Alan D. Zimm

by Attack on Pearl Harbor: Strategy, Combat, Myths, Deceptions

  Historically, the 14 fighter sorties that were able to get to altitude achieved 8 to 11 kills.25 At that rate 106 defending fighters flying one sortie apiece would score 61 to 83 kills.

  To those steeped in tales of the invincibility of the Zero, this will seem high. It is high, compared to the early war record of the P-40 in the Philippines and the record of the defenders of Java, Ceylon and Singapore.

  A better metric might be the performance of the US fighters defending Midway the following June. The island’s defenses were alert, and the incoming Japanese raid was spotted by a PBY and by ground radar. There were 28 fighters on the island, 21 F2-A Brewster Buffalos and seven F4-F Wildcats, with one of each unavailable due to engine problems. 26 fighters intercepted the Japanese strike of 72 bombers and 36 A6M Zeros. The A6M Zeros dominated the air-to-air engagement—only a few of the defending fighters were able to get through to the bombers, and all were quickly placed on the defensive trying to deal with “the swarm of Zeros, from one to five of which got on the tail of each Marine fighter.”26

  Of the 26, 10 returned, with only two in a flyable state. The US AR gave them credit for 33 kills.27 In the Japanese AR, 5 to 8 aircraft losses were attributed to Midway’s fighters.28

  Applying these results to the defense of Pearl Harbor would give between 20 to 33 Japanese aircraft lost to defending fighters, compared to the 61 to 83 kills with the previous methodology.

  The most probable result would have been somewhere between the extremes. At Midway there were factors that reduced the effectiveness of the fighters compared to the situation at Pearl Harbor:

  1) The US fighters were outnumbered, 26 to 36.

  2) The US fighters were a “pick-up team” with little experience and training as a team. Some of the pilots had few hours in type.

  3) The US fighters were committed piecemeal, in an uncoordinated manner.

  4) The F2-A Brewster Buffalo was seriously outclassed by the A6M Zero.

  At Pearl Harbor, the US fighters could have outnumbered the first wave of Japanese fighters, 43 Japanese to 106 US. They were experienced flyers with lots of hours in type and training together as a team. The Japanese strike was fragmented, with the Japanese fighters scattered among their many ground targets in penny packets. And, the P-40 and P-36 fighters could be effectively flown against the A6M Zero with the appropriate tactics.

  At Pearl Harbor the US fighters got aloft after the Japanese fighters had abandoned their covering mission and were concentrating on strafing. The American fighters were protected by the fact that they were so few among so many—by the time they got into action, most of the Zeros were “target fixated” on ground targets and had dismissed the possibility of seeing any defending fighters aloft. Some of the US sorties were initially unnoticed until they opened fire for their first kills.

  The 14 fighter sorties that did get off were piloted by exceptionally aggressive and skilled aviators. One witness noted that when aviators recognized they were under attack there was a general scramble for available aircraft, but some of the pilots were not running as fast as others. The ones that got aloft really wanted to fly, leaving behind their less confident compatriots.

  A study conducted of 800 Korean War fighter pilots found that half did not achieve any kills, while less than 10% of the pilots achieved over 50% of the kills. The pilots that did get aloft were more likely to be in this latter group, more aggressive and more skilled than the average pilot. If 106 aircraft had been airborne all of the pilots would not have achieved the same rate of kills as in those 14 sorties.

  There are arguments for accepting the higher figure. It is known that the P-40 could be effective against the nimbler Japanese fighters. In China, Claire Chennault devised a set of tactics for the Flying Tigers that gave the advantage to the P-40s, and the American Volunteer Group racked up a confirmed 15:1 kill ratio.29

  Several things contributed to the poor early showing of American fighters in the Pacific, particularly in the Philippines. There was a lack of intelligence information and appropriate tactics to counter the A6M Zero. Good intelligence would have driven them to the same conclusions as those reached by Chennault: American fighters should not dogfight with the Zero. Second, at the Philippines many of the US pilots were very junior, some just out of flight school and then with no flying time for months during their sea voyage to the islands. Many had only a few hours in type,30 and were flying aircraft that sometimes literally had just been assembled, with engines not broken in for high-performance flying.

  These conditions did not apply in Hawaii. “The pursuit squadron commanders and most flight leaders were all seasoned pilots with nearly 1,000 hours of flight time. Many of the junior pilots were from the Flying Class of 1940D but still logged 500 to 600 hours, half of it in fighters.”31

  This can be compared with the pilots of Kido Butai, who averaged 800 hours, with about 10% of the pilots with combat experience in China.32 But the 800 hours figure was an average, and included all types of aircraft. There was a shortage of Zero pilots for the Pearl Harbor attack, and many of the very young and very inexperienced were prematurely transferred to carriers. Their training for the months before the attack concentrated on flying fundamentals—take-offs and landings, carrier qualification, navigation, and formation flying.

  The 14th Pursuit Wing at Pearl Harbor did not lack information on how to properly kill the A6M Zero. Chennault had passed through Oahu in July of 1941 and took the time to make a presentation to the Army pilots. One of them recalled:

  The meeting was held at the Wheeler Field officers’ club and was packed. Chennault was a spellbinder who spoke for nearly three hours. He told us his experiences in China and reviewed the quality of Japanese flyers and their new fighter, the Mitsubishi Zero. He said that we would be surprised at its agility and sharp-turning characteristics.”33

  This visit was reinforced by several documents that were distributed in Army and Navy aviation circles. Major James H. McHugh, USMC, the Assistant Naval Attaché for Air in China, filed a report based on an interrogation conducted by the Chinese of a captured Japanese pilot. It provided accurate information on the fighter’s speed, armament, and rate of climb. Lieutenant Stephen Jurika, Jr., USN, the last pre-war US Navy Attaché for Air in Japan, attended an aviation exhibit in Tokyo and, in a monumental security lapse by the usually paranoid Japanese, was allowed to sit in an A6M Zero. He copied all the information on the aircraft’s side plate and the labels inside the cockpit, and filed a report with the Office of Naval Intelligence. Another report on the A6M Zero’s characteristics was filed by Major Ronald Boone, USMC, in the summer of 1941.34 Chennault himself had written a report on the A6M Zero which he delivered to General George Marshall on 12 December 1940. A few days later Marshall told a conference about the new Japanese fighter which had effectively eliminated the Chinese Air Force. Marshall passed on the information in a letter to General Short in February of 1941.

  The Army had good pilots in Hawaii who knew their aircraft and would not be surprised by the quality and performance of their enemy. The Zero pilots were not overwhelmingly skilled or experienced. Chennault undoubtedly passed on his tactical ideas that led to the 15:1 kill ratio for the Flying Tigers. Given all that, the kills-to-sorties ratio achieved at Pearl Harbor, 8 to11 kills in 14 sorties (officially, 9 kills and 4 probables), is understandable. There is less reluctance to extend this ratio to a full battle with 100-odd defending fighters with a 2.5:1 advantage in numbers.

  The Japanese expected high losses if the Americans were alert. In their first September 1941 wargame, an American scout reported the approach of the Japanese. The first wave

  encountered a swarm of interceptors which kept it so busy fighting its way to the targets that it could not bomb effectively. At the same time ship guns and shore batteries blazed away at the attacking planes, dropping them like ducks over a hunter’s blind,… Half of Nagumo’s aircraft scrambled back to their carriers, having inflicted only minor damage to the ships in Pearl Harb
or and the military installations on Oahu.35

  Aircraft combat losses can also be estimated using loss rates predicted in the Naval War College Maneuver Rules. Losses are calculated as a percentage of the attacking and defending numbers. Fighters were allowed two engagements per sortie.

  For the first wave, 43 US fighters would be engaged by 43 Japanese A6M2 Zeros, while the remaining 63 US fighters went for the bombers. Losses would total 34 US fighters and 38 Japanese planes, 12 of them fighters and 26 bombers.

  The NWC air–to-air combat formulas remained unchanged between 1941 and 1945. In the 1946 rules, the equations for air-to-air losses were revised to take into account wartime experience. Using these rules 8 US fighters and 50 Japanese aircraft, 12 fighters and 38 bombers, would be shot down.

  The NWC rules allowed the surviving US fighters to return to their bases to be re-armed and re-fueled and sent up again. The P-40s were based at Wheeler airfield, about 8 miles northwest of Pearl Harbor, so flight time would be short. The NWC rules specified the required ground turnaround time. 60 fighters would be aloft to engage the second wave, 40 with two engagements and 20 with time for one. This likely overestimated the turnaround time at Wheeler, where most aircraft had individual ground crews, revetments, and service equipment. Aircraft could also be serviced by outlying airfields, reducing the queue at Wheeler.

  The Japanese second wave was to consist of 33 A6M2 Zero fighters, with bombers bringing the total up to 167 aircraft. Using the same assumptions as before, the 1941 NWC rules would result in 12 US fighters and 16 Japanese aircraft (nine fighters and seven bombers) lost. The 1946 rules give six US fighters lost, with nineteen Japanese (nine fighters and ten bombers) shot down.

  The NWC rules have weaknesses.

  • None of the tactical details of the encounter are considered, such as altitude advantage, cloud cover or the presence of AA. Bombers had the same chance of being shot down in formation as they had when flying alone.

  • The individual qualities of the fighters are not considered. A P-26 with two .30-caliber machine guns was given the same effectiveness as an F6F with six .50-caliber machine guns.

  • The numbers of aircraft involved are not considered. Kill rates drop off in large encounters—fighters with a 30% chance of a kill in a 4 v. 4 encounter might have a 20% chance of a kill in a 50 v. 50 fight. With more aircraft in the “fur-ball,” pilots had to spend more time evading enemy fighters and had to abort more attacks when other aircraft got on their tail.

  • The odds are not considered. In the formula, four fighters would shoot down the same number of enemy aircraft if they were engaging four of the enemy or forty.

  • Skill and training are not considered. Nuggets just out of training achieve the same results as veterans.

  • The NWC formula allowed for only two engagements by each fighter. This is low.

  The NWC approach was designed as a “quick and easy” way to inject air combat losses into a wargame that was being executed with judges performing all the calculations with pencil and paper. It was designed to give expected value, approximate results on an operational level. It reflected the informed expectations of aviators during the interwar period; after the war, it was changed to reflect combat experience. The calculations provide a reasonable first-order estimate of losses in an air-to-air action.

  The scenario calculated above does not include the 15 USMC F4F Wildcat fighters at Ewa Field, 14 of which were operational. If the AAC fighters engaged the first wave, Ewa would likely not have been strafed and these F4F Wildcats might have been able to join the battle. The Marines could have contributed an additional 16% to Japanese losses.

  Full Army AA Alert

  The Army conducted a full-scale seven-day exercise just prior to the attack. All AA guns were deployed and supplied with live ammunition. But, as related by a Provost Sergeant assigned to the defense of Bellows Airfield, “On Saturday, 6 December, we were told to take down all arms and lock [them] in [the] Armory and take our passes to Honolulu.”36

  The AA unit assigned to protect Ford Island was quartered 15 miles away at Camp Malakole. Daily the guns were trucked to Pearl Harbor, complete with ammunition. They arrived at Ford Island by ferry. 7 December was the first Sunday in months this task was not performed.37

  If the Japanese had attacked during the Alert, 19 mobile 3-inch batteries totaling 76 guns would have been added to the defenses.38 They could have accounted for an additional 12 to 48 aircraft destroyed. The combined Army three-inch AA batteries could have destroyed 18 to 78 aircraft.

  Each of the airfields had an assortment of 20mm, .50-cal, and .30-cal machine guns available for perimeter and overhead defense, along with small arms. It is very difficult to make an estimate of enemy losses from these weapons, as it would require knowing how many aircraft came within range. These short-range weapons may have shot down as many as 4 aircraft in the attack. The contribution of these weapons can be included by adding the 4 historical kills to the estimates.

  All the Defenses Combined

  Adding together the potential Japanese losses from all sources gives the following low and high-end estimates.

  This is a first-order estimate only. Calculating losses independently and then adding them will tend to overestimate losses—more aircraft shot down by fighters would mean fewer targets for the AA guns, and so on. The point of the calculation is to approximate the magnitude of Japanese losses to see if the American defenses were “inadequate” as claimed in many history books.

  If the American defenses had been active as they should have been, the Japanese would have suffered stunning losses, and the damage to the Pacific Fleet would have been considerably less than what was actually experienced.

  Losses most likely would have been on the order of 50% of the attacking force. This is in line with aircraft losses in the 1942 and 1943 aircraft vs. ship battles. At the Battle of the Coral Sea, the Japanese lost 30% of their aircraft, and the carriers Shokaku and Zuikaku were put out of the war for approximately a year working up replacement aircrews. At Midway, Hiryu launched two strikes against the US carriers that suffered 63% losses. The US torpedo bombers at Midway took 86% losses. On 20 February 1942, Lexington was attacked by 18 land-based twin-engine Betty bombers and 16 were shot down, for 89% losses. On 12 November 1942, 21 Betty bombers attacked an American task force off Guadalcanal and suffered 95% losses. The Japanese aircraft losses at Pearl Harbor could have been equally horrific.

  The following table shows the Japanese fleet carriers and their active aircraft capacity. If the Japanese took any significant losses from their air groups in the Pearl Harbor attack, it is likely that they would consolidate their air groups, stripping some carriers to keep the others operational. The table shows what carriers might be forced out of service due to lack of aircrew:

  In other words, the Japanese fleet would have had one-third to two-thirds of their fleet carrier force placed out of action, and might have had only two carriers with their smallest aircraft capacity remaining in service, with the others out until late 1942.

  Japanese aircraft were also in short supply. In the above scenario an additional 50 to 75 aircraft might have been damaged beyond repair—in the actual battle 20 damaged aircraft were jettisoned as unserviceable. With those additional aircraft losses another carrier would have been out of service for some months awaiting replacement aircraft.

  The Japanese were short on manufacturing capacity for naval aircraft, and had no reserve A6M Zeros. Two Japanese light carriers were not fitted with combat air groups in the early months of the war due to lack of aircraft and aircrew. Two active light carriers, Hosho and Ryujo, started the war with obsolescent A5M Claude fighters, aircraft with fixed landing gear, and continued to carry these aircraft for months.

  Conclusion

  If the Japanese had attacked just a few days earlier, while the Army defenses were in Alert 2, they would have lost enough aircraft and aviators to put one-third to two-thirds of their fleet carriers out of se
rvice. The Japanese could have conceivably lost more than half of their total stock of experienced carrier-qualified aviators. This would have had a significant effect on the course of the war in the Pacific.

  CHAPTER TEN

  ASSESSING THE FOLKLORE

  A mass of folklore has developed concerning the attack on Pearl Harbor. Stories, assumptions, unverified witness reports and other tales have been passed from source to source with little critical examination.

  1) Japanese “Superpilots”

  Before the war most Westerners had little respect for Japanese aviators. Among many odd beliefs, Americans thought that the Japanese had defective vision (stereotypically, the Japanese in pre-war movies characteristically wore glasses, especially the bad guys), and a genetic predisposition towards defective balance, making them poor pilots. Many believed Japanese aviators were not capable of executing so complex a task as an attack on Pearl Harbor.1

  From the depths of contempt, after Pearl Harbor the Japanese aviators were hoisted to the status of demigods. Reinforced by their successes in the first six months of the war, legends have developed around the pre-war trained core of Japanese carrier flyers, that they were super-aviators, masters of aerobatics, consummate warriors, and all seasoned veterans of the China Wars. One historian claimed that “many” of the Pearl Harbor attackers had “hundreds of hours of combat flying experience.”2 “Japanese aviation abilities, heavily downplayed by the United States and Great Britain before the war, were suddenly accorded almost mystical reverence.”3

  Some of the perpetrators of this myth have used statistics to bolster their claims. “The average flight time of a US Navy pilot in December 1941 was 305 hours against an average of 700 in the entire Japanese Navy and up to 2,000 in the Pearl Harbor strike force,”4 intoned one source.