Operation Storm: Japan's Top Secret Submarines and Its Plan to Change the Course of World War II (12 page)

The 17-shi wasn’t the first plane to have folding wings. That honor went to a British aircraft manufacturer in 1913. It wasn’t until World War II that limited space aboard aircraft carriers significantly spurred the development of naval aircraft whose wings folded. It was no easy task, given the complexity of routing multiple fuel, hydraulic, and electric lines through a normally static wing structure, which is why neither the United States nor Japan had folding-wing aircraft at the beginning of the war. Perhaps the closest anyone came to matching Aichi’s wing design was the Grumman F6F Hellcat, and even then there were significant differences.

As NGS officers watched, Aichi’s staff carefully grasped the special attack bomber’s wing and rotated it 90 degrees on its main spar, until the leading edge pointed downward. Then they walked the wing back until it lay flat against the plane’s fuselage. The solution looked simple but was far from it. Aichi had thought of everything, including covering the folding parts of the wing assembly in luminous paint so they could be seen at night when prepping the plane.
⁸

As for the tail assembly, it was decided that both the left and right horizontal stabilizers would fold down at their tip to avoid hitting the sides of the hangar. And since Aichi had selected a propeller 126 inches long,
⁹
there were still six inches of clearance between the prop tip and the hangar bulkhead.

Aichi’s folding method worked so well, it was easy to see how the aircraft would fit within the narrow confines of a sub.
¹⁰
But the NGS had made an important change since the planning stages. The special attack bomber, originally designed for a one-way mission, was now to be reusable.
¹¹
The change made sense. If the bombers could be concentrated against a target, then retrieved and redeployed against other targets, it would greatly increase their destructive capability. There was no point in losing all of them their first time out.

According to various reports, the design spec called for the floats to be jettisonable in midair.
^*
This would increase the plane’s speed and range in case of enemy attack.
¹²
If this feature existed,
it was only at the planning stage though. It was never incorporated into the final design.
¹³

It was clear from the wooden mockup that the special attack bomber was handsome. She was well proportioned, with an attractive shape that looked streamlined. Later, when her air intake was added, she appeared to be grinning.

As Aichi’s prototype made progress, the
I-400
construction program came under attack. A faction inside the Naval General Staff believed the subs were impractical and had become increasingly vocal about it. They argued that the
I-400
subs drew scarce resources from more important shipbuilding programs,
¹⁴
while also claiming the sub’s size made her vulnerable to radar.

Every bureaucracy has its infighters. The chief opponent in this case was the NGS staff officer Cdr. Shojiro Iura. The man who’d briefed Fujita on burning Oregon forests wanted the
I-400
program reduced to two subs that targeted commercial shipping. “It would be different if they could have been finished right after the war started,” Iura argued, “but the plans have only just been completed. It will take at least two years to build the subs. Even their planes have just begun testing.… They cannot be relied upon to have a substantial impact.”
¹⁵

It was a radical departure from Yamamoto’s vision, and Iura was not alone. Several sub captains were also against the
I-400
s. They believed launching and retrieving sub-based aircraft in a combat zone was tantamount to “suicide.”
¹⁶
Calls to scale back or cancel the program only increased.

Perhaps the most compelling argument for killing the program was the Battle of Midway. After Midway Japan increasingly fought a defensive war, and as the Japanese Empire focused on protecting its perimeter, there was less need for large-scale submarines to attack the U.S. mainland. Had the subs been completed shortly after Pearl Harbor, everything might have been all right. But the subs were at least a year from being finished. Time was running out.

Iura represented a formidable rear guard. But sometimes it’s more dangerous to kill a project than to leave it alone. When it was suggested to Ariki Katayama that they stop production, the man
responsible for building I-boats cunningly replied: “It may not be possible.… Material for four
I-400
subs has already been ordered and preparations are under way.”
¹⁷

It was a classically Japanese way of skirting the issue, no less effective for being indirect. After all, the
I-400
squadron was Yamamoto’s idea, and though his recent spate of losses had humbled him, he was still commander in chief of the Combined Fleet. That is, until the United States miliary decided to kill him.

Yamamoto was on the island of New Britain preparing to fly from Rabaul to Bougainville when the United States made its move. It was a few minutes before six
A.M.
, April 18, 1943, just two weeks after Yamamoto’s fifty-ninth birthday. The morning was sunny and hot as his Mitsubishi twin-engine bomber lifted off the runway into the clear blue sky. Bougainville was only an hour and a half from Rabaul, yet Yamamoto’s plane and an accompanying “Betty” bomber were escorted by six Zero fighters in case of enemy attack.

What Yamamoto didn’t know was that U.S. cryptographers had broken the Japanese naval code and knew in advance exactly where he was going. Eager for revenge, 18 P-38s were sent to shoot down the architect of the Pearl Harbor attack. Yamamoto flew straight into an ambush.

The death of the Combined Fleet’s commander in chief had devastating consequences. Talent was thin at the top of the Imperial Japanese Navy; replacing him would not be easy.
¹⁸
Importantly, everything Yamamoto had worked on was thrown into doubt, including the
I-400
program. It wasn’t long before reactionary forces had their knives out. Now that Yamamoto was dead, they would have their day in the sun.

T
HE
C
OMBINED
F
LEET WAS SEVERELY SHAKEN BY THE DEATH OF
its commander in chief. Yamamoto may have had mixed success, but nobody expected him to be carried off the battlefield. The Japanese public wasn’t informed of his death until more than a month after it happened. When it finally was announced, Yamamoto was awarded the Order of the Chrysanthemum First Class and posthumously promoted to fleet admiral. Still, it was just papering over the loss.

Rear Admiral Yamaguchi was supposed to succeed Yamamoto. But when he lashed himself to his sinking carrier at Midway, the IJN lost a competent replacement.
¹
Adm. Mineichi Koga, Yamamoto’s actual successor, was capable of bold thinking, but switching quarterbacks in midgame is tricky, especially when supporting players have trouble handling change.

Interestingly, the IJN didn’t make a connection between Yamamoto’s plane being shot down and the U.S. ability to read their naval codes. In fact, the Naval High Command believed it was impossible. Their stubborn refusal to believe that their codes had been compromised blinded them to what many sub captains already suspected. It would prove a crucial error.

Yamamoto had been dead less than a month when the jackals inside the NGS made their move. One of the
I-400
’s most powerful opponents was Shigeyoshi Miwa, chief of the Seventh Division, which had recently been created to oversee all aspects of IJN submarines.
²
Miwa had never liked the
I-400
s and was well positioned to kill the program.
³
There were other factors working against the
I-400
s as well. The Allied advance had so tightened
the noose that by mid-1943 steel shipments were in sharp decline. It was senior NGS naysayers who most hurt the program though. They were against the underwater aircraft carriers on principle, and with Yamamoto gone, they cut back the number of subs from 18 to 10.
⁴

Kurojima, Yamamoto’s confidant, was determined not to give up the fight. After the death of his mentor, he had been moved to the NGS as Second Division chief. This meant the “weirdo officer” was ideally placed to defend Yamamoto’s wishes. Like any good bureaucrat, Kurojima wanted to test the waters before deciding what to do, so he sent his staff officer, Lt. Cdr. Yasuo Fujimori, to investigate.

Fujimori was a good choice to gather intelligence since his job allowed him to move freely among the various NGS factions. Taking his role to heart, Fujimori set about convincing Miwa to support the program. But Fujimori faced an uphill battle. Twice he tried persuading Miwa, and both times he failed to change the stubborn officer’s mind. The second time Miwa got so angry, he told Fujimori never to bring the subject up again.
⁵

It’s unlikely that Kurojima was surprised by Fujimori’s failure. Miwa had never kept his feelings secret, and besides, Kurojima was only feeling him out before confronting the man himself. Fortunately, Kurojima had another card up his sleeve. When Fujimori reported his failure, Kurojima played his hand.

“Immediately following the start of war, Yamamoto told us we must reach the U.S. mainland,” Kurojima explained. “This is why he ordered large-scale submarines that carry attack planes. [Given the war has changed,] we should now investigate how these can best be used to immediately revive their construction.”
⁶

Kurojima directed Fujimori to prepare a report on the number and types of submarines in the Sixth Fleet stable. This was a sound approach, given that most NGS officers agreed that too many different subs were being built. As one IJN officer observed, a Sixth Fleet shipyard was “like an exhibit at a submarine trade fair.”
⁷
But knowing what to do and persuading a bureaucracy to do it are two different things.

It didn’t take Fujimori long to demonstrate that the wide variety of Sixth Fleet subs hindered production efficiencies. The U.S. Navy had already consolidated sub design to realize the benefits of high-volume sub production. As a result, it was turning out high-quality, state-of-the-art subs before the war had even begun. But there were so many variations on Japan’s
Kirai-, Kaidai-
, and
Junsen
-class subs, it was almost impossible to keep track.

Fujimori’s analysis also revealed several important findings. First, enemy radar was responsible for the loss of many Sixth Fleet subs. Since Japan lagged in radar development, the imbalance wouldn’t be corrected soon. This meant the Sixth Fleet needed to rethink how it used submarines, since its current strategy would only result in further casualties.

The Allied advance also necessitated a strategic rethink. Sixth Fleet sub requirements had changed since Pearl Harbor. They were no longer conducting war patrols off the American coast. In fact, they’d pulled so far back, they were at risk of losing control of the South Pacific. As the United States captured more territory, Japan was also having trouble resupplying army garrisons stranded on remote island outposts. Cargo subs were needed so that those currently engaged in underwater transport could be redeployed to fight the enemy.

Fujimori also acknowledged that the war in Europe had turned against the Axis. If Germany eventually lost, the Allies would redeploy their resources against Japan. It was a discomfiting thought. The U.S. Pacific Fleet was easily replenished, given America’s production capacity. In comparison, Japan could ill afford to waste her limited resources. The Sixth Fleet had to fight smarter if it was going to survive.

Fujimori’s analysis was as prescient as it was reality-based. Sixth Fleet sub production clearly needed to be consolidated, and it’s to Fujimori’s credit that he was so honest in the face of a bureaucracy not used to hearing the truth.

Fujimori’s first recommendation was to focus production on three new types of subs. The first would be a state-of-the-art boat capable of achieving underwater speeds of 18 to 20 knots. These
speeds were so fast, they were usually associated with surface travel, yet Fujimori had investigated the matter and believed a technical solution was possible.

He also called for the construction of dedicated cargo subs that could be used to transport supplies to areas where the surface fleet couldn’t go. The number of combat subs currently being used in resupply operations was not only a poor use of their capability; it drove a high attrition rate. In other words, captaining a cargo sub was rapidly becoming a suicide mission.

Finally, Fujimori recommended that all 18 of the underwater aircraft carriers be built and that their construction be given the highest priority. “When striking a blow against a colossus like America, surprise attacks at vital locations are most effective,” he wrote. “The
I-400
is the best [weapon] in the present arsenal for doing this.”
⁸

But Fujimori didn’t stop there. He went on to argue for an increase in the
I-400
’s striking power to get America’s attention. Specifically, he recommended enlarging the
I-400
’s deck hangar to house not just two but three special attack bombers. He also requested that the
I-13
and
I-14
hangar space be increased to include a second plane.
^*

Fujimori persuaded Ariki Katayama to finish the first two
I-400
subs plus the
I-13
and
I-14
within ten months,
⁹
less than half the time normally required to build a new submarine. Katayama felt it was possible if the project was made a top priority. Cancellation of the three remaining AM type subs originally planned (5094 to 5096) may have helped, but construction of the
I-1
and
I-15
would take longer.