by Attack on Pearl Harbor: Strategy, Combat, Myths, Deceptions
Hits on ships in the yard could be particularly devastating. When undergoing what is known as “shipyard availability,” material condition Zed cannot be set. Electrical power cables, welding leads, and high and low pressure air hoses are strung through watertight hatches from their sources on the pier down into the depths of the ship, making it impossible to close hatches to contain either flooding or fire. One cruiser had a large access port cut into her side to remove machinery. Portions of a ship’s firemain system might be isolated and drained for valve maintenance. Lots of flammable materials—oils, grease, oil-based paints, wooden staging—would be scattered throughout the ship, a damage control nightmare.
A bomb hit on a ship in this condition could cause fires and flooding that could not be isolated, and could potentially spread progressively throughout the ship. A bomb hit could be expected to cause much more damage than under normal combat conditions. This should have been recognized by the Japanese before the attack. These were lucrative targets in a very vulnerable condition.
The Chronology estimated that 30 dive-bombers attacked the Navy Yard area (including those that attacked Pennsylvania). These attacks were inaccurate. Only two hits were achieved, one each on Honolulu and Pennsylvania. Most made thundering splashes that almost swamped yard craft. One bomb did shatter a ship’s boat, wounding three men with bomb fragments.
The dive-bomber pilots were instructed to dive into the wind, in order to better maintain their dive angle and so the wind would not push their bomb off line. To make this approach, they had to pass close to the cloud of smoke billowing out of Battleship Row up to an altitude of 8,000 feet, a column of turbulence that without doubt disturbed their attempts to get lined up on their targets during the critical initial part of their dive. Some of the pilots ignored this instruction, as American observers noted dive-bombers coming in from both the west and the east.
The story could have had a happier outcome for the Japanese had they followed their target prioritization scheme and hit the cruisers in the Navy Yard with more bombers more accurately. In the first year of the war, with many of the battleships knocked out and with insufficient tankers to keep the remainder in fuel in forward areas, cruisers became the “heavy units” of the surface war in the Pacific, and were constantly in demand and short in supply. By employing dive-bombers against battleships, more of these critical cruisers survived. The bombers diverted by Egusa to the more spectacular, but less logical and less appropriate battleship target, could have had a greater impact on the war than they did.
Striking Nevada was an emotional, Japanese-logic decision that backfired. It provided the most memorable inspirational event that cheered the defenders on, rather than another nail in their intended coffin of despair.
Blocking the Channel by Other Means
Had the planners really wanted to sink a ship in the channel, there was Neosho, one of the largest tankers in the world. Neosho pulled out of her mooring at the Ford Island Fuel Pier just after Nevada passed by. She was 50% to 75% full of volatile aviation fuel. She would have been easier to put on the bottom than Nevada, but even then it would have been no easy thing, with her large tanks holding a cargo that was lighter than water. At the Battle of the Coral Sea, Neosho was hit by seven bombs and one suicide aircraft and at one point was abandoned due to fires, yet remained afloat for four days.
Photographs show Neosho in the channel and lining up to enter the Southeast Loch past the Navy Yard as the dive-bomber attacks began. If the Japanese wanted to sink a ship in the channel, Neosho was the better choice. But, even against her, more than 14 bombers would be needed.
Two dive bomber pilots made an attempt. Neosho’s AR reported that “several bombs fell close to the stern jarring the ship appreciably.” Otherwise, Neosho’s crew was more than pleased to be ignored.
The most appropriate method to block the channel would have been with mines. Considering that cruisers Phoenix and St. Louis and several destroyers sortied in spite of reports that there were mines in the channel, the chances were high that a well placed mine would score before any minesweeping effort could be organized. However, aerial mining was not in the Japanese mindset. The Japanese considered mines to be defensive weapons. They did not have an effective air-delivered mine until the Type 3 was developed in 1943.
Overall, the Japanese second-wave dive-bombers expended 18 weapons (14 against Nevada, and two against Dale while she was steaming out of the harbor in the channel, and two against Neosho), nearly 1/4th of their available bombs, in attempts to block the channel. Five additional weapons were expended against the destroyers Dale and Helm when they were beyond the channel and outside the entrance buoy—evidently five of the dive-bomber pilots found the AA fire in the harbor too hot for their taste. Twenty-one of the available 78 weapons were wasted on inappropriate targets.
Dive-Bomber Targeting
Gauged against the objectives of the attack, none of the dive-bombers’ attacks directed against battleships accomplished anything significant. They put a hit and a near miss on Pennsylvania in drydock, which did not affect the ship’s long-term combat readiness, and put five hits on a battleship that was already out of the war for at least six months due to a torpedo hit. They seriously damaged three destroyers (two probably by accident, with bombs likely aimed at battleships). Other dive-bombers hit a seaplane tender (misidentified as a cruiser) that required four days in the shipyard at San Diego to mend.
Many of the dive-bombers misidentified destroyer tenders as cruisers. The Imperial Navy did not employ destroyer tenders as did the Americans. Instead, they assigned their 5,200-ton light cruisers (such as their Kuma and Nagara-class ships) to serve as flotilla leaders, and Japanese destroyers normally nested with them. Attacking a nest of destroyers, the aviators reported what their experience told them was a cruiser nested with destroyers.
A few dive-bombers that somehow found themselves miles south of the objective attacked the destroyer Helm south of the entrance channel buoy. Two near misses flooded her forward peak tank and put severe cracks into the fire control tube supporting the massive Mk 37 main director. A few weeks later a marine railway hauled Helm out of the water. Temporary repairs were made to the bow, and the fire control tube was re-welded. Permanent repairs were performed seven months later in drydock at Sydney, Australia.41
Ineffective attacks were scattered about. In all, five dive-bombers went after destroyers that were underway departing the harbor (misidentified as cruisers), two went against a destroyer outside the harbor (misidentified as a cruiser), several bombers went after tenders on the west side of Ford Island, and one attacked an ammunition ship pierside in the West Loch. There was even a report of bombs dropped on the armed Dutch liner Jagersfontein off Honolulu, an attack that the Dutch reportedly resisted with spirited AA fire.42
The full distribution of attacks will be analyzed in the next chapter, but it is enough to observe that about one third of the dive-bombers attacked targets at the bottom of the priority list when higher priority targets were undamaged.
One bomb did wonders for some American sailors’ morale. It blasted open a mobile Gedunk Wagon43 on 1010 Dock. Men from the Helena and everywhere within shouting distance raced to gather pies, ice cream and candy bars, their fast reaction ensuring that the Japanese could not claim credit for the destruction of vital supplies.
250kg Bomb Malfunctions
Many of the 250kg GP bombs malfunctioned. Some, such as a bomb that landed off Pennsylvania’s bow, caused so little damage that they might have been low-order detonations. Two which landed ahead and behind Rigel at the Navy Yard piers were duds. Another four duds were reported by Avocet south of Ford Island as she observed the attacks on Nevada. Cachalot reported a dud bomb that landed 20 feet off her starboard quarter, possibly one directed at Neosho during her transit to Merry Point.
Of eleven GP bombs that hit Ford Island, two were duds and one a low-order detonation which scattered a “yellow sulfuric powder” that caused skin burns.44 The
se eleven bombs exhibited a 27% malfunction rate.
Some of the reported duds that landed in the water could have been splashes caused by AA shells. The reports listed above correlate to divebombing attacks and were likely accurately identified as bombs. It is also likely that there were other duds or low-order detonations that went unrecorded.
The 0.2 second delay fuze, appropriate for finishing off carriers, was less effective against smaller ships. Many bombs that missed buried themselves in the bottom of the harbor before exploding, delivering up only a torrent of mud. Bombs passed entirely through Nevada and California to explode in the water. Yet, many bombs also exploded on the surface inflicting fragmentation damage, indicating that the fuze delay function was inconsistent.
Bombs reported as “incendiaries” were weapons with quality control problems. Poor detonation could occur if the explosive filler was loaded haphazardly with air gaps and irregularities, so that some of the explosive underwent a prolonged low-order partial detonation or deflagration that would spread dramatically colored burning fragments. This could give the red signature mentioned in the reports.45
The 250kg GP bombs with their long delay fuzes were also inefficient against ground targets. One of these weapons hit in the Ford Island dispensary courtyard. The resulting crater was about 10 feet deep with a diameter of 25 feet. The bomb did little beyond that. All the force of the explosion was spent in digging the crater and blasting the debris almost straight up: the walls of the dispensary, some directly adjacent to the crater, were hardly damaged, with only a few scratches and score marks; some windows at the lip of the crater retained some of their glass.
As in the case of the 800kg AP bombs, the 250kg GP bombs were deficient. The Japanese aviators were let down by their ordnance establishment, twice over.
Dive-Bombers’ Attack: Summary
Overall, the dive-bombers’ most significant contributions towards achieving the objective of the attack were a hit on the cruiser Raleigh and a DNM on Honolulu. The bomb hit on Raleigh, along with a torpedo hit amidships, almost capsized the ship. After drydocking she was seaworthy enough to escort a convoy to the West Coast in February 1942. The hits kept her out of the war for eight months. The DNM on Honolulu dished in her hull about five or six feet over a 40-foot length, causing flooding. She was put to rights before the end of December and was out of the war less than a month.
By a combination of bad decisions, bad bombing, and bad ordnance, the 78 dive bombers in the second wave made no substantive contributions to the attack.
Assessment: Fighter and OCA Performance
Fighter Doctrine
The Japanese considered fighters to be an offensive strike asset. They were to engage enemy fighters in the air or strafe aircraft on the ground. They were not given formal responsibility for the safety of the bombers. This was a philosophical orientation that both limited the fighters’ accomplishments and made their OCA (offensive counter-air) effort a huge success.
The planners did not assign fighters as top cover. When the approach to the target was made the entire fighter force shifted to the attack, going after either aircraft in the air or aircraft on the ground. They were not responsible for the safety of the bombers with which they flew. Most became “target fixated” in their ground attacks and lost situational awareness, so much so that several US fighters were ignored until they started shooting down bombers.
With only 45 fighters in the first wave and 36 in the second wave over a 600-square-mile island, it ought to have been expected that some enemy aircraft could get aloft even if complete surprise was achieved. Second Lieutenants Welsh and Taylor took off from Haleiwa Airfield and were vectored to intercept aircraft strafing Ewa Airfield. They hooked on to the tail of a long line of aircraft and scored two confirmed kills apiece.46 Other US fighters reported a similar situation. Most of the US kills were against Japanese planes that did not see them.
This is not unexpected: after the Vietnam War, several US Air Force studies (most notably, the Red Baron study) found that 80% of the pilots killed did not know they were being targeted until their attacker opened fire. This is just what happened over Pearl Harbor, and exactly what top cover aircraft were supposed to prevent.
Japanese fighters were never particularly effective as escorts. During the war in China:
…one of the real problems of fighter tactics was the tradition of personal combat that went back to Japan’s middle ages. In aerial warfare, this tradition was manifested in the Japanese penchant for dogfighting. It was difficult for Japanese navy pilots to forgo the opportunity for personal glory in the individual dogfight for the sake of the teamwork demanded by formation flying…. There were other reasons for the failure of Japanese close fighter support for bomber formations, of course. One was the lack of oxygen equipment in the A5M fighters. Even more critical was the absence of adequate aircraft-to-aircraft communication.47
The war in China forced Japanese naval fighter pilots to reconsider their role in escorting bombers, as unescorted bombers were taking horrendous losses. Any resulting change in mindset was lost after the Japanese naval participation in long-range bombing missions was withdrawn. Formation flying and group tactics came to be ignored, and naval fighter pilots “reverted to their predilection for the individual heroics of dogfighting.”48
The Japanese Operations Order assigned specific groups of fighters to attack specific airfields, but not to provide persistent top cover. Even then, the fighters often ignored their geographic assignments. Many Japanese fighters, after hitting the obvious targets at their assigned location, flew off looking to expend the rest of their ammunition in more exotic locales. Not being held down by top cover, a few US fighters did manage to get into the fight. US Naval War College figures estimated that fighters attacking bombers would shoot down four bombers for every ten fighter sorties. At Pearl Harbor, the US fighters shot down eight to 11 aircraft in 14 sorties, or 1.5 to 2 times the predicted rate.
The lack of provision for top cover was a by-product of the Japanese single-minded concentration on offensive action at all costs. At one time in the mid-1930’s, the Japanese seriously considered giving over carrier flight decks entirely to bombers. “When Lt. Comdr. Shibata Takeo, a leading fighter pilot, tried to point out to a Navy General Staff officer the importance of fighters in defending the fleet, the latter shot back a stinging rebuke against defensive tactics: ‘And you claim to be a Japanese!’”49
Attackers tend to become fixated on their target, excluding from their attention peripheral vision, sounds, or other considerations. Defending bombers requires wide area situational awareness, with the pilots’ “head on a swivel” instead of watching the fireworks. It takes a great deal of discipline to stay with the bombers and not hare off chasing individual glory. Unless fighters are specifically designated to stay and defend the bombers, aggressive fighter pilots will go roving, leaving behind gaps for enemy fighters to exploit.
Comparative Attrition
It could be argued that the loss of 8 to 11 bombers was small compared to the damage that the strafing fighters caused. However, it is not known what the Japanese expected from their strafing fighters. A thumb rule used by analysts is to expect between 2.5 to 5 aircraft destroyed on the ground for every 10 fighters employed in airfield strafing missions. With 45 fighters assigned to strafing in the first wave, this would give an expectation of 11 to 23 aircraft destroyed. Combined with the expectations from the dive-bombing attacks, this would give a Japanese expectation of destroying 47 to 77 aircraft on the ground in a surprise attack. This calculation is on the same order of magnitude as the results in one of the Japanese wargames, where they expected 80 aircraft to be destroyed on the ground (albeit with a smaller number of carriers in the attack).
The performance of the fighters in their strafing mission is hard to evaluate. American aircraft were destroyed on the ground by D3A Val dive-bombers, and some Vals also strafed the airfields. It is impossible to determine how many US aircraft were destr
oyed by bombs, how many by strafing, and how many by being caught in gasoline fires while crowded together in their “anti-sabotage” parking arrangement. Instead of strafing individual aircraft the Americans’ parking scheme transformed difficult “point” targets to easier “area” targets. Planes were so crowded together that nearly every machine gun bullet and ricochet caused damage.
In areas where the aircraft were not parked wingtip-to-wingtip the fighters performed less well. For example, the fighters that attacked Kaneohe likely put in only an average performance. Movie film taken by a second wave B5N Kate level bomber shows seven seaplanes parked near the hangars, only two of which appear to have been damaged by the first wave fighters.50 After the second wave bombers departed, of the 33 PBY’s on the ground and floating offshore, 27 were destroyed and six damaged.51
Prior to the actual attack, the Army Air Corps had 143 operational aircraft on Oahu, with an additional 88 under repair, a total of 231 aircraft. After the attack there were 87 operational USAAF aircraft, 79 repairable or under repair, and 65 destroyed, for a net loss of 56 operational aircraft and 9 aircraft under repair, a net change in status of 65 aircraft. Of the 301 US Navy aircraft, before the attack 202 were operational, 52 in storage, 31 in overhaul, and 16 under repair. Of these aircraft, 80 were destroyed and 169 damaged, a net change in status of 249 aircraft. This totaled 314 aircraft hit by 189 aircraft allocated to OCA, or a return of 1.66 aircraft destroyed per aircraft committed, three to six times higher than the historical rate of .25 to .50 aircraft per sortie. The primary factors were the lack of air opposition and the fact that the American aircraft were not dispersed and not in revetments.