Attack on Pearl Harbor (11 page)

American radios were superior to Japanese equipment. Judging from the Americans’ problems, one can imagine the challenges Japanese aviators faced.

The Japanese mostly ignored their nearly inoperable voice radio equipment. Anecdotally, it appears that little (if any) use of the radiotelephone was included in Japanese plans for Pearl Harbor, or used in practice. Communications appeared restricted to limited HF continuous wave radio, Morse signals, and visual signals. The famous attack order,
Tora Tora Tora
, was sent over keyed HF. Flares were used to communicate “surprise” or “no surprise.” When the flares were misinterpreted, veterans did not mention any attempts via radiotelephone to correct the error and bring the formations back under control.
¹⁴

A poignant incident during the attack shows the norm for Japanese aerial communications. A fighter was leaking fuel and the pilot knew he had no chance to return to his carrier. To his wingman, he pointed to his mouth (the sign for fuel), gestured that his fuel was low, smiled, waved, and rolled his plane into a final suicide dive. There was no attempt to use the radiotelephone, even for last words.

Certainly radiotelephones were in ill repute among Japanese naval aviators at least through 1943, and it is unlikely that they would rely on the equipment for anything tactically critical. There are stories during the Solomons campaign of Japanese fighter pilots personally tearing out their radio equipment in order to lighten their aircraft and gain a bit more speed and maneuverability.
¹⁵

Radiotelephone limitations restricted Japanese planning. Communications deficiencies restricted how ship-killing ordnance could be coordinated. In particular, it forced more responsibility on the leaders of
shotai
and
chutai
in selecting targets and directing the attack. There simply were no reliable communications with higher leaders.

Target Selection and Weapons Delivery

With limited inter-aircraft communications, much responsibility was placed on the shoulders of the aircraft commanders when it came to target selection. The Japanese bombers operated in
shotai
of three aircraft. The
shotai
leader—or, in larger attacks, the
chutai
leader of three
shotai
—would select the target, and the other aircraft would simply follow. However, individual aircraft commanders had the authority to select a different target.

For the D3A Vals, the
shotai
was an important unit, as their divebombing technique had the following aircraft adjusting their aim point based on the fall of the leader’s bomb. If the
shotai
became separated, significantly reduced dive-bombing accuracy could be expected.

Limitations and Constraints—Summary

The planners had significant constraints, some imposed by their equipments, some from their doctrine, and some from the limitations of their own thinking. Recognizing self-limitations was not an area in which the Japanese excelled—a culture where errors could result in suicide tended to limit thinking outside of societal norms.

This analysis will proceed to compare the Japanese planning and attack against what was theoretically possible, while noting the source of the shortfall, whether from doctrinal constraints, mental errors, or errors in execution. An alternative approach, determining a perfect attack within the constraints of Japanese doctrine and thinking, would be very problematic, since characteristically there might be many reasons behind a shortfall, and it might be impossible to determine them all. As will be seen, most of the Japanese shortfalls had solutions that could have been achieved within the technology of the period, if only the problem had been recognized and some thought given to its solution. In most cases the planners were restricted in their ideas of what was possible, and accepted their limitations as a matter of course.

Within the above constraints, the planners had the flexibility to determine the aircraft types to employ in each wave, what targets to hit and in what order, what weapons to use on each aircraft type against each class of target, and how fighters were to be allocated and employed. These issues were significant challenges alone.

Planning for Pre-strike Reconnaissance

The Japanese plan included submarine and aerial reconnaissance immediately prior to the attack.

A submarine would scout the Lahaina Roads anchorage off Maui a day prior to the attack and transmit a report. This would be a fairly lowrisk mission, and the information would be critical. If the fleet was located off Maui at anchor, the attack would have to be redirected and the armament mix changed. The level bombers would not be needed, and those fifty aircraft re-armed with the more lethal torpedoes. If only part of the fleet was out, the attack would have to be split and armed accordingly.

Two cruiser float planes would be launched in the pre-dawn hours before the attack. One was to scout Lahaina Roads again, presumably to check if the fleet had departed the anchorage since the submarine’s report, while the other went to Pearl Harbor for reconnaissance and to transmit a weather report.

Shortly after 0600, with hardly any light to mark a horizon for the pilots, the carriers were to launch the first wave of the attack. At 0630 the battleships and heavy cruisers would launch 16 float planes to scout to the east, south, and west. Japanese reconnaissance doctrine differed from that of the Americans, in that float planes were more used for long-range reconnaissance, while the Americans used carrier aircraft. The Japanese doctrine was good, in that it preserved the carriers’ aircraft for offensive operations, maintained unit integrity, and kept carrier decks from being tied up to recover the reconnaissance aircraft. Its weakness was that the float planes from the battleships and heavy cruisers were stored exposed to the weather, and were not as reliable. In addition, the float plane aviators got fewer hours and were not the same quality as carrier aviators.

Later, at Midway, the American system showed its warts when the three American carriers could not put together a coordinated strike, as one carrier had to delay her launch while recovering reconnaissance aircraft. But the Japanese system made the critical error. A reconnaissance float plane was delayed in launching, making it fatally late in discovering the American carriers.

The second wave would be launched at approximately 0730, one hour after the departure of the first wave.

Fuchida’s Claim Regarding Level Bombers

Fuchida was first introduced to the Pearl Harbor attack plan in a meeting with Genda in late September 1941, immediately after Fuchida was transferred to serve as the strike leader aboard
Akagi
.

According to Fuchida, the plan Genda showed him did not include level bombers with AP bombs. “The Japanese Navy had a terrible record of hits using this technique,”
¹⁶
scoring less than 10% hits in exercises the previous June. In addition, AP bombs had a tiny charge of explosives compared to torpedoes. Aviators in the IJN had argued for some time that level bombing was an inefficient use of resources and would not score enough hits to justify its use. At one point the First Carrier Division recommended that horizontal bombing should be abolished.
¹⁷

Fuchida, a level bombing specialist, claimed he pressed Genda to add level bombers. AP bombs, Fuchida asserted, would be needed against ships inaccessible to torpedoes. He pointed out to Genda two things: torpedo nets could protect all the ships from torpedoes, while double-berthing ships side-by-side would shield the inner battleships.
¹⁸
Fuchida claimed his arguments convinced Genda, and as a result level bombers were included in the attack plan.

This conversation likely did not occur.

First, Fuchida spoke as if Genda was not aware of the implications of double-berthing battleships or of torpedo nets. Considering Genda’s reputation for brilliance, such gaps in his knowledge are highly unlikely.

Second, the Japanese were working on an armor-piercing bomb for the Pearl Harbor attack well before Fuchida’s meeting with Genda in late September 1941. Early in 1941, a 20-meter-square armor plate was set up to test a bomb made from a converted 40cm battleship shell. Tests refined the modifications to improve its penetration capability. At that time it was thought that a release altitude of 12,000 feet was required to get the desired penetration. Production of the bomb was started, and by mid-September 150 had been produced.

Genda had indeed almost given up on horizontal bombing in March of 1941 due to the low hit percentage, which was under 10%. Considering that 12 to 16 hits were considered necessary to sink a battleship, at that rate all the carrier attack planes from all six carriers would be required to sink one battleship. This was unacceptable.

In April, Lieutenant Furukawa Izumi arrived aboard
Akagi
after passing through the bombing course at Yokosuka. In addition, a special team consisting of Chief Petty Officers Watanabe Akira and Aso Yanosuke was formed to work the problem. These men improved the coordination between the pilot and the bombardier. Bombing accuracy improved dramatically, rising in trials to as high as 33% hits. In early June, Genda recommended that the level bombing leaders go to Kagoshima Naval Airfield to train on the techniques developed by Watanabe and Aso. In other words, in June of 1941 Genda put the wheels in motion to include level bombing in the Pearl Harbor attack.
¹⁹

Another set of tests were in process at the time that Fuchida reported for duty at his new post.

Why was another set of tests being run in September when the earlier tests already approved the bomb for production? Evidently, the planners wanted the level bombers to attack from 3,000 meters instead of 4,000 meters to improve their accuracy, but it was not known if the bomb could penetrate enough armor at that altitude.

Fuchida makes the tests a thing of high drama, starring Fuchida. He claimed that Nagumo sent for him immediately after he was informed of Ueno’s problem, saying that the experiment was vital, and “upon it depends the success or failure of the Pearl Harbor attack.” Fuchida and five others hastened to Kashima, and on the third day, from 3,000 meters, scored a direct hit which smashed through an armored plate replicating the
West Virginia’s
deck protection.

The September testing was to determine the altitude from which the level bombers would attack, not whether or not they would be included in the attack. Fuchida did not change Genda’s mind about including level bombers in the attack. The decision had already been made, the bombs already manufactured. When Fuchida arrived on the scene it was just a question of refining the details.

Third, by late September the plan had to have progressed well beyond the point where the Japanese considered that the numbers of torpedo planes and level bombers could be juggled. The B5N Kate carrier attack bombers could fulfill four roles: employing torpedoes against capital ships, AP bombs against capital ships, 250kg GP bombs against cruisers or carriers, or 250kg and 60kg land attack bombs against ground targets. There was undoubtedly considerable calculation regarding the allocations, since they constituted the killing power against battleships or the majority of bombs against ground targets. The idea that Genda accepted a new idea to employ B5N Kates with AP bombs at this late date is not credible. It would have required a complete revision of the strike plan, which had to be near its final form.

The training program began just after Fuchida’s arrival. Training as intensive as the Japanese air groups conducted was not something that just happened, but had to be planned. Airfields had to be prepared, aircraft stationed and prepped, fuel and maintenance and weapons staged, maintenance personnel assigned, housed and fed, and other considerations. The outline of the training plan—locations, aircraft allocations, fuel and maintenance and the like—was likely promulgated well before Fuchida’s arrival. The allocations of B5N Kate bombers between torpedo and AP bombs and OCA had to have been made earlier for the training plan to be ready in late September.

Fuchida’s claim that he was responsible for including level bombers with AP bombs in the strike plan cannot be correct.

Aircraft Allocations

The aircrews were allocated their roles probably early in September. Genda allocated the numbers assigned to each task and each target area.
²¹
He also had the authority to draw additional aviators into the planning process, so he called in a number of experts to help formulate the tactical orders. In addition, he could bring in select
Hikotaicho
—translated literally as “air unit commanding officer,” a position similar to the CAG (Commander Air Group) on US carriers. Although normally there would be only one
Hikotaicho
assigned to a carrier, Genda changed this to as many as three per carrier or as few as none, depending on the plan’s needs.

The B5N Kate units were divided between torpedo bombers and level bombers, two very different skill sets. The late-September start allowed six weeks to resolve problems and train the aircrews for their tasks.