potential of naval aviation than many of his contemporaries and was opposed to the policy of building ‘super battleships’ such as the Yamato-class, which he believed to be a misuse of scarce resources.
Yamamoto emphasised that the Kantai Kessen doctrine had never worked out in wargames and exercises, and proposed an alternative strategy of a pre-emptive strike to cripple the US Pacific Fleet, which would give time for the seizure of the Philippines, Malaya, and the Dutch East Indies.
He was one of the very few senior IJN officers to have any detailed knowledge of the US Navy and American industry, having studied at Harvard University (1919-1921) and served twice as naval attaché in Washington. This experience convinced him that Japan had to seek a quick victory before the USA could use its industrial strength to create overwhelming military, naval, and air superiority.
Pearl Harbor’s vulnerability
Yamamoto’s pre-emptive strike might well have proved to be impossible if the US Pacific Fleet had remained at its West Coast bases of San Pedro and San Diego, but in mid 1940 Roosevelt moved the fleet to Pearl Harbor, Hawaii, which he believed would act as a deterrent to Japan.
In military terms, the redeployment was highly risky, as the base’s vulnerability had been noted as early as 1925, when General ‘Billy’ Mitchell of the US Army Air Service issued a report entitled ‘Winged Defense’ on the threat posed by growing Japanese air power.
He envisaged an initial attack on Pearl Harbor with a follow-up strike against US bases in the Philippines, suggesting that the damage inflicted on the US Pacific Fleet would allow the Japanese to invade the Philippines months before the Americans could make any effective counter-attack.
In February 1932, Rear-Admiral Harry Yarnell demonstrated the validity of Mitchell’s warning in a major exercise in which he defied accepted wisdom by leaving his battleships behind and using only the carriers Lexington and Saratoga, escorted by a handful of destroyers.
At dawn on Sunday 7 February, Yarnell’s 152 aircraft ‘attacked’ from the north-east, just as the Japanese would almost ten years later. The ‘weapons’ used were flares and flour bombs, but the results were sufficiently convincing for the exercise umpires to rule that the army’s airfields had been put out of commission before any defending fighters could take off and that every ship in the harbour had been sunk.
The exercise was largely ignored by the US Navy, but made a far greater impact in Japan, where it was incorporated into the curriculum of the IJN Naval Academy. In 1936, its final exam included the question: ‘How would you carry out a surprise attack on Pearl Harbor?’
Evidence of the base’s vulnerability continued to grow. In 1938, Vice-Admiral Ernest King repeated Yarnell’s feat by making a near-identical raid during that year’s attack exercise, but this was again ignored by the US Navy’s hierarchy.
Yamamoto began considering a carrier strike against Pearl Harbor in March or April 1940, but won assent to formal planning and training for an attack from the IJN’s General Staff only after prolonged arguments, including a threat to resign his command.
Full-scale planning was underway by the early spring of 1941, encouraged by the successful British air attack on the Italian fleet at Taranto in November 1940 by 21 obsolete Swordfish, which succeeded in disabling three Italian battleships and damaging a heavy cruiser and two destroyers.
The details of the raid were carefully analysed – Lieutenant-Commander Takeshi Naito, the assistant naval attaché in Berlin, flew to Taranto to make preliminary investigations, which were followed by a detailed assessment by a team of IJN officers in May 1941.
The rapid growth of the IJN’s carrier force meant that its attacks could be made in far greater strength than the Taranto raid. By late 1941, the Kido Butai (‘striking force’) could deploy six fleet carriers whose combined air wings totalled over 400 aircraft. These air wings included the most advanced carrier aircraft of the day, the Mitsubishi A6M2 ‘Zero’ fighter, the Aichi D3A1 ‘Val’ dive-bomber, and the Nakajima B5N2 ‘Kate’ torpedo-bomber.
The Zero was superbly manoeuvrable. Captain Eric Brown, the Royal Navy’s chief test pilot, was highly impressed by the Zero, recalling that, ‘I don’t think I have ever flown a fighter that could match the rate of turn of the Zero. The Zero had ruled the roost totally and was the finest fighter in the world until mid-1943.’
The Val was the Japanese equivalent of the Stuka, capable of delivering a 250kg bomb with great accuracy, whilst the Kate was a versatile attack aircraft, able to operate as both a conventional bomber and a torpedo bomber.
There were numerous technical problems to be solved, including how to avoid air-launched torpedoes burying themselves in the mud beneath the shallow waters of Pearl Harbor, which was only solved by last-minute modifications.
Although torpedoes were the most effective weapon against capital ships, they could not be used against all the US battleships, which were moored in pairs in ‘Battleship Row’. Bombing was the only way of attacking the inner ships at the dockside, but the Vals could not carry a bomb capable of penetrating their armoured decks.
The Kate’s maximum bomb load was 800kg, which would be adequate, but there was no such armour-piercing bomb in the IJN inventory. The problem was finally resolved by inspired improvisation – obsolete 40cm armour-piercing (AP) shells were used as the basis for the Type 99 No 80 Mk 5 bomb, which could penetrate 150mm of armour when dropped from 3,000 metres.
The technical difficulties inherent in the operation added weight to the arguments of the more conservative admirals, who were appalled at its risks. Wargames indicated that surprise was essential to prevent crippling losses, and there was an understandable reluctance to accept that this was feasible, given the long voyage from Japan to Hawaii.
Yamamoto argued that careful routing to avoid the main shipping lanes would minimise the risk, but he and his entire staff had to threaten to resign before the sceptics would finally authorise the operation and the inclusion of six of the IJN’s most powerful carriers – Akagi, Kaga, Soryu, Hiryu, Shokaku, and Zuikaku.
In December 1941, Pearl Harbor was unprepared for an attack, despite weeks of intense US press speculation about imminent war with Japan. Lieutenant-General Walter Short had overall responsibility for the defence of Hawaii, whilst Major-General Frederick Martin was C-in-C of the Hawaiian Air Force. They controlled six radar stations, over 200 Army aircraft, and 86 heavy AA guns. (Only 20 of the authorised 140 M1 37mm AA guns had been delivered, without ammunition!)
The entire defence was crippled by a general lack of cooperation between the Army and the Navy. Admiral Kimmel, commanding the Pacific Fleet, had only reluctantly agreed that his PBY Catalina flying boats should take over long-range reconnaissance patrols as the Air Force had too few suitable aircraft.
However, Kimmel failed to notify either Short or Martin that he was only prepared to order limited patrols to the south and west of the islands, which opened the way for the Japanese force to approach from the north without being detected.
Even Short and Martin disagreed. Short was obsessed with the idea that sabotage by agents in the islands’ Japanese community posed the greatest threat, and he ordered that all aircraft should be lined up wingtip to wingtip on their airfields to make them easier to protect, with all ammunition centrally stored and guarded.
Martin had to obey and was deluged with protests from his squadron commanders, who were horrified at making their aircraft sitting targets and unsuccessfully demanded that they should instead be dispersed.
At dawn on Sunday 7 December, the six carriers of the IJN’s First Carrier Striking Force began to launch their aircraft. All aircrews had been given the following orders regarding target priorities: ‘Targets for attack are airfields; aircraft carriers; battleships, cruisers and other warships; merchant shipping; port facilities and land installations, in that order.’
A total of 408 aircraft were operational, of which 360 were in the two attack waves, with 48 Zeros assigned to protect the carriers.
The first wave comprised:
• 49 Kates armed with Type 99 AP bombs; a further 40 Kates carrying Type 91 torpedoes. (Targets: carriers and battleships.)
• 51 Vals carrying 250kg bombs. (Targets: aircraft at Ford Island, Hickam Field, Wheeler Field, Barber’s Point, and Kaneohe.)
• 43 Zeros acting as escorts with a secondary ground-attack role.
The second wave comprised:
• 54 Kates armed with 250kg and 60kg bombs. (Targets: aircraft at Ford Island, Hickam Field, Wheeler Field, Barber’s Point, and Kaneohe.)
• 78 Vals loaded with 250kg bombs. (Targets: carriers and cruisers.)
• 35 Zeros acting as escorts with a secondary ground-attack role.
The air attacks were to be backed up by five two-man Type A midget submarines (each armed with two 450mm Type 97 torpedoes) launched from fleet submarines lying offshore.
At least four of the five failed to penetrate the anchorage. At 0645, the destroyer Ward reported attacking and sinking a submarine in the restricted area just outside the harbour. This was over an hour before the first Japanese aircraft arrived and should have ensured that the defences were alerted in ample time to decimate the attackers.
All the midget submarines were lost. Although most assessments indicate that none of them achieved anything, it is possible that one did get through to torpedo the battleships West Virginia and Oklahoma.
There was a final unheeded warning at 0702, when radar operators detected a large formation of aircraft 210km north of Hawaii and phoned through a report to the Air Information Center at Fort Shafter. The inexperienced Duty Officer assumed that they had seen the 16 B-17s that were flying in from San Francisco that morning and told them to stand down.
As a result, the first Japanese aircraft achieved complete surprise when they attacked at 0755. Only eight defending fighters managed to take off and intercept, destroying a total of 12 attackers.
All eight were themselves shot down and the Japanese were able to take full advantage of the sitting targets provided by the mass of aircraft parked in the open on the island’s airfields. In all, out of 402 American aircraft in Hawaii, 188 were destroyed and 159 damaged, 155 of them on the ground.
Without any effective fighter opposition, the first attackers were able to pick their targets with minimal distraction from sporadic AA fire. As none of the Pacific Fleet’s three carriers were in port, the torpedo-bombers concentrated their attention on the battleships, with the support of the Kates armed with Type 99 AP bombs.
The accuracy of later attacks was reduced by the smoke from the first targets and far heavier AA fire, but, in all, 21 ships were damaged or lost, of which all but three were repaired and returned to service.
Arizona: hit by four AP bombs; exploded; total loss; 1,177 dead.
Oklahoma: hit by five torpedoes; capsized; total loss; 429 dead.
West Virginia: hit by two bombs, seven torpedoes; sunk; returned to service July 1944; 106 dead.
California: hit by two bombs, two torpedoes; sunk; returned to service January 1944; 100 dead.
Nevada: hit by six bombs, one torpedo; beached; returned to service October 1942; 60 dead.
Pennsylvania: in dry dock with Cassin and Downes; hit by one bomb and debris from USS Cassin; remained in service; nine dead.
Tennessee: hit by two bombs; returned to service February 1942; five dead.
Maryland: hit by two bombs; returned to service February 1942; four dead.
Utah: de-militarised battleship (target/AA training ship); hit by two torpedoes; capsized; total loss; 64 dead.
Helena: hit by one torpedo; returned to service January 1942; 20 dead.
Raleigh: hit by one torpedo; returned to service February 1942.
Honolulu: near miss; minor damage; remained in service.
Cassin: in dry dock with Downes and Pennsylvania; hit by one bomb; burnt out.
Downes: in dry dock with Cassin and Pennsylvania; destroyed after burning oil from Cassin detonated ammunition and torpedoes.
(Both ships’ hulls were damaged beyond repair but machinery and equipment were salvaged and sent to Mare Island Navy Yard, Vallejo, California, where entirely new ships were built around the salvaged material and given the wrecked ships’ names and hull numbers.)
Helm: underway to West Loch; damaged by two near-miss bombs; continued patrol; dry-docked 15 January 1942; sailed 20 January 1942.
Shaw: hit by three bombs, causing explosion in forward magazine; returned to service June 1942.
Oglala: minelayer; damaged by shock wave from the torpedo hit on Helena; capsized; returned to service (as engine-repair ship) February 1944.
Vestal: repair ship; hit by two bombs plus blast and fire from Arizona; beached; returned to service August 1942.
Curtiss: seaplane tender; hit by one bomb and shot-down Val; returned to service January 1942; 19 dead.
Sotoyomo: harbour tug; sunk by Shaw’s magazine explosion; salvaged and returned to service August 1942.
YFD-2: yard floating dock; damaged by 250kg bombs; sunk; returned to service 25 January 1942.
Japanese losses were relatively light – 55 airmen and nine submariners were killed in the attack, and one, Kazuo Sakamaki, was captured. Of the 360 aircraft committed, 29 were lost: nine in the first wave (three Zeros, one Val, and five Kates) plus 20 in the second wave (six Zeros and 14 Vals), with another 74 damaged by AA fire.
In December 1941, the US Pacific Fleet comprised nine battleships, three aircraft carriers, 12 heavy cruisers, eight light cruisers, 50 destroyers, 33 submarines, and 100 patrol bombers.
Although the attack effectively destroyed the Fleet’s largely obsolescent battleships, the crucial factor was that none of the three carriers were caught by the attack. At the time, Saratoga was heading for San Diego to embark her air group, which had been training ashore while the ship was refitting.
Enterprise and her task force were returning to Hawaii after delivering Marine fighter squadron VMF-211 to Wake Island. They were due to arrive at Pearl Harbor on 6 December and almost certainly owed their survival to bad weather, which delayed their arrival until the following afternoon.
Task Force 12, comprising Lexington, three heavy cruisers, and five destroyers had left Pearl Harbor on 5 December to ferry 18 US Marine Corps Vought SB2U Vindicator dive-bombers of VMSB-231 to reinforce Midway Island. On the morning of 7 December, the Task Force was about 930km south-east of Midway when it received news of the Japanese attack and was diverted to search for the enemy carriers. (It was fortunate that Lexington failed to find them, as, even after their losses, the IJN’s carriers’ air wings still had a massive superiority and would almost certainly have sunk her.)
The survival of all three US carriers allowed the Pacific Fleet to recover remarkably quickly – as Yamamoto put it in a discussion with the Japanese Prime Minister, Prince Konoe, ‘In the first six to 12 months of a war with the United States and Great Britain, I will run wild and win victory upon victory. But then, if the war continues after that, I have no expectation of success.’ (The IJN’s first decisive defeat at Midway came just six months after the attack on Pearl Harbor.)
Perhaps the final words should be another (apocryphal) Yamamoto remark: ‘I fear that all we have done is to awaken a sleeping giant and fill him with a terrible resolve.’ •
All images: WIPL, unless otherwise stated.