Attack on Pearl Harbor (10 page)

A trap of wargaming is the assumption of godlike powers by umpires and admirals. Games proceed under conditions that they deem realistic, even if they are based on judgments that others might question. In the Japanese games there were disagreements over some decisions, but the purpose of a chart exercise is to bring such disagreements out into the open for consideration.

The game’s Japanese critics should not be ignored. There were flaws in the game and gaming process, and judgment calls by the umpires and admirals that were questionable. However, the Japanese wargaming effort was more robust, less arbitrary, and more productive than Prange’s interpretation would suggest. Certainly it was not perfect; in the Midway game there were elements of the “Victory Disease” that infiltrated Japanese attitudes and thinking, along with a sense they would win regardless of what the Americans threw in their path.

Victory Disease had yet to taint the environment when Yamamoto held the first of several wargames to examine the Pearl Harbor attack—more the opposite, as most Japanese naval officers were in awe of the magnitude of what they were about to attempt. These wargames seemed genuine, with perhaps some staging by Yamamoto to help socialize acceptance of his plan with other senior officers. They were games to explore operational alternatives, and not merely to put an existing plan to the test. As such there appears to be fewer interventions by senior officers, although there were some rather improbable judgments that, as will be seen, reflected the role the gods were assigned to play.

The First Games

The first of the wargames were played on 16–17 September 1941. The Japanese allocated all four of their active fleet carriers to the striking force. The carriers were spotted before they launched their attack, alerting Pearl Harbor’s defenses. The Japanese strike met heavy resistance from interceptors and AA. Half the strike aircraft were shot down,
¹¹
losses on the order of 106 to 127 aircraft (depending on the composition of the strike). Only “minor” damage was inflicted. Counterattacks by US aircraft sank two carriers and damaged the other two. The attack was a disaster.

The next day the game was re-run with some modifications. The plan was modified so that the carriers made a high-speed overnight approach to arrive at the launch point before the American scouts were in the air for their morning search. Surprise was achieved. The strike was judged to have sunk four battleships and severely damage one, sunk two carriers and severely damaged one, and sunk three cruisers, with three cruisers heavily damaged. One hundred and thirty US aircraft were destroyed,
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50 in the air and 80 on the ground. US counterattacks sank one carrier and severely damaged another. While withdrawing, a fortuitous (probably umpire-generated) rain squall screened the Japanese fleet from further damage.
¹³

The attack was deemed feasible, but heavy Japanese losses were expected.
¹⁴

Details of the game rules and damage assessment formulae, along with details of the composition of the strike, are not known, along with details such as how many B5N Kate bombers carried torpedoes, and what proportion of the D3A Val dive bombers were allocated to hit ships and what proportion were allocated to airfield targets. The D3A Val dive bomber had at this time demonstrated (in training) a 50 to 60 percent hit rate, but B5N Kate torpedo bombers had yet to solve the shallow water problem. Rigorous training in April of 1941 had increased the B5N Kate level bombing hit rate from 10% to 33%.
¹⁵
But, with the uncertainties in how the Japanese composed their strikes, there is insufficient information to reproduce the calculations for each weapon, and how the stated result was achieved.

The wargame serves as a benchmark to what the Japanese believed an attack with four carriers might accomplish. If the enemy was alerted and had their air defenses ready, the Japanese felt that there would only be “minor” damage inflicted. If surprise was attained, the damage inflicted by the four carriers would be enough to immobilize the main body of the US Pacific Fleet for the needed six months. But only 130 of the estimated 550 American aircraft on the island would be destroyed, leaving sufficient air power for strong counterattacks. Consequently, the risk was deemed high. “At the September war games, even with the umpires bending over backwards in favor of the home team, all had agreed that they must anticipate the sinking of several carriers.”
¹⁶

Part of the “bending over backwards” perhaps involved the anticipated hit percentages against the fleet. In this wargame, four Japanese carriers accomplished more damage against warships than was accomplished in the actual attack with six carriers.

It may have been that the Japanese saw that the level of effort used in this wargame achieved sufficient damage against the fleet targets, but there were shortfalls in the damage inflicted on American air power. So, when
Shokaku
and
Zuikaku
became available, they were pulled into the attack plan, and the bulk of their aircraft was directed to the offensive counter-air (OCA) role.

Another alternate possibility is that the aircraft in the actual strike did not achieve the hit rates and fire distribution expected of them, so the six carriers, in reality, caused less damage then was predicted for the four carriers in the wargame.

Another optimistic assumption was that one A6M Zero was the equivalent of three enemy fighters—when one officer tried to challenge “such stupidity” he received a “sharp admonition.”
¹⁷

Another Round of Games

Beginning 13 October 1941 another wargame was held on the flagship
Nagato
, with Yamamoto as host. This time the striking force had only three fleet carriers—
Akagi
was pulled out at the insistence of the Naval General Staff to support the attack on the Philippines.
¹⁸

In this game surprise was achieved, but only “moderate damage” was inflicted. How the damage was assessed is again unknown, as is the threshold between “major,” “moderate,” and “minor” damage. The Japanese warships took no damage, but the operation was seen as “less than satisfactory.”
¹⁹

One might suspect that Yamamoto welcomed the verdict of “moderate damage” inflicted by the three carriers—that is, if he hadn’t set up that outcome—since that usefully established the need for more carriers in the minds of the attending Naval General Staff officers. In addition, the Japanese force escaped without damage, another result that Yamamoto would welcome in his campaign to obtain approval for the attack.
²⁰

A few weeks later Yamamoto asked for and got all six fleet carriers.

Not all the discussion was on the expected offensive results of the operation. Many of the planners emphasized bringing the precariously vulnerable carriers back to home waters quickly and safely. The need for repeated attacks against Pearl Harbor did not come up during the wargames, although two of Yamamoto’s planners—Genda and Commander Sasaki Akira, Yamamoto’s Air Staff Officer—talked about the possibilities before and after the exercises. Nevertheless, in front of the flag officers the exercise concentrated on what could be accomplished against the American fleet units in a single strike of two waves, and the costs in terms of aircraft and carriers damaged and sunk.
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Summary

The wargame results established mental models of expected outcomes (cause and effect) in the minds of the attending officers. These models can be summarized as follows:

The possible Japanese losses were daunting—they were losses on a strategic level, losses that could influence the course and outcome of the war as a whole. And yes, there were opportunities for the umpires to inject bias—Admiral Kusaka thought “the results depended too much on the various personalities of the umpires.”
²²

The Japanese were never ones to allow calculations of material forces (or a roll of the dice) to take precedence over their deeply held belief in the primacy of fighting spirit and the unquantifiable superiority of Japanese crews and equipment. These games were “mere mathematical exercises.” They ignored the factors of luck and divine guidance, factors that the proponents were sure favored the Japanese.
²³

In spite of the gods’ expected bias, the word that filtered down to the aviators was that they faced a fifty-fifty chance of dying for their Emperor.
²⁴

To Yamamoto, whatever the circumstances, whatever the potential for losses, the effort had to be made. He was adamant. The issue went beyond logical argumentation. In an exchange with one of his most intransigent opponents, Yamamoto “put a hand on Kusaka’s shoulder and said with an air of utter sincerity, ‘Kusaka—I understand just how you feel, but the Pearl Harbor raid has become an article of faith for me. How about cutting down in the vocal opposition and trying to help me put that article of faith into practice?’”
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Western readers, grounded in theories of total war based on calculations of material superiority and firepower, might dismiss this approach as something akin to superstition, an outmoded, backward belief system. If so, they have eluded understanding.

In war, there are only three ways to win: by annihilating the enemy, totally incapacitating him, or by eliminating the enemy’s will to fight. The first two are more in line with Western theories of war, but occur in a tiny number of cases historically. Few wars or battles have been won by annihilation or total incapacitation of the enemy. The overwhelming majority conclude when one side decides to quit.

The Western way of war strives for annihilation but accepts the enemy’s surrender well before annihilation. Changing the enemy’s will to fight is a by-product of material losses. Instead, the Japanese recognized the primacy of the will to fight from the outset, striving for means to convince the enemy to quit without requiring overwhelming incapacitating losses to settle the issue. If this could be accomplished, as in the Russo-Japanese War or the Sino-Japanese War, their relatively small country could successfully win against opponents many times their size. Just because their approach did not work in World War II does not invalidate it—it simply demonstrates that the course to winning a war based on the psychological defeat of the enemy must be carefully charted.

Yamamoto sought to induce despair in the volatile American voting public by destroying an inviolate symbol of naval supremacy, the battleship. He was convinced he had taken the measure of a population that was vocally pacifistic. He did not understand that the loudest voices in the American polity may not be the most representative.

Several times after the wargames he reasserted his determination to make the attack, in one instance announcing, “As Commander-in-Chief I have resolved to carry out the Pearl Harbor attack no matter what the cost.”
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Limitations and Constraints

The attack plan was limited by material, force level, and doctrinal constraints.

Carrier Capacity

Eventually, at Yamamoto’s insistence, all six of Japan’s fleet carriers were assigned to the operation. Added to the four large carriers employed in the wargames were the new carriers
Shokaku
and
Zuikaku
, to be completed only weeks before the departure date, barely sufficient time to work up their flight deck crews. These air groups would be “as green as spring grass.” But these aircraft could carry the volume of bombs needed against targets that did not demand high skill levels.

All six fleet carriers provided the planners with 417 aircraft. Spare aircraft were on each carrier, but they were disassembled and crated and would take a day or more to assemble.

As seen in the chart that follows, the numbers of each type of aircraft are nearly balanced, and reflected the normal complement of the carriers.

Tailoring the Air Groups for the Attack

Only three of the Japanese carriers had sufficient range to make the transit from Japan to Hawaii and back without refueling.
¹
Genda had considered breaking up the normal carrier air groups to preferentially load one type of bomber on those carriers designated for the attack. At one time he considered sending two or three carriers loaded with only fighters and B5N Kates with torpedoes. When the problems with launching torpedoes in shallow water appeared insurmountable, he considered leaving home all the B5N Kates and loading up a few carriers with just D3A Val dive bombers.

Both concepts would require shuffling aircraft and aircrew between carriers, a violation of normal Japanese practice. Aircraft and aircrew were considered a part of the carriers’ complement under the command of the ship’s commanding officer, and not an independent command as in the American practice. This was a decided handicap. Later in the war, in cases where Japanese air groups were decimated, as happened to
Zuikaku
and
Shokaku
at the Battle of the Coral Sea, the entire carrier had to be withdrawn from operations until a new air group could be assembled and trained. The American practice of independent air groups that could be assigned to any carrier was much more flexible and effective. For example,
Saratoga’s
air group was shifted to
Yorktown
in the days just before the Battle of Midway, and it was operationally effective in a matter of days.
²

There were transfers from the light carrier air groups to fill out the fleet carrier complements, particularly to obtain sufficient A6M Zero pilots, but a wholesale transfer of B5N Kate or D3A Val complements from one carrier to another had never been previously done, and would likely have generated an instinctive rejection from most senior aviators.

If the B5N Kate aircrews were all concentrated on a few carriers for the attack and then lost at Pearl Harbor, all the surviving carriers would have to carry on the war with an unbalanced air complement. Without B5N Kates, the remaining carriers would not have a killing capability against battleships.

An attack on Pearl Harbor with just the D3A Vals would have lacked killing power against battleships, but could have destroyed carriers and cruisers. This was acceptable to Genda, who considered the carriers the main objective, but would not satisfy Yamamoto.

It is not surprising that both concepts were rejected.

Deck Capacity

With 30 knots of wind across the deck, about 250 feet of deck run was required to launch a fighter, more for the heavily-laden bombers. With carrier flight decks 750 to 850 feet long, 500 to 600 feet were available to stage the aircraft to be launched in one “go.”
³

The first deckload of aircraft would launch and immediately form up and depart to the target. The aircraft remaining in the hangars would be lifted to the flight deck and positioned aft, and then have their engines started for warm-up, a process lengthy enough to eliminate thoughts of having the first group loiter awaiting the second launch so the attack could proceed in a single wave.
⁴
Spotting the deck took approximately 40 minutes, limited by the cycle times of the elevators, with
Kaga’s
the slowest. Engine warm-up took 20 minutes. With these restrictions, the second wave was expected to launch about one hour after the first.
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Doctrine

In 1941 Japanese doctrine had carriers operating in two-ship divisions. Search missions and local patrols would be carried out by battleship and cruiser float planes as much as possible, augmented by carrier aircraft when necessary, reserving the carrier aircraft for offensive missions. The practice was to spot on deck some fighters for CAP and strike escort duties, along with the entire ship’s complement of one type of bomber. One carrier would launch its entire complement of D3A Vals and the other its complement of B5N Kates, whereupon they would join into a single combined-arms strike. This allowed unit integrity, with each bomber type under its own commander from its own ship operating with the men they knew and with whom they had trained. Their attacks would have a greater cohesion than if each carrier launched mixed groups of bombers.

This was good doctrine. Throughout the war the Japanese were able to launch and form up strikes in a minimum of time, something with which the Americans had problems until later in the war.
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But it did constrain the Japanese from deploying their aircraft largely on a unit basis. In contrast, the American practice was more “mix and match,” launching deckloads of mixed bomber types and mixed squadrons to meet the requirements of the specific mission and immediate availability of aircraft.

Vulnerable Torpedo Bombers

The torpedo bombers had to lead the attack. These aircraft were restricted to an unusually “low and slow” attack profile to accommodate the narrow launch envelope required by the modified shallow-water torpedoes, making them easy targets for AA gunners. The torpedo bombers had to slip in their attack before the AA gunners were awake, oriented, armed, and firing.

Aircrew Training and Experience

The air groups on
Zuikaku
and
Shokaku
were only recently formed and many of the aircrews were young and inexpert. In the words of one Japanese pilot, they were “really green” with “very little flight experience.”
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It would be most reasonable to assign them the easier and less critical missions requiring less skill and precision—which meant OCA, airfields and aircraft.

Fighter Employment

The Japanese fighters were considered offensive weapons, not defensive, in the sense that they were expected to range out and attack the enemy, not sit back in a defensive role as escorts or CAP. Their thinking was that “offense was the best defense” when it came to ensuring that their bombers made it through.

As previously mentioned, SEAD against ground targets was a neglected capability and not really in their repertoire or their mindset in 1941. However, the fleet practiced SEAD in attacking warships at sea. An “out of the box” thinker might see the need to apply this cooperation in the Pearl Harbor attack.

Genda, the lead planner, was a fighter pilot. For all his reputed brilliance, his thinking was firmly within the usual Japanese fighter pilot paradigm, locked in the box.

“Stovepipe Thinking”

Japanese doctrine characteristically lacked a combined arms approach, a deficiency called (in modern terminology) stovepipe thinking. There was little inclination to solve problems in a mutually cooperative manner. Dive bombers, torpedo bombers, and fighters all had their separate missions. The concept of having one type assist another type perform a mission was not in their worldview. They certainly considered the best order for the aircraft types to deliver their attacks, but this was to facilitate the individual attacks and reduce mutual interference, more than out of any motives of cooperation or mutual support.

The Japanese would recognize the need to break out of their stovepipe thinking later in the war, but would never really succeed.

Air-to-Air Communications

Important planning considerations rested on the ability of aircraft to communicate. Inter-aircraft communication capabilities define how much control a commander has over his forces aloft, his ability to adjust to circumstances, the flexibility to take advantage of unforeseen errors by the enemy, or even just to allow switching from one plan to another. Good communications allow better coordination of forces and dissemination of sighting reports and on-scene intelligence. Most significantly to the Pearl Harbor attack force, it would allow control of the force by a commander with better overall situation awareness, in particular, the ability to control fighters and the ability to control the distribution of the bombers to gain the best effect from each bomb and torpedo.

This is a significant capability. The attack would be the first combat action for nearly all the Japanese aviators, as most of the aviators on the newly commissioned carriers were young, mostly under 20, and would need supervision by more experienced hands, but also because the second wave would need information on the damage caused by the first wave to optimize their targeting.

It wasn’t until 1940 that the Japanese Navy first established its own capability to produce and install radio sets for aircraft, and 1941 when plans were established to retrofit radio sets into existing aircraft on a large scale. Even then, their production goals were woeful—for 1942 they planned to produce four types of long-range aircraft HF radios for a total of 1,000 sets per month, and only 100 short-range aircraft radiotelephones per month, at a newly established plant at the Numazu Ordnance Depot.

The standard was to have each multi-seat carrier aircraft carry an HF set and a radiotelephone, and each fighter carry a radiotelephone, by December 1941. All the aircraft of the
Kido Butai
may not yet have been fitted in time for the attack.
⁸

The standard of installation was poor. The radios were practically unusable. The bulky sets were jammed into aircraft not designed to accommodate them, and little consideration was given to ensure the sets could be worked. Controls often could not be manipulated to exact settings. The sets did not fare well in a high-vibration environment that varied from steamy hot to sub-zero. Controls might be awkward to reach and dial scales out of sight. Vibration caused knobs to drift off their settings. Operating the sets at high altitude was nearly impossible. The aviators complained that some installers were more interested in getting credit for the installation than in leaving a working radio. Testing was perfunctory and haphazard. Careless supervision and poor installation resulted in wiring problems and electrical grounds. The discharges of engine spark plugs would interfere with reception.

Lieutenant Commander Arima Keiichi, a dive bomber observer assisting the research department in 1944 to develop communications equipment, testified:

The air crews, particularly fighter pilots, became indifferent to the use of their radiotelephones.
¹⁰
Radios interfered with fighter pilots’ concept of themselves as independent samurai warriors. Lieutenant (junior grade) Harada Kaname, a
Soryu
A6M Zero pilot, related that at the time of Pearl Harbor:

Radio communications problems were not unique to the Japanese Navy. CDR Scott Smith, speaking of the first six months of the war, attested that “radio communications in those days was just short of miserable.”
¹²
In particular, intermittent communications between the escort fighters and the bombers at the Battle of Midway was a contributing factor in the horrendous losses suffered by the torpedo bombers.

These problems continued and were evident particularly at the Eastern Solomons and Santa Cruz battles. American aircraft radios tended to drift off the precise frequency required by the sensitive voice transmitter. After the Battle of Santa Cruz, one angry flight commander who had lost communications with two-thirds of his aircraft, wrote: