Operation Storm: Japan's Top Secret Submarines and Its Plan to Change the Course of World War II (32 page)

Ariizumi was counting on the destructive force of ten
Seiran
payloads to destroy the lock gates. Given the fact that Gatun was the largest manmade lake in the world, he had a good chance for success if his planes got through. If for any reason the
Seiran
didn’t completely destroy the upper lock gates, the massive outward pressure of the lake would finish the job.

After the
Seiran
destroyed the gates, they were to rendezvous with their mother subs in the Gulf of Panama. Ditching their planes in the ocean, the aircrews would swim to their respective subs, climb on board, and return home to Japan.

Several important questions remained, however. One of the biggest was which ordnance to use to destroy the lock gates. Fujimori’s team at the Naval General Staff had researched this question and come to the conclusion that a combination of torpedoes and bombs would be most effective,
³⁷
but more research was required.

After his presentation, Fukunaga opened the floor to questions. Takahashi knew most of the pilots wouldn’t know what to ask, so he was first to raise his hand. Standing as he addressed the 631’s XO, Takahashi asked what phase the moon would be in when the
Seiran
launched from the submarines.

“Out of consideration for the submarines’ safety, you will fly on a moonless night,” came the reply.

Takahashi was taken aback. “Just flying my plane at night with a full tank of gas and a torpedo will be difficult enough. For ten airplanes to find one another in the dark, then fly in formation, will be impossible. What’s more, flying over Colombia at low altitude means the chance of being discovered is extremely high.”

“We’ll look into that and respond,” Fukanaga said dismissively.
³⁸

Takahashi wondered if the attack had been thought through properly. Yes, it was only a draft plan; still, success depended on the details, and Commander Ariizumi was nothing if not detail oriented. Takahashi took some consolation in knowing Ariizumi had listened to his question. The “map exercise” may have ended before the tactical issues were resolved,
³⁹
but at least Ariizumi knew further study was required.
⁴⁰

A
FTER THE ATTACK
briefing, Ariizumi went to Yokosuka Naval Air Base to personally investigate the right ordnance for destroying the lock gates. Once again he confirmed that a combination of torpedoes and bombs was ideal. Unfortunately, a torpedo attack by floatplane bombers required a level of skill that the 631st air group hadn’t yet developed. After discussion, Ariizumi, Fukanaga, and Asamura agreed that all ten
Seiran
planes would carry the largest bomb in the navy’s arsenal, a 1,760-pound behemoth—the same kind that had sunk the USS
Arizona
at Pearl Harbor. They also agreed that the planes would fly at low altitude before slamming into the lock gates. It was the only way to ensure the canal’s destruction, but it meant that none of the
Seiran
pilots would be returning. It was also the opposite of Admiral Yamamoto’s original intention. Yamamoto didn’t believe in sacrificing men unless he had to. Rescuing the
Seiran
aircrew had always been a priority. NGS Staff Officer Fujimori, who had guided development of the
I-400
subs after Yamamoto’s death, shared this view. Given the current level of pilot training, however, the only way to ensure a successful mission was to crash the planes into the lock gates.
⁴¹
And so it was decided, if not explicitly stated, that the Panama Canal attack would become a
tokko
, or suicide mission. It was hardly a surprise given the lamentable state of the war. Now, stakes had been raised to the highest possible level.

Asamura wasn’t afraid of dying. He’d been reconciled to a suicide mission almost from the start.
⁴²
If destroying the canal meant sacrificing 20 men, so be it; Asamura feared failure more than death.
⁴³
He’d stop at nothing to achieve success.

Not everyone shared Asamura’s enthusiasm, especially since the unit wasn’t informed of the change. When a mechanic found a workman tinkering with the
Seiran
bomb release mechanism, he immediately informed Takahashi.

“What are you doing?” Takahashi demanded of the workman.

“I’ve been ordered to fix the
Seiran
so the bombs remain attached to their undercarriage.”

“Do the aircrews know about this?”

The answer was no.

Takahashi immediately went in search of Fukunaga. When he found him, he lit into him with a vengeance: “It’s unforgivable to tell us we aren’t on a suicide mission and then go behind our backs with secret preparations for a
tokko
attack.”

Fukunaga responded coolly, “Given the war situation, airplanes are assigned to
tokko
missions. No air groups can avoid it. All
Seiran
are to participate in a suicide attack.”

“I’m not saying I won’t go on a
tokko
attack,” said Takahashi. “I know planes are flying suicide missions every day. But don’t lie to us. Why can’t you be honest and tell us you want us to go on a suicide mission? That would be the dignified thing to do!”
⁴⁴

Fukunaga was not used to being reprimanded by a subordinate, and he shouted back at Takahashi, “Vice Admiral Onishi decided at an NGS meeting that all
Seiran
will ram the Panama Canal! It was agreed by our unit’s leading officers to keep it secret so as not to stress the aircrews.”
⁴⁵

Surprised at the news, Takahashi turned abruptly and left. Before the day was over, everyone knew the mission had changed.
⁴⁶

Takahashi wasn’t alone in questioning the suicide attack. Nambu was also against it: “I don’t care what Commander Ariizumi or the Sixth Fleet think. As captain, I will find a way to retrieve my
Seiran
crews.”
⁴⁷

Several of the
Sen-toku
captains thought it a waste to send such highly trained pilots on a
tokko
mission. When Takahashi later learned it was Fukunaga who’d insisted on the suicide attack, he became furious all over again.
⁴⁸

The 631st aircrews accepted the decision with equanimity. Nevertheless, their attitudes subtly changed. Some pilots began staying in Fukuyama overnight, even though it was against regulations. Takahashi was one of them. He didn’t care if he was court-martialed. He was going to enjoy what little life he had left. The mission was only a month away. They could hardly afford to dismiss him.
⁴⁹

Training proceeded smoothly despite the discord. The 631st now had ten pilots and ten observers skilled in flying
Seiran
, with additional pilots in reserve. Though engine trouble continued to force emergency landings, the
Seiran
crews were becoming proficient.
⁵⁰
In a few weeks, they’d be ready to attack.

W
HILE TRAINING CONTINUED
, A
RIIZUMI REFINED THE ATTACK
plan. In early May he submitted a draft to Sixth Fleet command who, after reviewing it, forwarded it to the Navy General Staff for approval. It was agreed to launch the
Seiran
on a moonlit night, presumably in deference to Takahashi’s wishes. The upper Gatun lock gates were also confirmed as the target, including the mechanism for opening and closing the doors.
¹
Finally, it was agreed that all ten planes would attack the upper gate one after the other, to ensure its destruction.
²
A mid-June departure date was set for Panama.
³

Squad assignments for all four subs were announced on May 20.
⁴
Asamura was named squadron leader for the
I-401;
Takahashi was put in charge of the
I-400
. The last stage of
Seiran
training involved attacking a full-sized mockup of the Gatun gates. But mining had virtually closed Japan’s Inland Sea, so Ariizumi ordered SubRon 1 and her
Seiran
squads to transfer to Nanao Bay, on Japan’s west coast.
⁵
It was hoped that the sheltered waters of the Noto Peninsula would provide refuge from mines and enemy planes. Attack training could then proceed unhindered.

The
Sen-toku
subs were ready for departure by the end of May. Snorkels had been installed on all four subs, and familiarization training was complete. Since the
I-400
was fully fueled, the
I-401
would get what was left in Kure’s tanks.
⁶
The
I-13
and
I-14
, however, would have to tap the fuel tanks in Chinkai, Korea, before meeting up with their sister subs in Nanao Bay.

The two smaller subs departed on May 27.
⁷
Even the
I-13
and
I-14
were unable to escape the dangers of Shimoneski though. While
the subs overnighted at Moji, a short distance from the strait’s entrance, the port came under attack from B-29s. Both subs got away, but the difficulties were increasing.

The 631st’s four
Seiran
squads flew to Nanao Bay shortly thereafter. The majority of planes transferred to their new base at Anamizu, while a few planes remained at Fukuyama for future missions.
⁸
Once again private homes were rented for accommodations, and weather and communication functions were established.
⁹

The
I-401
prepared to leave for Nanao on June 1, with the
I-400
following the next day.
¹⁰
Many people at Kure Naval Base turned out to see the huge sub off. As a brass band played, officers crowded alongside enlisted men gaping at Ariizumi’s flagship.
¹¹
Asamura must have burned with pride as he watched the dockside gathering. Their mission might have been secret, but he knew what the cheering crowd could only guess at: the
I-401
was Japan’s last best hope for survival. That is, if they got through Shimonoseki first.

The last thing Nambu wanted to do was transit the strait. It was just too dangerous.
¹²
He’d already tried it once and nearly lost his sub. He’d rather take his chances with the Bungo Strait, work his way along the bottom of Kyushu, and then head north. But Ariizumi insisted on the shortcut.

The route seemed reckless to Nambu. Kusaka had just barely managed to get through, and the
I-13
and
I-14
had been attacked not far from its entrance. To make matters worse, Nambu would have to cross the strait at low tide.
¹³
Low tide meant mines were closer to the surface. Since the
I-401
had a 24-foot draft it made her even more vulnerable.
¹⁴
It wasn’t a pretty picture.

Nambu tried persuading his commanding officer to take the Bungo Strait, but Ariizumi insisted the direct route was best. The Bungo Strait had its own problems, he noted. It might have been wider and deeper, but it took longer to navigate than Shimonoseki, and transiting the bottom of Kyushu would leave them open to enemy attack. Plus passing through the Tsushima Strait into the Sea of Japan would be dangerous, since it too was mined. Time was of the essence. They had only a few weeks before the mission; they could afford no further delay. Nambu backed down.
¹⁵

There was often tension between Nambu and his commanding officer. Both men had strong personalities, and both believed their way was best. Part of it was command style, part of it chemistry.
¹⁶
One problem was Ariizumi’s tunnel vision. Rigid and unyielding, he refused to give in. The mission was everything, and he knew best. Nambu, on the other hand, was more flexible. Though the mission was important, the welfare of his crew also mattered. His men might die in battle, but he wasn’t going to sacrifice them needlessly. Ariizumi, however, would destroy the canal no matter what the cost. If men had to be sacrificed, well, that was war. A man’s life was a small thing compared to serving the emperor.