Operation Storm: Japan's Top Secret Submarines and Its Plan to Change the Course of World War II (54 page)

T
HOUGH
N
AMBU RECEIVED
“gentle treatment by the U.S. Navy,”
¹¹
Sen-toku
officers faced extensive questioning by naval intelligence. At first investigators wanted to know which ships Nambu had sunk, but they soon zeroed in on who had served in the Indian Ocean. Clearly, the Allies knew about the atrocities and wanted to find out which subs were involved.

Yata, the
I-401
’s chief gunnery officer, was taken to MacArthur’s SCAP headquarters and asked whether Ariizumi had really committed suicide. Yata answered truthfully. Policemen still watched his house, however, hoping the officers they were looking for would show up.
¹²

Two of Ariizumi’s
Sen-toku
captains, the
I-400
’s Kusaka and the
I-14
’s Shimizu, had participated in massacres. The
Sen-toku
crews knew this, so they had something to hide. Since neither Nambu nor Yata had served in the Indian Ocean, they were eventually cleared.
Kusaka, however, didn’t have it so easy. The day after the surrender ceremony, American interrogators descended upon his sub and began calling officers into the wardroom one by one.

An American translator encouraged Takahashi to tell them everything, promising, “We won’t treat you badly.”

Takahashi was hardly going to spill the beans, since he’d massacred prisoners himself. He chose to boast about Ulithi instead.

“It’s a shame the war didn’t last one more day,” he told his interrogators. “If it had, I would have slammed myself into an American aircraft carrier.”
¹³

By the end of September, the U.S. Navy was comfortable enough operating the
I-400
subs that the
Sen-toku
crews were no longer needed. Curiously, none of the subs was ever submerged. Presumably, nobody wanted to risk operating them on anything but the surface.

Before the
Sen-toku
crews were discharged, however, American officials visited them one last time.
¹⁴
In appreciation for their cooperation, they gave the officers 20 cigarettes, a bottle of whiskey, and five ten-dollar bills. The same amount minus the whiskey was given to enlisted men. The gifts were a surprisingly Japanese thing to do—perhaps the American officers had learned something from their former enemies.

Before the translator departed though, he had important information to share.

“You will be released shortly, but the Allied War Crimes Tribunal will begin soon. The massacre of prisoners by submarines is a particular issue. If you are not careful, you may be arrested. Therefore, once you are released, it would be better to lay low.”
¹⁵

The
I-401
’s crew was mustered out of the navy on September 30, 1945.
¹⁶
By that time, the sub had been stricken from the IJN’s roster of active duty ships. After a morning truck ride to a nearby demobilization center, Nambu was promoted one rank and exchanged his summer uniform for a winter one. By noon he was wandering the streets of the city, a free man.
¹⁷

W
HEN THE
U.S. N
AVAL
T
ECHNICAL
M
ISSION TO
J
APAN LANDED
in Yokosuka in September 1945, navy officials were keen to identify the latest Japanese sub technology in case it proved useful. Undersea war experts were already examining Germany’s latest sub, the Type XXI, and though the state-of-the-art U-boat came too late to play a deciding role in the war, it was not too late to incorporate her design into the next generation of American fleet boats. U.S. naval officials already had a pretty good idea which Japanese subs they wanted to study, with the largest and the fastest at the top of their list.
¹
Any submarine that could travel around the world without refueling to launch multiple offensive aircraft against enemy targets was undeniably unique. Not surprisingly, the
Sen-toku
squadron made the short list.

Teams of U.S. experts quickly spread out to the sub bases at Yokosuka, Kure, and Sasebo, where senior Japanese officers were interviewed about Sixth Fleet sub programs. Rear Adm. Katayama, head of submarine design and construction, and Commander Fujimori, the Naval General Staff’s senior submarine officer, were extensively interviewed. Katayama had overseen construction of the
Sen-toku
force while Fujimori was familiar with her top secret operations. Both men spoke freely, helping U.S. intelligence assemble a clearer picture.
²

Not everyone found the
I-400
subs of strategic value; some considered them nothing more than white elephants. One British Royal Navy observer dismissed them as “hopelessly under motored and … the very devil to stop or turn in an emergency.”
³

Though a report issued by the U.S. Navy analyzing the
I-400
subs disparaged the Japanese as pipe fitters, it also noted that this “system will hunt.”
⁴
As a result, all three subs were sailed to Pearl Harbor for further study.

T
HE 4,000-MILE VOYAGE
to Hawaii began in November 1945, when the subs journeyed from Yokosuka to Sasebo. Lieutenant Commander McDowell captained the
I-400
, Cdr. Edward D. Spruance captained the
I-401
, and Cdr. John S. McCain, Jr. (father of the future U.S. senator), commanded the
I-14
. The subs remained in Sasebo for several weeks loading supplies, and in a surprising twist, Hi Cassedy took command of the
I-14
from Jack McCain. Cassedy had been removed from commanding the
I-400
after his run-in with Halsey over Japanese swords. Being a Lockwood disciple, he soon found himself back in favor. And since Cassedy was the most senior officer, he was put in charge of all three subs.

The
I-400
’s prize crew developed their own logo for the voyage. Painted on a pennant, it shows an American sailor with a bulbous red nose riding the
I-400
with reins in one hand, a defeated Japanese soldier in the other. Subtle it was not.

Finally, on December 11, 1945, a minesweeper led the subs out of Sasebo harbor. The USS
Greenlet
(ASR-10) also accompanied the convoy in case one of the boats broke down. When the minesweeper reached the end of the channel, she blinked, “Bon Voyage” instead of the traditional “Good Hunting!”
⁵
Now that the war was over, there was no reason to hunt.

When the
Sen-toku
subs arrived at Guam eight days later, they received a tumultuous welcome. Whistles blew, a brass band played, and navy officials lined up to tour the underwater aircraft carriers. Guam was also jammed with navy surplus. In a cashless economy, it was easily exchanged for Japanese war booty. Soon the subs’ aircraft hangars began filling with luxuries. Japanese rifles were exchanged for prime steaks; a coffee machine and General Electric ice cream maker joined the galley; and a porcelain toilet appeared in the
I-400
’s head. Even individual bunks were wired for music from a jukebox.
⁶

Unfortunately, things didn’t stop there. An irate marine lieutenant stormed aboard the
I-400
demanding that his motor scooter be returned. The chief of the boat assured the executive officer that “nobody is going to find any motor scooter in this boat.”
⁷
The XO knew, however, that that wasn’t the same as saying there was no scooter to be found. Still, the marine was told to take the matter up with his motor pool sergeant. Strangely enough, when the
I-400
sailed for Eniwetok,
⁸
it was the Americans, not the Japanese, that had become pirates.

A brief stop at Eniwetok enabled the
I-14
to repair her engines.
⁹
Unfortunately, the
I-401
’s entrepreneurial crew found themselves in hot water when they were accused of stealing the island commander’s jeep. The sub was searched on the eve of her departure. The missing vehicle never turned up. When the
I-401
was finally granted permission to sail, she was told not to return, or risk being fired upon.
¹⁰

The
Sen-toku
subs arrived at Pearl Harbor on September 6.
¹¹
Cassedy had been informed that his subs shouldn’t appear until dark, to avoid antagonizing Japanese sympathizers.
¹²
Since Cassedy was the highest-ranking officer, the
I-14
would be first to dock,
¹³
followed by the
I-401
and
I-400
. Unfortunately, as the squadron approached the submarine base, a bolt shook loose from the
I-401
’s number-one engine mount. It was no time for screw-ups, but when the
I-401
switched to battery power, her props sped up, and the sub shot past the
I-14
. Cassedy, always first, was fit to be tied.
¹⁴
It didn’t help that a row of admirals and reporters were waiting at the dock.

The next day the local papers were filled with news of the
Sen-toku
squads’ arrival.
¹⁵
The U.S. Navy recognized the publicity value of the subs and wanted to promote them. There was even talk of sailing them up and down the California coast, not to drop biological weapons but to raise money for war bonds. Until then, the subs were put on display at Pearl.

In February the
I-400
went into dry dock. The pungent smell of barnacles rotting in the tropical sun filled the air as sub experts crawled over Kusaka’s former boat. The sub was extensively photographed both inside and out, and her systems were carefully
examined for features that might be incorporated into the design of future American submarines.
¹⁶
A month later, Cdr. R. Kissinger issued a written report summarizing his findings.
¹⁷

Though Kissinger found the sub’s overall construction to be sound and cited several features of interest, he was unimpressed. Curiously, he thought the
I-400
’s hangar carried four aircraft and noted that the sub’s purpose was “primarily for transportation of supplies, fuel, and planes to outlying islands.”
¹⁸
Either Kissinger wasn’t paying attention, or some members of the United States Navy were still in the dark as to her true mission. This discrepancy would be resolved when the U.S. Technical Mission to Japan issued its report. It’s surprising though that six months after the
I-400
’s capture, the nature of her mission was still unclear.

T
HE FATE OF
the
Sen-toku
subs was debated for several weeks.
¹⁹
The
I-400
’s XO, Lt. Thomas O. Paine, argued that the sub should be refitted for submerged operation and further evaluated. As Paine wrote, “I was convinced we should find out how such a huge submarine handled submerged … [and] what lessons her Japanese naval constructors [had] incorporated into her design [as well as] all the other things she could teach us.”
²⁰
Another idea was to convert her into a transport sub.
²¹

Military budgets were in decline, however, and there were no funds for refitting enemy vessels. Paine was told to “stand by and await further orders.”
²²
Though the U.S. Navy was eager to design a new fleet of submarines, it showed little interest in underwater aircraft carriers, particularly in the midst of a demobilization. When it was discovered it would cost three quarters of a million dollars and require six months’ yard work to refit the subs, decision making slowed to a crawl.
²³

On March 26, 1946, Lockwood attended the Submarine Officers’ Conference in Washington, D.C. The
Sen-toku
subs were among the topics of discussion. Kissinger’s report was reviewed, as were findings from the U.S. Naval Technical Mission to Japan. Several of the
I-400
’s “outstanding features” were singled out, including
their sound protective coatings. Nevertheless, U.S. Navy officials found the subs too cumbersome and their number of aircraft too few to be of practical use. As the Technical Mission’s report noted, the
I-400
s had many differences from U.S. submarines, but “there is little of actual technical accomplishment … and few items of possible value to the United States.”
²⁴

It was agreed that no design studies should be made unless the Chief of Naval Operations believed the subs would be required in the future.
²⁵
In other words, U.S. naval officials had no interest in using Yamamoto’s underwater aircraft carriers.

The U.S. Navy might have lost interest, but the Soviets had not. When the Russians learned that the
Sen-toku
subs had been captured, they asked the United States to see them as part of an information-sharing agreement. The last thing U.S. naval officials wanted was the Russian military gaining access to a potentially disruptive technology. Given Soviet interest, U.S. officials denied the Russians access by scuttling Yamamoto’s subs.

In the Japanese version of Scapa Flow, 15 Sixth Fleet subs were slated for destruction. The
I-402
was among the first to go. Early on the morning of April 1, 1946, in an operation called Road’s End, a skeleton crew of Japanese sailors piloted their subs out of Sasebo harbor. One crew fastened cherry blossom sprigs to their sub’s sail; another painted their sail bright green. Escorted by U.S. naval ships, the subs were led 60 miles off shore, where the water was 100 fathoms deep. Once the subs arrived, their crews were removed while demolition experts set explosive charges. Shortly after 1:00
P.M
. the detonations began.
²⁶

The
I-402
avoided that ignominious end, but not for long. Lashed to a second sub, she was used for target practice by the USS
Everett F. Larson
(DD-830). When the two subs stubbornly refused to sink, they were scuttled. Ariizumi must have been rolling in his grave.