Operation Storm: Japan's Top Secret Submarines and Its Plan to Change the Course of World War II (30 page)

As the
I-401
sat on the bottom of the Inland Sea, Nambu must
have questioned his future. The Imperial Japanese Navy had just experienced a devastating attack, forcing the
I-401
to cower in the waters of her home port. They still had three months of training left, yet the
Sen-toku
squadron had barely survived. It was up to Ariizumi to move things along, but the Allies weren’t going to make it easy. Time was running out.

T
HE
S
EN-TOKU
SUBS WERE LUCKY TO ESCAPE LARGELY UNHARMED
. The
I-400
and
I-401
sustained minor damage; the
I-401
was hit by machine gun bullets,
¹
and the
I-400
’s fuel tank was punctured by shrapnel. Additionally, two crewmen were killed,
²
and Kusaka, the
I-400
’s captain, would need time to recover from his wounds. Surprisingly, the
I-13
had escaped unscathed and the
I-14
hadn’t even been there—once again, Captain Shimizu had been lucky. Taking the
I-14
on a ten-day training mission, he’d departed Kure on March 18, missing the attack by a single day. It was the same fortuitous timing that had saved him from the Kobe air raid.
³
Clearly, Shimizu had good karma.

Takahashi inspected the Kure air base for damage. Empty cartridge casings littered the tarmac, and many of the structures were riddled by cannon fire. The decoy planes were so shot up, they barely resembled aircraft.
⁴
The important thing was that none of the
Seiran
had been damaged. The IJN could hardly afford to lose more
Seiran
with the aircraft in such short supply.

B-29s had already bombed Nagoya.
⁵
The results weren’t quite as spectacular as the Tokyo firebombing the previous day. Still, the incendiaries burned enough of the city that Aichi’s Eitoku facility was damaged, further slowing
Seiran
production.
⁶
Allied air raids and recent IJN losses dealt the Combined Fleet such a devastating blow, it ceased to function as anything more than a self-appointed suicide squad. The U.S. Navy still wasn’t happy with the results though, and B-29s were diverted from bombing cities to parachuting aerial mines into the Inland Sea.
⁷
Operation Starvation commenced on March 27, when nearly a thousand mines were dropped,
many of them in the waters around Kure, where the
Sen-toku
subs were training.

Aerial mining took the IJN by surprise.
⁸
The Kure Naval District did its best to remove them, but there was a shortage of minesweepers.
⁹
Furthermore, the new-model magnetic mines were difficult to dispose of. A training sub hit one mine while practicing off Kure and was lost. The
I-53
hit another and was severely damaged.
¹⁰
Overnight, a significant portion of the Inland Sea became unsuitable for naval operations.
¹¹

Operation Starvation didn’t just curtail IJN fleet movements; it also increased the danger of
Sen-toku
sub training. The
I-400
subs had just begun practicing with their
Seiran
when the mines were laid. Their goal was to assemble, catapult, retrieve, and stow their aircraft with special attention paid to launching them. All three
Seiran
were supposed to be launched in under 30 minutes, but as training began, it took at least 45 minutes to get them into the air.
¹²

Launching three planes in quick succession would be critical to the mission. The longer a sub remained on the surface, the more likely she’d be discovered. But mechanical difficulties hampered a sub’s three
Seiran
from being operational at the same time.
¹³
Even when the planes were working properly, it never lasted; one always broke down.

The situation especially worried Nambu. Only once had the
I-401
managed to launch all three of her aircraft one after the other.
¹⁴
And now that the waters had been mined, it was unlikely they’d get more practice in the Inland Sea.

There was tremendous complexity in launching a
Seiran
. While the sub was still submerged, the plane’s maintenance crew climbed up an access tube that led into the hangar.
¹⁵
Once inside, mechanics pumped coolant and heated lubricating oil into the plane’s engine.
¹⁶
This facilitated a faster launch by reducing the warm-up time a
Seiran
required on the surface. As the maintenance crew prepared the aircraft, another team waited in the conning tower. The minute the sub broke the surface, they dashed on deck to open the giant watertight door leading to where the planes were stored. Once the door was open, the hydraulic whine of the exterior
catapult rails could be heard as they rose to join the rails inside the hangar.
¹⁷

Seiran
were stored sequentially in a sub, nose to tail, with their wings and stabilizers folded. Each plane sat on a rail cart in the hangar. The carts were kept in the lowered position to prevent the plane’s propeller from hitting the ceiling. Before the
Seiran
were wheeled on deck, their bombs were attached.
¹⁸
Once the first two planes were moved out of the hangar, their rail carts were raised, tilting the
Seiran
toward the sky. Finally, a team connected a high-pressure hydraulic hose to begin unfolding the wings.
¹⁹

When Nambu saw how a
Seiran
’s wings were cranked into place, he thought it amazing.
²⁰
Indeed, it was remarkable how elegant the process could be when the aircrew got everything right. But almost nobody got anything right the first few times they launched the planes. Worse, assembly would be a lot more difficult on the wave-tossed ocean than on the relatively calm waters of the Inland Sea. They’d need to practice until everything became second nature.

Hidden mines, maintenance problems, and fumbling aircrews weren’t the only issues, though.
Seiran
flights were becoming increasingly hazardous as the United States began to dominate Japanese skies. Whenever Takahashi and Asamura flew, they had to be on constant lookout for enemy fighters. It was bad enough that the sea was unsafe; now Kure had proven the skies were equally dangerous.

Still, nothing was more hazardous than an inexperienced pilot. A senior pilot like Asamura could execute a smooth-water takeoff after only three attempts, while a junior pilot required at least ten takeoffs to master the practice.
²¹
Takahashi certainly appreciated the junior pilots’ eagerness. But when it came to flying a state-of-the-art aircraft, technical skill outweighed enthusiasm every time.

And then there was mastering dive-bomb techniques. Takahashi didn’t think it would be especially difficult to hit a lock gate since it was stationary, but low-altitude bombing was a skill acquired only after weeks of training. The junior pilots would need lots of it before they’d be effective.
²²

On April 10 ten
Seiran
took to the air over Fukuyama to simulate
attacking the city. After repeated diving from 16,000 feet, Takahashi’s air group finished for the day and headed back to base. Since a storm was coming, Takahashi landed in a river rather than the gulf, where the water was choppy. Two more
Seiran
landed without incident. When it came time for Second Lieutenant Ichiyoshi to put down, he ignored Takahashi’s example and chose the gulf instead. Takahashi held his breath as he watched Ichiyoshi’s plane make its approach.

Boy, that’s dangerous
, he thought.
I’ll have to reprimand him
.

As he watched Ichiyoshi’s
Seiran
bounce across the waves, Takahashi grew increasingly concerned. When one of the plane’s pontoons broke off and the aircraft flipped over, he couldn’t stop himself from shouting, “You idiot!”

A rescue boat rushed to the scene, but Ichiyoshi’s head had smashed into the cockpit windshield, killing him instantly. His observer was luckier. Thrown clear of the plane, he survived the crash.
²³

It was the third accident and fifth fatality for the 631st. Though not unexpected, given the high-risk nature of their training, the casualties were beginning to add up.

A
S IF EARTHQUAKES
, aerial mines, aircraft accidents, and enemy fighters weren’t bad enough, the
Sen-toku
subs soon found themselves out of fuel. Vice Adm. Charles A. Lockwood, commander of the Pacific submarine force, knew Japan’s fuel was running low. His subs had sunk 76 oil tankers with just such a goal in mind.
²⁴
What Lockwood couldn’t have known, was just how little oil was left.

Normally, an I-boat would have enough fuel to spend three months searching for targets. But fuel was now so scarce, Japan’s few remaining subs had to take the most direct route to a shipping lane and wait for something to cross their path.
²⁵
The IJN’s fuel shortage was further compounded when the super-battleship
Yamato
drained the tanks at Kure’s Tokuyama storage depot in April.
²⁶
The
Yamato
was heading to Okinawa to repel the U.S. invasion. Even if she survived the sortie, she would have only enough fuel
for a one-way trip.
²⁷
Some have speculated that the
Yamato
was sacrificed in order to preserve fuel for the
I-401
’s mission.
²⁸
There is no evidence for this claim. The IJN started the war with six million tons of oil,
²⁹
enough to last two years. But Tokuyama, despite being one of the largest oil facilities in the IJN,
³⁰
only had 2,000 tons left.
³¹

The
I-400
and
I-401
each required 1,700 tons of fuel to complete their missions,
³²
and priority was traditionally given to the surface fleet. Attacking the Panama Canal might have been important, but Ariizumi had to compete with the rest of the navy for his fuel allotment. There just wasn’t enough to go around.

The 631st faced similar problems. So little aviation fuel was available that the
Seiran
squads barely had enough for training. Low in octane, the fuel had been blended with turpentine and alcohol to make it go farther, but it was such poor quality, the pilots jokingly called it “Marianas gas.”
³³
The IJN was aware of the problem and planned to use submarine tankers to import two million gallons of fuel from Singapore and Formosa. The
I-402
fell prey to this initiative, along with seven I-class and four HA-class subs. Instead of being completed as an underwater aircraft carrier, the
I-402
was converted into a giant underwater tanker, with a fuel capacity of 182,000 gallons.
³⁴

Given the fuel shortage, Ariizumi faced a difficult choice. Kure had only enough fuel for one
I-400
sub. Without fuel there was no training, no mission, and no hope of staving off defeat. Unfortunately, the Combined Fleet could not give what it didn’t have. Ariizumi would have to go elsewhere.
³⁵

The only place where fuel could still be found in any appreciable quantity was at the IJN naval bases in China and Korea. And so Ariizumi decided to sail his flagship to the port of Dalian in Manchuria to get oil from the stocks located there.

It wasn’t going to be easy. To reach China, the
I-401
would have to sail south through the Inland Sea to one of two exits, the Shimonoseki Strait on Japan’s west coast, which led to the Sea of Japan, or the Bungo Strait on Japan’s east coast, which led to the Pacific. Both exits were heavily mined, and each had its own set of problems. The
Shimonoseki Strait was a ten-mile doglegged channel whose narrowest point was only 800 yards wide. It would be nearly impossible to thread it without encountering a mine. On the other hand, American subs were posted outside the Bungo Strait, just itching to sink any I-boat entering the Pacific.

Ariizumi had no alternative. If he didn’t try for China, he’d never get enough fuel to continue training, let alone embark on his mission. But if he braved the mine-infested waters, there was a good chance he’d never reach China. Ariizumi finally decided on the Shimonoseki route. Yes, it was heavily mined, and there was always the chance the U.S. Navy might attack in the Yellow Sea. Nevertheless, it was the shortest distance between Kure and Dalian. Additionally, the
I-401
had a degaussing mechanism, six cables snaking their way the length of the outer hull. They not only prevented the sub from rusting, they helped shield it from mines by dampening its magnetic field. They would just have to risk it.

Since traveling on the surface was the fastest way to Dalian, Ariizumi had a wooden smokestack added to his flagship to disguise her identity.
³⁶
Given her size, the
I-401
could easily pass for a surface ship. Whether the deception would save her from attack was debatable, but it certainly masked her aircraft-carrying secret.