by Attack on Pearl Harbor: Strategy, Combat, Myths, Deceptions
Ironically, the young aviators from Shokaku and Zuikaku would turn in a sterling performance, greatly exceeding expectations and outshining the dive-bombers from the more experienced carriers.
Level bombers were inefficient against dispersed aircraft and aircraft revetments. However, administrative buildings, hangars, and refueling and rearming facilities were large area targets, the destruction of which could do much to delay and disrupt the dispatch of a retaliatory strike. While the effects of destroying these targets are more difficult to quantify, they are real. Bomb damage would cause confusion, disrupt communications, and interrupt vital functions, as well as inflict personnel casualties. Little details could have huge ramifications—for example, the ammunition for many of the Army fighter squadrons was locked in their hangars and could not be retrieved when the hangars were on fire. If the administrative areas were destroyed and sufficient support personnel casualties inflicted, the process of organizing a strike, loading and fueling bombers, coordinating bombers and fighters, briefing crews, and dispatching an attack to the right location could be disrupted.
The level bombers might also be directed against aircraft on the tarmac and parking areas, but if the American aircraft were properly dispersed it would be a very inefficient use of the bombs. Aircraft near hangars were at risk of being destroyed when the hangars were attacked, but those aircraft would mostly be undergoing maintenance and not ready to fly.
Fighters could also contribute to the OCA effort. A rule of thumb used by combat modelers in the 1950’s and 1960’s was that strafing aircraft would destroy between 0.25 and .50 aircraft per sortie. This would add another 20 to 40 aircraft to those killed by the dive-bombers, for a total of 38 to 94 aircraft destroyed on the ground.
The Japanese optimistically expected more—they typically rated their A6M Zero fighters as three times as effective as an Allied fighter in their wargames.26 Scaling off their wargame results, it appears that the Japanese would have expected 195 US aircraft to be destroyed in the air and on the ground. The calculations indicate that the Japanese expected a large contribution from their fighters.
The Army Air Corps had 57 bombers and 152 fighters on the island. The Navy had 301 aircraft, mostly utility types at Ford Island in maintenance or storage, but there were 61 combat-capable fighters and scout bombers. The Japanese would therefore need to direct attention to the Navy airfield at Ford Island and the Marine field at Ewa. They could reasonably expect to destroy only a fraction of the aircraft on the island. Even an outstanding success would leave 350 aircraft.
These calculations apparently agree with the Japanese assessments since, in their wargames, even when they achieved surprise the US forces mustered a counterattack. This explains why the Japanese allocated so many aircraft to the offensive counter-air mission. It explains the very real need to include strafing fighters against the airfields to hit the many aircraft expected to survive the bombing.
In retrospect, it is hard to predict if an AAC counterattack would have been as effective as the Japanese feared. Attacking ships underway was a specialized skill that required considerable practice. The AAC aviators had certainly demonstrated flashes of brilliance. In an exercise in August 1937, Army bombers attacked the target ship Utah, and on one day hit with 23% of their bombs from altitudes from 8,000 to 18,000 feet. Over the entire exercise they scored 11.9% hits.27 If those hit percentages were duplicated, Pearl Harbor’s 57 medium and heavy bombers carrying four bombs per aircraft had the potential to score 27 (average) or 52 (best) hits, sufficient to destroy all the Japanese carriers.
Once the war began, however, the AAC did not live up to expectations. From 7 December through the Battle of Midway, AAC bombers managed exactly one hit on a warship, on the heavy cruiser Myoko at anchor off Davao in the Philippines, on 4 January 1942.
The Potential Air-to-Air Battle
The Defender’s Aircraft
With warning, a large portion of the 152 AAC fighters could have been airborne to meet the attack. The first wave of the Japanese attack included 45 fighters- 1 to 3.4 would have been steep odds for the Japanese to overcome.
However, there are additional considerations.
Only 99 of the US fighters were the latest generation P-40 aircraft, the rest being P-36’s and P-26’s.
The Curtiss P-36 Hawk was a fairly recent aircraft, first delivered in 1938. It had a decent combat record when flown by the French against the Messerschmitt Bf-109 in the Battle of France, so its combat capabilities were creditable.
The Boeing P-26’s performance and armament was two generations behind the A6M Zero. The P-26 “Peashooter” an insignificant speed advantage over the D3A Val or B5N Kate28 and was armed with only two 0.30-cal machine guns. But they were fighters, and could be dangerous to the lightly constructed, flammable Japanese bombers, particularly if they caught a torpedo-laden Kate lumbering low and slow towards the harbor.
Aircraft Availability
Many of the fighters would be undergoing maintenance or repair. In the Hawaiian Islands on 6 December 1941, 37% of the fighters overall, and 55% of the P-40s, were unavailable. This was an unusually high number of aircraft out of commission for maintenance.
To place these percentages in context, during peacetime a force that is able to stop flight operations and concentrate on “peaking and tweaking” its aircraft for maximum availability in advance of an important operation could be expected to have 80 to 90% of its aircraft FMC (full mission capable). In spite of every effort, though, there were the “hangar queens,” aircraft that required a part that was not available locally or which otherwise defied repair. Supply systems are notorious for running out of parts.
At least one fighter squadron took its aircraft out of service every weekend to remove and clean the guns.29 In early December many more aircraft were out of service than usual because the 14th Pursuit Wing had just come down from a lengthy period of heightened alert on the 27th of November. Aircraft were taken out of service to address the backup in routine maintenance and engine overhauls that such an alert leaves in its wake. Of the 12 B-17s on Oahu, half were out of service, mostly cannibalized for parts.30
During the war availability rates would plummet, reduced by battledamaged aircraft that required more difficult repairs, lack of parts at forward locations, and lack of maintenance facilities. Availability percentages of 50–70% were not unusual for US forces, 30% or less for Japanese forward forces. The environment was a significant factor. Jungle heat, humidity, and desert sand were particularly hard on airframes and engines. Early in the war in the Pacific or North Africa theaters, 50% availability rates were a noteworthy accomplishment.
At the beginning of the war Japanese maintenance crews were good and well supported from their jumping-off bases. They also had the luxury of knowing when the war would start. Most Japanese units were 90% FMC or greater. Spare aircraft were assigned both to land-based squadrons and on board the carriers, so most Japanese squadrons went into early battles at full strength.
Japanese carriers could carry three aircraft of each type disassembled on board to replace battle-damaged aircraft. American carriers also often had spare aircraft in a partially disassembled state, either broken down and boxed or partially disassembled and triced up into the overhead of the hangar.
Later in the war the Japanese grappled with shortages in maintenance personnel to replace those killed and those isolated in bypassed bases. They did not have the pool of mechanically adept young men used to working with automobiles and machinery as did the Americans, so their maintenance personnel were more difficult to replace. Aircraft availability rates plummeted.
Sunday
The Japanese specifically chose Sunday for the attack because this day usually had the most ships in port. As a side benefit, many of the American pilots and other officers and men would be expected to be away from their bases, at their homes or on liberty at the hotels at Waikiki. Even though officially living in the Bachelor Officers’ Quarters (BOQ), many officers
would band together and rent an apartment on the “civiside” of the island. Sunday, if the island was not on alert, would have the fewest number of immediately available fighter pilots.
Fighter Employment Doctrine
The first-wave fighters had one mission: to destroy enemy aircraft in the air and on the ground.31 Several air-doctrine factors are conspicuously absent.
Missing was any statement that the fighters were to protect the bombers. This is a substantive omission, not just an order-writing oversight. The Japanese fighters were to seek out and destroy the enemy with the freedom to leave the bombers to do this. Just like in China, the bombers were to be protected by having their own fighters killing enemy fighters, rather than chasing US fighters away from the bombers.
This might sound like splitting hairs, but it reflected a significant difference in fighter employment. Nothing told the fighters to stay with the bombers in an escort role, or to maintain a CAP over airfields to prevent enemy planes from getting aloft, or to find and cover the bombers after they dropped their bombs. They were to destroy enemy fighters, not just deflect enemy attacks. They were offensive platforms like the bombers, only with different targets.
If surprise was not achieved, the fighters were not obligated to cover the bombers.
Employment of the Fighters in the Attack
Fighter Sweep
If Kido Butai was detected any time within 24 hours before the scheduled time of the attack, the fleet was still to press on and deliver the attack. However, the composition of the waves would change. All the fighters would be dispatched in an initial first-wave attack. The bombers would only be launched after the fighters had achieved “command of the air.”32 This operation, called a “fighter sweep” in the West, was used in China and by both sides in the unfolding European war and the Battle of Britain.
The objective was to destroy American fighter opposition. Nothing was planned against the AA defenses. The effectiveness of the US AA is explored in detail in a subsequent chapter, but in summary, there was enough AA to make for a Japanese disaster. In addition, with the Japanese samurais chasing air-to-air kills, few would have strafed bombers, so a counterattack could have been expected.
With warning of the attack, the American carriers in the area would have been notified. Halsey undoubtedly would have engaged. It is likely that a full-blown air-sea-land battle would have resulted, with results very different from what was seen historically.
Fighters to the Front
If Kido Butai had not been spotted in advance, a possible course of action would have been to launch a first-wave mixed strike of fighters and bombers, but have the fighters forge ahead and attack ahead of the bombers. Fighters were launched first, because they required less deck length to get airborne. They also had a faster cruising speed than the heavily laden bombers. They could fly directly to the enemy airfields, strafe, and then fly continuous cover keeping enemy aircraft from getting off the ground. If surprise was not achieved, they would engage fighters to clear the way for the bombers.
There were problems with this concept. The first is mass. The Japanese only had 45 fighters in the first wave. These aircraft would have to cover seven airfields, plus accompany seven different formations of bombers.33 This would spread the fighters thin and make them vulnerable to concentrations of enemy fighters, a serious possibility considering that their intelligence expected 200 American fighters.34 Some defending fighters would undoubtedly evade the A6M Zeros and get to the bombers.
One might think that the bombers would be adequately protected by sending the fighters directly against the airfields, especially if surprise was attained. What better way to protect the bombers then by preventing the fighters from ever getting off the ground? But if the enemy fighters were already airborne, the Japanese fighters might miss seeing them and go on to strafe empty bases. With poor radio communications the bombers would not be able to recall the fighters, allowing the defenders the opportunity to attack unescorted bombers
There simply were too few fighters for the first wave to employ fighter sweep tactics.
Close Escort
A second option would be to have the fighters remain with the bombers in a close escort role. In China, Japanese fighter pilots preferred to range freely and dogfight with the enemy, rather than to stick with a bomber formation. Close escort was simply not available in their doctrine or their mindset.
The Plan
The decision was to have the fighters accompany groups of bombers en route to the targets. The fighters would engage enemy fighters in the air or, in the absence of aerial opposition, strafe enemy airfields.
As the first wave flew south, groups would break off and head to their individual objectives.
• 25 D3A Vals and six A6M Zeros would break into two groups to hit Wheeler Field from the east and west;
• 26 D3A Vals and nine A6M Zeros would attack the Ford Island and Hickam airfields;
• 50 B5N Kate high-altitude bombers accompanied by nine A6M Zeros would head for Pearl Harbor;
• 40 torpedo-carrying B5N Kate carrier attack planes would drop down to low altitude and split into two groups to approach Pearl Harbor from the west and the east; nine Zero fighters would accompany the torpedo bombers until they were about 10nm from the harbor, where they would split off to attack Ewa Field.
• 12 Zeros would attack Kaneohe Field.35
The specific orders for the fighters are particularly noteworthy: “The targets of Fighter Combat Units will be enemy aircraft in the air and on the ground.” That wording reflects the Japanese belief in the superiority of the offensive. The order did not say, “Protect the bombers from enemy fighters.” Indeed, it directed the opposite: “In the event that no enemy aircraft are encountered in the air, the (Fighter Combat) units will immediately shift to the strafing of parked aircraft…”36
The fundamental Japanese fighter organization was a shotai of three aircraft, with three shotais combining into a chutai of nine aircraft. All the fighter formations assigned to each of the groups were from a single carrier, with the exception of the Kaneohe Field strike group that consisted of a mixture of Shokaku and Zuikaku fighters. This allocation preserved unit integrity, but maintaining unit integrity imposed a nearly even distribution of fighters across the formations that were disproportionate to the value of each formation.
For example, the torpedo bombers were expected to deliver 27 torpedo hits, enough to sink six battleships. The B5N Kates carrying AP bombs expected eight hits and perhaps to cripple one or two battleships. In other words, the torpedo bombers were three to six times as valuable as the high-altitude bombers. In addition, the torpedo bombers would be the most vulnerable. During their final run to target they would be flying singly, low and slow, in four long strings of bombers with each aircraft separated by hundreds of yards, beyond where their defensive machine guns could provide mutual support. The level bombers would be in five-ship elements with some degree of mutual protection.
These considerations should have caught the attention of the planners. Fighter cover should have been allocated to the torpedo bombers in proportion to their vulnerability and value. The torpedo bombers should have been wrapped in cotton wool and protected at all costs. Instead, the torpedo bombers, with 85% of the killing power, were protected by 20% of the fighters.
Even more inexplicably, the fighter chutai accompanying the torpedo bombers was to split off to attack the Marine Corps Air Field at Ewa, seven miles from Pearl Harbor. The torpedo bombers would make their final approach and attack without any fighter protection over the harbor whatsoever. While the Zeros were absent strafing airfields, the torpedo bombers could have been slaughtered.
This all was exacerbated by the fact that the fighters trained independently. They had not practiced with the bombers, so coordinated support was impossible.
The largest fighter unit was assigned to attack Kaneohe Field. This is inexplicable. Twelve of the available first-wave fighters (27%) were sent against an air
field fifteen miles from Pearl Harbor, to attack a PBY patrol wing. Granted, the “B” in PBY stood for “bomber,” and pre-war aviation theorists actually thought these large, slow, poorly defended aircraft could be a threat to surface ships. Even if they constituted a threat, the PBYs at Kaneohe were not an immediate threat. It would have taken hours to locate the Japanese carriers and load bombs for an attack. A first-wave attack on Kaneohe could not be considered as an anti-reconnaissance measure, since the Japanese fighters were to arrive well after the Americans’ dawn reconnaissance patrols were in the air. This target could have been deferred to the second wave. The primary concern of the first-wave fighters ought to have been enemy fighters, not reconnaissance aircraft.
In a plan featuring many unusual decisions, the most bizarre was that more fighters were assigned to strike a wing of seaplanes than were assigned to ensure that the torpedo bombers reached their target.
The primary mission of the fighters ought to have been to escort the B5N Kate torpedo bombers to the target and provide cover against enemy fighters, along with suppression of enemy air defense (SEAD) if the AA proved formidable (as it did). This was Japanese doctrine for attacking a fleet at sea—there is no reason why it should not have applied to attacking a fleet in port. After the torpedo bombers had successfully attacked, a process of only a few minutes if executed as planned, the fighters could have shifted to strafing airfields. But Japanese offensive propensities, along with their experiences in China, blinded them to the need to provide direct fighter support to the torpedo bombers.
The air groups from Zuikaku and Shokaku assigned to the Kaneohe strike were not held in high regard. Their air groups had only been recently formed out of the scrapings of available A6M Zero pilots. Much of their training in the months before the attack was in flying fundamentals, such as formation flying. It could be that they were shuffled off to the side and trusted to do little more than create some confusion, and delay the American reconnaissance effort.