When the Japanese attack force of level, dive, and torpedo bombers pounced upon the American fleet anchored in Pearl Harbor on 7 December 1941, they achieved an overall accuracy rate of 37% - a truly remarkable achievement. In training exercises the Japanese had already topped the levels reached anywhere else. While the level bombers of most other nations hit their targets only 1% to 3% of the time, Japanese pilots preparing for Pearl Harbor were getting hits 14% of the time, from 8,500 feet; in the Pearl Harbor attack, their accuracy rate for direct hits on ships jumped to 43%.
Germany's Stukas achieved 25% accuracy, while Japanese divebombers were hitting practice targets 30% to 34% of the time; at Pearl Harbor, under fire, their accuracy rate was at least 26%. By late 1944 the US Navy was pleased to achieve a 40% accuracy rate for practice torpedo bombing. In training the Japanese torpedoes were hitting 70% to 80% of daylight targets and 50% to 75% at night; at Pearl Harbor their accuracy rate was 51%. After Pearl Harbor, the myth of the tremendously effective Japanese bomber pilot was born - and deservedly so. How had these extraordinary success levels been reached? And could they be sustained, and replicated elsewhere? Did the reality match the myth beyond Pearl Harbor?
Preparation and Problem Solving
Japanese pilots practised bombing from 8,500 feet using steel sheets the same thickness as US battleships' deck armor as targets. From this exercise it was learned that the bomb weight needed to be increased to 800 kg to provide enough kinetic energy to penetrate. There was not time to design and manufacture an 800kg bomb, so the Japanese improvised, welding tail fins onto 16-in. naval gun shells. Then they had to design and build new bomb racks because their older planes had racks which were too small to carry the larger projectiles. These new racks insured that the improvised 800 kg bombs would swing clear of the propeller arc after release. The bombing problem was solved.
Installing the new racks took so long that carriers sailed from Sasebo naval base on the southern Islannd of Kyushu with civilians aboard, feverishly working to complete the modifications. When the task force set sail for Hawaii, the civilians were transferred to a tanker anchored in Hitokappu Bayin the Kurile islands and held incommunicado until after the attack.
The Japanese planners also had to solve serious torpedo problems. If the Americans had torpedo nets in place, the plan was for B5N 'Kate' pilots to carry out suicide attacks to destroy them so others could complete the mission. Although Rear Admiral Husband E. Kimmel, commander of the US Pacific Fleet, requested torpedo netting, the Navy claimed it could not afford to send any. Later when the US Navy court-martialed Kimmel, one of the charges brought against him was failure to have torpedo netting in place.
The second problem was presented by the shallowness of Pearl Harbor. When a torpedo was launched from a bomber, it normally sank to betwen 60 and 75 feet before coming up to its pre-set running depth. Because Pearl Harbor had an average depth of 40 feet, a standard torpedo would embed itself in the muddy bottom. On the night of 11-12 November 1940, the British surprised the world with shallow water torpedoes which sank several Italian warships in Taranto harbor, like Pearl a shallow anchorage. Immediately after the attack, Lt. Cmdr. Takeshi Naito, Assistant Naval Attache in Berlin, flew to Taranto to investigate. He was able to radio Tokyo the secret of the British shallow-water torpedo - wooden fins to add buoyancy.
The Japanese designed their own modification, but only 30 of the torpedoes could be ready by 15 October for practice use. A second batch of 50 torpedoes was to arrive not later than 31 October, and the final 100 modified torpedoes were not scheduled for delivery until 30 November. The fleet was scheduled to sail on 20 November 1941, so it appeared that a portion of the mission was seriously at risk. Yukio Fukuda, who was in charge of the torpedo project at the Mitsubishi factory in Nagasaki, ignored his company's no-overtime policy to force the project through to completion by the required date. Still, time was tight. The carrier IJN Kaga waited behind at Sasebo and took delivery 24 hours after the other carriers had sailed, then moved quickly to rejoin the task force.
Attack on Pearl Harbor
According to the US Navy's Summary of War-Damaged Navy Ships A374 (published 15 September 1943), 20 torpedoes hit American ships. Only the 40 Mitsubishi 'Kate' torpedo bombers of the first wave carried torpedoes. The USS Nevada shot down one 'Kate' before it could release its load, so only thirty-nine torpedoes were dropped. Twenty found their mark, a 51% score for this strike. This was well below the 70%-80% scores of practice runs, but the planes were not being shot at while practising.
In the first wave 21 of the 49 800kg high altitude bombs scored direct hits on the battleships USS Arizona, California, Maryland, Nevada, Pennsylvania, Tennessee and West Virginia; three more damaged the USS Oklahoma with near misses. The Japanese pilots targeting battleships had a 43% accuracy rate, 49% including near misses. In either case, the Nakjima B5N 'Kate's' level bombing was far better than predicted and much better than the 13%-14% achieved before intensive training. Aichi D3A1 'Vals' in the first wave carried 250kg bombs and dive-bombed the airfields.
In the second wave, Lt. Cmdr. Shigakazu Shimazaki led 54 'Kate' level bombers on a mission to attack the four airfields. The attacks on the airfields were highly effective, but the nature of the targets makes it impossible to separate and analyse the damage caused by dive-bombing, level bombing and strafing, and the consequent fires and explosions. 79 Mitsubishi A6M 'Zeros' played an important part in the whole operation, strafing ground targets and providing fighter cover. Lt. Cmdr. Takashiga Egusa led 78 or 80 'Val' dive-bombers with 250kg bombs to attack battleships and cruisers. Accounts and records vary as to the precise number of aircraft. Certainly, Egusa's dive-bombers did very well. They stopped USS Nevada's rush to the sea, sank Pennsylvania and Shaw, and destroyed both Cassin and Downes in dry dock. They also damaged Raleigh, Honolulu, Curtiss, Cummings, and Rigel while scoring near misses on New Orleans. Damage analysis reveals that few ships hit by the first wave received damage from the second.
Of 80 bombs, 21 were effective, a 26% accuracy rate; if Egusa only had 78 bombers, accuracy rises to 27% which is still less than the 30%-34% scored in practice. The difference is readily accounted for by the fact that the pilots were diving into smoke which obscured many targets while evading much more flak than greeted the first wave. The first wave lost one 'Val', five 'Kates', and three Mitsubishi A6M 'Zero' fighters which were escorting the bombers and strafing opportune targets, the second, 14 'Vals' and six 'Zeros'.
1 At 0803 hrs, two torpedo planes attack the Nevada while she is still berthed at the north-east end of Battleship Row. Gunners on board manage to shoot both of the planes down, but one manages to launch a torpedo and scores a direct hit on the port bow, at frame 40. The blast shakes the whole ship, and she begins to take on water. This constitutes the most significant damage done to the Nevada during the whole of the Pearl Harbor attack.
2 0900 hrs: Japanese bombers spot the Nevada as she passes TenTen Pier in her break for safety, and swoop down on her from the south-west and south-east in a split formation (the idea is to confuse and split the American AA fire). Only the planes that attack 'in the sun' manage to score hits with their bombs. The planes, led by Lt. Saburo Makino, target her foreturret and midsection. During this intense period of attack, she sustains three direct hits from Japanese Val dive-bombers in her fore (2A, 2B and 2C). She continues to take on water, but presses ahead.
3 Fire engulfs all the compartments on the second and main decks in the fore of the ship following the direct hits scored in this area. It will continue to burn fiercely for 48 hours.
4 0907 hrs: Lt. Yamada's team of dive-bombers take over the attack and swoop in on the stricken ship. A fourth bomb hits the forecastle, causing considerable damage and costing the lives of several crew members.
5 A fifth bomb hits the Nevada shortly after, at the base of her rear tripod mast.
6 A powder fire has broken out in her gun casemate, to starboard of her rear tripod mast. The Nevada is by now sitting low in the water. Her acting captain realizes she is in danger of blocking the channel by sinking where she is, so the decision is taken to beach her on the near-by Hospital Point. The time is just after 0910 hrs.
Attack On Force Z
Three days after Pearl Harbor on 10 December, Japanese torpedo and
high level bombers flying from Saigon across the South China Sea engaged the British Navy's Force Z off the east coast of Malaya and sank the battleship HMS Prince of Wales and the battlecruiser HMS Repulse.
Near midnight of 9-10 December 1941, Lt. Cmdr. Sohichi Kitamura's submarine I-58 located Force Z 100 miles off the east coast of Malaya. He could not immediately engage because a torpedo jammed in one of his tubes. After the jam was cleared, he fired a spread of five torpedoes which missed because the ships were now too distant. Kitamura then reported the force to Admiral Nobutake Kondo who ordered the three bomber kokutais (air groups) of his 22nd Air Flotilla into action. Unlike the targets at Pearl Harbor, these ships were fully alert and ready to fight back, sailing at full speed with destroyer escorts.
10 December, 0625-0800 hours: 31 level bombers and 51 torpedo bombers took off from Saigon 1045: nine G3M 'Nell' level attacked the destroyer HMS Tenedos which had run short of fuel and was returning to Singapore. They missed.
1113: eight 'Nell' level bombers commanded by Lt. Yoshimi Shirai scored a direct hit and two straddles on Repulse with 250kg bombs from 11,500 feet. Five suffered AA damage and two were badly hit, returning immediately to Saigon.
1144: Lt. Kaoru Ishihara attacked Prince
of Wales with nine 'Nell' torpedo bombers. Two torpedoes hit their mark but AA fire destroyed one bomber and damaged three others.
1158: Lt. Takai led his torpedo bombers against Repulse. Four of the eight planes were damaged by AA fire. Taki's torpedo failed to release, and all the others missed. Takai made a second solo attack but also missed.
A few minutes later, Lt. Shirai led his six remaining 'Nells' on a second bombing run against Repulse. Braving fierce AA fire, they dropped their last 250kg bombs from 12,000 feet and missed.
1205: Within minutes, seven 'Bettys' made torpedo attacks on Repulse. All missed.
1220: 6 Mitsubishi G4M 'Bettys' armed with torpedoes struck at Prince of Wales and four of the first six torpedoes launched hit. 17 'Bettys' then turned on Repulse, attacking from all directions. Three torpedoes scored hits while two of the attacking aircraft were downed by AA fire. Eight aircraft suffered heavy damage, and one later crashed while trying to land at Saigon
1232: A final torpedo struck Repulse's propeller shaft and she sank.
1246: 17 'Bettys' attacked Prince of Wales from 8,500 feet. All 9 of the 3rd Hikotai's bombs missed. Lt. Hachiro Takeda's 2nd Hikotai dropped 8 more bombs and scored one hit.
1318: Prince of Wales sank.
Only two out of the 40 bombs dropped actually hit their targets, giving the Japanese level bombers a 5% accuracy rate. Counting near-misses, their accuracy improves to 10%. Ten out of 51 torpedoes found their mark, giving a 20% accuracy rate.
Attack on Doorman's Task Force
On 15 February 1942 the Dutch Rear Admiral Karel W.F.M. Doorman was off Java in command of a 15-ship Allied task force in the Dutch East Indies consisting of the cruisers HNM De Ruyter, Java, and Tromp, HMS Exeter and HMAS Hobart, and four Dutch and six American destroyers. Under cover of darkness Doorman was approaching Bangka Strait at the south-eastern end of Sumatra where he hoped to intercept 26 Japanese transport. Doorman aimed to sink the transports before they could disgorge their invasion troops to advance on Palembang.15 February, 0800 hours: A floatplane from the cruiser IJN Chokai spotted Doorman's force.
0805: The carrier IJN Ryuho launched seven 'Kates'.
1030: Ryuho's 'Kates' made a high-altitude bombing run and missed.
1100: 23 'Nells' arrived from their base at Kuching in northern Borneo to deliver an equally ineffective high altitude bombing attack.
1200: Admiral Doorman's fleet had closed to within 80 miles, so Ozawa scattered his transports and ordered his escorting warships into battle formation. Doorman ordered his force to make for Tanjong Priok in Java to take them out of the range of land-based bombers. As they withdrew, 27 'Bettys' from Kuantan, Malaya delivered another ineffective high-level bombing strike
1300: Six more 'Kates' from Ryuho delivered another ineffective attack.
1430: Seven 'Kates' from Ryuho returned but failed to inflict any serious damage with high-level bombing.
1630: Six 'Kates' from Ryuho methodically repeated the failure.
Dusk: 17 'Bettys' found Doorman's ships after a five hour flight from their base in Saigon. Like earlier attacks, this one inflicted virtually no damage.
Although 93 Japanese bomber sorties were made in daylight and met no fighter opposition, damage to Doorman's force was minimal. The destroyers USS Blumer and Baker reported light damage from near misses, and HMS Exeter had only some splinter holes. Doorman would sail on to defeat and death at the Battle of Java Sea on 27 February, when his flagship De Ruyter and the Java were sunk by torpedoes from Japanese destroyers and cruisers.
By this date the Allies had developed two effective counter-measures. First, the whole force paid close attention to every approaching enemy aircraft so that the target ship would be protected by AA fire from all ships within range as well as her own. Second, ships made violent course changes as soon as bombs were released to avoid direct hits. (At Midway in June 1942 the Japanese used the same tactic to avoid damage from B-17 bombers.)
There may have been additional reasons for this lack of success. The 'Kate' was designed to carry a bomb or a torpedo. Because level bombing had a lower success rate, it would have made better tactical sense for Ryuho's 'Kates' to carry torpedoes. However Ryuho's pilots had apparently not yet been trained in torpedo attack procedures and her torpedoes were poorly maintained. Weather was another factor. The 'Nell' and the 'Betty' were also designed to carry either bombs or torpedoes. But heavy rains had left Japanese airfields too soggy to support the weight of a bomber carrying a torpedo or its full load of two bombs. The land-based bombers attacking Doorman's fleet therefore carried only one bomb because they became bogged down on the runway and could not take off carrying a heavier load.
From Myth to Reality
The statistics of the Z Force action three days after Pearl Harbor and of the attack on Admiral Doorman's task force two months into the war graphically illustrate a downward trend from the accuracy rate achieved at Pearl Harbor. This can also be seen by comparing the accuracy rates achieved, and losses suffered, by the first and second attack waves on 7 December 1941. From Midway, 4 June 1942 onwards overall performance was much lower, between 7%-10% according to some sources.
The Japanese were outstandingly effective at Pearl Harbor but there they were able to open their attack in ideal, target-practice conditions against an almost totally unprepared enemy. Their intensive training and preparation had been focused on this specific mission. And they had the benefit of excellent intelligence gathered from an enemy that was not yet on a war-footing. Z Force and Doorman's task force were moving targets, defended with fierce anti-aircraft fire from the start. As the war continued and Allied tactics improved - especially the use of air cover, which was not available to Z Force and Doorman - attrition severely weakened the Japanese. Experienced and properly trained pilots were replaced with young, less thoroughly trained recruits. Pearl Harbor indeed proved to be the extraordinary exception, not the rule.
About the Author:
Louis Zocchi is a writer, and designer of Luftwaffe and Battle of Britain games. He is an authority on aircraft and air warfare when not on active duty with the US Air Force.
Related Reading:
Boatner, M. A. The Biographical Dictionary of World War II (Presidio Press, 1996)
Boyne, W. J. Clash of Titans: World War II at Sea (Simon & Schuster, 1997)
Prange, G. W., Goldstein, D. M. & Dillon, K. V. At Dawn We Slept: The Untold Story of Pearl Harbor (Viking Penguin, 1982)
Smith, C. Campaign 62: Pearl Harbor 1941 (Osprey, 1999)
Sakaida, H. Aircraft of the Aces 13: Japanese Army Air Force Aces 1937-45 (Osprey, 1997)
Sakaida, H. Aircraft of the Aces 22: Imperial Japanese Navy Aces 1937-45 (Osprey, 1998)
Tagaya, O. Warrior 55: Imperial Japanese Naval Aviator 1937-45 (Osprey, 2003)
Williford, G. & McGovern, T. Fortress 8: Defenses of Pearl Harbor and Oahu 1907-50 (Osprey, 2003)