by Attack on Pearl Harbor: Strategy, Combat, Myths, Deceptions
The aviators of the Kido Butai, the carriers of the Mobile Striking Force, averaged 800 hours at the time of Pearl Harbor. To place this in context, Japanese pilots received about 300 hours in basic training and 200 hours in advanced training before being assigned to a carrier. This took about two years, a year of ground school followed by a year of flight training. Even then, a pilot reporting to an aircraft carrier was not an “all-up round” ready for combat. Peattie found that “Japanese naval aviation, unlike the other branches of the service, mainly used its operational units as training facilities rather than training its personnel in specialized schools.”5 Aviators newly assigned to an operational carrier needed to qualify in their front-line aircraft, learn to land on a carrier, fly in formation, launch and marshal, and fight.
A “large-scale reshuffling” of the air groups occurred in early September 1941,6 two months before the departure of the ships for the Pearl Harbor operation. Large numbers of junior aviators were introduced into the air groups. Among the critical torpedo bomber aircrews, many young, green fliers were initially assigned to the carrier groups from August throughout September. It was four to six weeks before the new arrivals completed their basic carrier qualifications.7 This turnover was normal, similar to the spate of transfers and promotions that any large military organization goes through as senior people are transferred to training or administrative or command jobs, replaced by new junior personnel. In the memory of one Japanese aviator, “Usually people spent only one year on a carrier, because it was physically exhausting.”8
As a result:
Owing to comparatively large-scale reshuffling before the operation, there had been many fliers who were not familiar with landing-on-carriers practice. Moreover, efforts had to be made to have carriers available for that practice, for during that period carriers were engaged in one-by-one repairing.
Most of the training time for young fliers was therefore used in landing-on-carriers practice which was the fundamental technique.9
In September 1942 there were many new pilots (“nuggets” in modern US Navy slang) fresh to the Japanese carriers. There were also new ships to be manned, as escort carrier Kasuga Maru joined in September and fleet carriers Zuikaku and Shokaku were completed in October of 1941. This added an additional capacity of 171 carrier aircraft, up from 351, or a one-third increase.10
Ensign Honma Hideo, a B5N Kate pilot assigned to Zuikaku, relates:
Frankly speaking, I feel that many of the aviators on the carriers Zuikaku and Shokaku were really “green” and had very little flying experience. For example, only three pilots (including myself) had experience doing torpedo attacks using a Type 97 [B5N Kate] carrier attack plane. So, compared to the aviators on our other carriers, most of our men were not that experienced as pilots. Hence, prior to Pearl Harbor, we did mostly basic flying maneuvers, such as take-offs, landings, and a little bit of formation flying. We also did some level bombing training with our Type 97s…. most of the men on our carrier were “rookie” pilots…11
Ensign Honma was 19 years old and one of the more experienced aviators on his ship. The two others in his crew were 16 or 17 years old. The aged Honma “felt they were still kids.”
Genda, in a postwar analysis of the Pearl Harbor attack, admits that the “airplane units of the 5th Carrier Division [new carriers Zuikaku and Shokaku] could not keep up with the 1st and 2nd even to the end because the units were newly organized and were not trained sufficiently.”12
One Japanese senior officer mentioned that when these ships joined the fleet skilled A6M Zero pilots were hard to find. Airmen were transferred from the light carriers Ryuji and Shoho,13 while others were pulled from instructor duty and experimentation duty with the Yokosuka Air Group.14 This provoked opposition from the Navy Ministry’s Aeronautical Department and the Personnel Bureau. Yamamoto was risking his “seed corn;” if these experienced aircrew were lost, the lack of trained and experienced instructors would make it all the more difficult to reconstitute the air groups.
The converted former luxury liner Kasuga Maru joined the fleet as an escort carrier [later named Taiyo] three months before the Pearl Harbor attack. She was fitted for an aircraft complement of 27—nine A6M Zero fighters (with 2 spares) and 15 B5N Kate carrier attack bombers (with one spare). However, there were insufficient airmen to make up her air group,15 and so she was classified as an auxiliary and relegated to duties as an aircraft ferry. She was reclassified as a warship on 31 August 1942, but performed ferrying duties for a considerable period thereafter, only participating in one operation in a combat role.
All the aircrews began an intensive period of training for the attack. For the B5N Kate carrier attack bombers assigned to carry torpedoes, it meant three sorties a day for many weeks. For the dive-bombers, Abe Zenji, commander of a group of nine dive-bombers on carrier Akagi, testified, “These practice missions continued over and over, on some occasions for five hours or more.” According to the Japanese Navy’s post-operation study, “… there had been many fliers who were not familiar with landing-on-carriers practice…. Most of the training time for young fliers was therefore used in landing-on-carriers practice.”16 Abe recalled that among the dive-bombers, “Accidents were common and some aircraft dived into the sea because the pilots were unable to withstand the G stresses in the face of the exhaustion brought on by the severe training schedule… we faced death every day.”17
In other words, a large portion of the air groups were nuggets, and much of their training was devoted to fundamental flying skills. Weapon delivery practice came next. Integrated air group training, or rehearsals of the actual attack, was last, and never satisfactorily accomplished. There was no inter-type training, so the bombers never learned how to work with the fighters, and vice versa. This reflected the Japanese’s “stove-pipe” attitude towards aircraft missions. Each type was independent with little cooperation envisioned.
Under intensive training the aviators would accumulate over 100 hours of flight time per month—Ensign Maeda Takeshi’s flight log recorded 128 hours in October. This would have brought nuggets right out of flight school up to 700 to 800 hours total by November 1941. The sprinkling of second tour aircrew and leaders, most with over 1,500 hours, would bring the average flight hours up to the stated 800 hours average. So, the intimation by some historians that the Japanese aviators having an average of 800 hours denoted an unusually experienced and well-trained force is not correct. The statements in many histories intimating that the Japanese sent to Pearl Harbor a flock of super-pilots, seasoned veterans of the war in China, is a myth. This was a normal contingent of aviators, the majority in their first tour on a carrier. The major advantage was in the 26 flight leaders, of which a few had seen limited action—most of the naval aviators that saw action in China were land-based medium bomber aircrews, not carrier aviators. Only a few strikes, numbering in the single digits, were launched from carriers. The idea that “many” of the Japanese aviators had “hundreds of hours of combat experience” is wrong.
American pilots during the interwar period were given 500 hours before being sent to their squadron for advanced training. Just before the war began, to accommodate the rapid expansion of the fleet, training hours were cut back. Some pilots joined combat units with only 250 hours. They began arriving in the fleet in the autumn of 1942, well after Pearl Harbor.
“The [US] pilots in the service before World War II were an ‘elite’ group,” according to a pilot who joined his first squadron in September of 1942.18 The Japanese training program, in terms of flight hours, was not superior to that given to American pilots during the interwar years. In contrast, in 1939 Canadian recruits were given 100 hours of flight training before receiving their wings and being transferred to combat duty in Britain.19
The Japanese sent to Pearl Harbor airmen trained to typical interwar standards. Their primary advantage over their American opponents was a period of intensive training just prior to the operation, which got the newer airmen (in
cluding most of the aircrew on the two newly-commissioned carriers) up to the same operational level as new American pilots that were sent to operational units. The Japanese aviators that attacked Pearl Harbor were not the super-pilots that folklore would have us believe, particularly the A6M Zero fighter pilots, the subjects of particular veneration in the popular mind. Understanding this, it is easier to comprehend how the American fighter pilots at Pearl Harbor were able to rack up a kill ratio of between four: one to six: one, and lose only 15% of their numbers. When it came to their primary mission, to sweep the skies of American fighter opposition, the Japanese fighters failed. They shot down two fighters that were barely aloft after their takeoff run, but of the fourteen fighters that attained combat altitude they only disposed of two, a far cry from the Japanese fighter performances in China where the A6M Zero would typically shoot down 20 of 23 Chinese fighters. The Japanese fighter pilots were not as good as in China, and the American fighter pilots and their fighters outclassed what the Japanese had previously seen.
The quality of Kido Butai’s fighter pilots would improve over the first six months of 1942, where they had the opportunity to gain more flying hours in attacks that were almost unopposed. They reached peak efficiency during the raid into the Indian Ocean and the attack on Darwin. Even so, they were not overwhelmingly dominant in the Battle of the Coral Sea, and their lack of flight disciple and command and control deficiencies directly led to the annihilation of the carrier striking force at Midway.
The Japanese training standards eroded dramatically during the war. The aviators at Pearl Harbor were much better than later flight school graduates, another contrast that accentuated their relative prowess.
A noteworthy point was that the Japanese planners decided upon the number of bombers to carry torpedoes before they resolved the technical problems of launching torpedoes in shallow waters, and before any reasonable percentage of hits could be estimated. The number of B5N Kate bombers allocated to level bombing attacks against the battleline was also determined in advance, when level bombing percentages were so abysmal that Genda had “almost given up on horizontal bombing.”20
An alternate approach would have been to train all of the aircrews in both forms of attack, and then allocate weapons after the technical issues had been resolved and after a better estimate of hits with each weapon could be determined. This would have allowed the planners the flexibility to change weapon-target pairings at the last minute based on such factors as the accuracy displayed in training or the latest information on the composition of the American fleet in harbor. Instead, the weapons-target pairings and aircraft assignments were made months in advance, and not changed. One reason for this was the training required to get the aviators sufficiently skilled in just one form of attack. They were not sufficiently skilled to swap from one role to another. This limited the flexibility of the planners.
Shokaku and Zuikaku were operational just weeks before the Pearl Harbor raid. Zuikaku and Shokaku’s B5N Kates were all allocated to level bombing attacks against airfields, targets demanding less accuracy than fleet targets.
In the end, the attack time was postponed from dawn to 0800 because a dawn attack would require launching in the dark, and Zuikaku and Shokaku’s air groups were not qualified for night operations. X Day was delayed from 20 November to 7 December because the skill level of the aviators was judged to be insufficient, and more training was needed.21 Ironically, this served to their advantage: if the attack had gone down on 20 November the Americans would have been in Alert 2, with dawn patrols aloft, AA batteries in place, and the Japanese would have suffered.
2) “Thank goodness the fleet was in port…”
Attacking the Fleet Outside the Harbor
Some commentators believed it was fortunate that the US Pacific Fleet was in port, because if it had been attacked at sea, the defeat would have been much more serious. Ships sunk in deep water would have been unsalvageable.
In a scenario supporting this theme, Japan does not attack Pearl Harbor; instead the Pacific Fleet sallies forth to the immediate relief of the Philippines. It is destroyed in deep water by Japanese long-range torpedo bombers operating off island bases. Not only are the battleships all lost in deep water but so are their crews, decimating the experienced Regular Navy talent foundation that served as the cadre for a mass of new construction ships and delivered training to the masses of wartime volunteers and draftees.
While this discussion will explicitly analyze the first scenario, the second can be considered as a lesser and included case.
The “Fleet at sea off Pearl” scenario was tested in a wargame conducted under the auspices of a television program, featuring some of the luminaries of the wargaming world and with the combat results adjudicated by a “sophisticated computer program.”22 In the scenario the US fleet received warning of the attack at 0530, allowing sufficient time for the US commander to sortie the majority of the fleet and meet the air attack while underway in deep water, with the ability to maneuver at full speed, GQ and Zed set, and all AA batteries ready. The results were dramatically announced: four American battleships sunk in exchange for 75 Japanese aircraft shot down.
One of the participants in the game, a retired Rear Admiral, stated that he did not believe these results. He felt that the Americans suffered far too many losses in the game. A careful assessment would suggest that he is correct.
To sink four battleships at sea would have required a minimum of sixteen hits, or 40% of the available torpedoes, very close to the 48% hits the Japanese achieved against stationary targets in a surprise attack. At sea, ships would have been able to maneuver freely, and torpedo hits would have been harder to achieve. Over the last months the US Fleet had been training hard and sailing as if under wartime conditions, and their training and readiness was considered to be excellent. Material Condition Zed would have been set, so the progressive flooding that was so damaging to ships moored in Pearl Harbor under holiday routine would not have occurred as readily.
Compare this situation with that of the attack on the Prince of Wales and Repulse. There, 51 torpedo bombers took off on the mission and 49 torpedoes were launched achieving 6 to 8 hits, or a hit percentage of 12 to 16%.
In that engagement, the two battleships were escorted by destroyers with no area air defense capability. Most of the AA capability was vested in the Prince of Wales. A single devastating torpedo hit, the first to hit the ship, disabled most of the Prince of Wales’ AA capability. A torpedo exploded on the port side aft; it dislocated a port shaft, which thrashed about in the shaft alley smashing the surrounding bulkheads and destroying the watertight integrity of compartments all the way from aft to amidships. Several major engineering spaces flooded, some so fast that the crews could not shut watertight hatches behind them as they evacuated, causing the flooding to spread further. There was a loss of electrical power aft, and the ship took on an immediate 11 degree list, enough so that the 5.25-in AA guns on the high side could not depress sufficiently to engage torpedo bombers. Not one of the eight 5.25-inch gun turrets could be trained due to a loss of electrical power. The six mounts of 8-barrel 2-pounder pom-poms had problems with their ammunition, causing the guns to jam. Stoppages were frequent; one of Prince of Wales’ pom-poms suffered 12 failures, another eight. With power lost all the pom-poms aft were frozen. Sailors tried to train them manually, without success, and in one case they even tried rigging a chain pulley for additional leverage.
With Prince of Wales’ AA weapons largely out of action, Repulse had little to contribute to the defense. She was a WWI vintage ship with only eight hand-operated 4-inch AA and two pom-pom mounts.23
And yet, against this anemic AA opposition, the Japanese achieved only 12–16% hits.
A torpedo hit percentage of 15% underway (the historical average during the war in the Pacific) against the fleet off Pearl Harbor would have given six hits out of the 40 torpedo-armed B5N Kate carrier attack bombers. Battleships at sea could be expected to susta
in at least four aerial torpedo hits without sinking. So, six hits might have (if concentrated) sunk one battleship; if distributed over several ships, all ought to survive.
Similarly, the hit percentage by 800kg bombs would be reduced from that achieved against the stationary ships on Battleship Row. Hits by level bombers against maneuvering targets were notoriously hard to achieve during all of WWII. A 10% hit rate (5 hits) would have been exceptional, higher than the hit percentage exhibited over the entire war, which was probably less than 1%.24 Five hits (with a 60% dud or reduced yield rate) would not have done serious damage to the battleline as a whole.
American AA was considerably advanced over the British. The 40 torpedo bombers would have received considerably more attention than that offered by the British battleship and battlecruiser. An apt comparison would be the battle of 12 November 1942, where 21 Japanese twin-engine torpedo bombers attacked six American transports off Guadalcanal protected by three heavy cruisers, two light cruisers and eleven destroyers, about half the AA potential as the seven battleships, three light cruisers, and nineteen destroyers that might have been steaming off Pearl Harbor on 7 December 1941. A view of that action was related by a gunnery officer on the destroyer Sterrett:
Now I gave the gun captains the signal they had been waiting for—“Commence firing! Director control. Rapid, continuous fire.” The crews loaded the shells and powder cartridges into the guns, and in four seconds the first salvo was on its way. The concussion was terrific, but by now we were used to it. Our first bursts were low and short, so we changed our trajectories. We were the ship closest to the attackers, and our tracers were headed straight at the lead plane. On our third salvo we made our first kill. With a tremendous explosion and a huge cloud of smoke our target fell out of the sky, its tail section completely demolished. The plane hit the water with a crash, skidded, tumbled, came to a stop, and burned like all the fires of hell. We shifted our sights to the next plane in line and immediately hit it squarely. It simply disintegrated in the air—big chunks of airplane splashed into the sea across a wide area.