Operation Storm: Japan's Top Secret Submarines and Its Plan to Change the Course of World War II (3 page)

At first nobody was sure what they were dealing with.
²⁰
No U.S. ships were reported in the area, and it was unlikely to be an enemy vessel this far north.
²¹
There was no mistaking the blip, though, which was sizable and doing 15 knots.
²²
If it was American, fine. But if it was Japanese, they had a problem.

Captain Johnson flew up into the conning tower demanding the target’s range and bearing. Determined to take a closer look, he called for “Tracking Stations.”
²³
When the
Segundo
closed to within 3,000 yards,
²⁴
the dark silhouette materialized into the shape of a gigantic submarine.
²⁵
The sub was so big, it looked like a surface ship. It easily dwarfed the
Segundo
. Since the Allies had nothing remotely close in size, the sub had to be Japanese.

Before Johnson could declare battle stations sparks began flying out of the mysterious sub’s diesel exhaust.
²⁶
Clearly, they’d been spotted. As Johnson scrambled his men, the Japanese sub rabbited into the night at flank speed.
²⁷

Lieutenant Horgan was in the control room plotting the enemy’s course as the chase ensued. Horgan knew fighting was still going on in the Pacific, but he couldn’t understand why a Jap sub would run away. After all, the war had been over for 14 days. Nevertheless, the situation seemed dangerous as hell.
²⁸
Here they were chasing an enemy sub without knowing what they were dealing with. Any way you looked at it, they had a tiger by the tail.
²⁹

As the chase extended into the early morning hours, Johnson pushed the
Segundo
to 20 knots.
³⁰
Every time he tried drawing near, the Japanese sub pulled away. Johnson didn’t trust the enemy not to fire on them, so he settled off their stern quarter at a distance of 4,000 yards.
³¹
He also made sure his torpedo tubes were loaded and ready. If the Jap sub tried anything funny, he’d sink her first.

The
Segundo
’s new captain found himself in an uncomfortable position. Had it not been for the cease-fire, he’d have let go with a spread and sent her to the bottom. But Johnson’s orders prevented him from sinking the sub unless fired upon even though fleeing could be considered a hostile action.
³²
Not surprisingly, he didn’t want to give the enemy that chance.
³³

To complicate matters, he was having trouble reaching his superiors at ComSubPac (Commander, Submarine Force, U.S. Pacific Fleet).
³⁴
At the very least, he wanted to inform them of the situation and request permission to torpedo the sub. The
Segundo
’s captain wasn’t going to play cat and mouse forever, but he was unsuccessful in reaching his command.
³⁵
For the time being, he was on his own.
³⁶

First one hour passed, then another. As the pursuit dragged on, the crew began speculating. No one had expected an unescorted Japanese sub this close to Tokyo, least of all one heading in the opposite direction of the main sub base at Yokosuka. The fact she’d turned tail and run only added to their curiosity.

But as dawn approached, something unusual happened. The enemy sub began slowing. Johnson wasn’t sure what she was up to. Maybe she was ready to surrender, or maybe she was getting into firing position. Fortunately, he’d reached ComSubPac, which advised him to capture the enemy if possible. If they resisted, he was free to sink them.
³⁷

Shortly after four o’clock the morning of August 29, Johnson called QM3c Carlo Carlucci to the bridge. It was Carlucci’s first war patrol. A tough kid from the Bronx whose accent was like a punch in the face, he’d been sleeping when the
Segundo
first spotted the Japanese sub. He was wide awake now though, as he “horsed” the cast iron signal lamp to the
Segundo
’s bridge.
³⁸
Rapidly flicking its shutters, Carlucci pounded out the international code for “stop.”

The enemy sub failed to acknowledge the message even though it was impossible to misunderstand its meaning. The sub may have slowed, but she showed no signs of stopping. Finally, after a few minutes, Carlucci received an affirmative reply.
³⁹
Two minutes later the enemy sub lay dead in the water.
⁴⁰

As dawn slowly illuminated the Japanese sub, Johnson and his men were in for a big surprise. They weren’t facing a typical submarine. It was, in fact, the largest submarine the
Segundo
’s crew had ever seen. Horgan thought she was huge, at least twice as big as the
Segundo
. Carlucci was convinced she was three times as large, and MM (machinist’s mate) Wallace C. Karnes, Jr., could have sworn she was four times bigger. Whatever her actual size, the Japanese sub loomed over the Balao-class boat.

Johnson knew they’d stumbled across something unusual. The enemy sub was big all right, but what he didn’t realize was that he faced the largest submarine in the world, a sub so huge she would remain the largest until the USS
Triton
(SSRN 586) was commissioned in 1959.

Johnson’s men had every reason to feel small. At just over 400 feet in length, the “Jap sub” was longer than a football field. And at 5,223 tons,
⁴¹
her surface displacement was more than three times that of the
Segundo
’s. It wasn’t just her size that made for such a menacing spectacle; the Jap sub also bristled with weaponry. With a 5.5-inch gun on her aft deck; three triple-barrel 25mm antiaircraft guns; and a single 25mm mount on the bridge, the Japanese sub was all business. There were also eight torpedo tubes in her bow, two more than the
Segundo
had, and it was reasonable to assume she carried the deadliest torpedoes of the war: the Type 95,
based on the “Long Lance.”
^†
The Type 95 packed an 891-pound warhead with way more punch than the
Segundo
’s Mark 14s.
⁴²
Johnson wanted to avoid the Japanese torpedoes like the horns of a bull. Not only did they have a third more explosive power than his own torpedoes; they had nearly three times the range and were faster to boot.
⁴³
Whatever the boat’s weaponry, the crew of the
Segundo
had no doubt that they were dealing with a monster sub; a sub that not only dwarfed her in size but was armed to the teeth and whose intentions were painfully unclear.

The boat’s size and weaponry weren’t the only things intimidating the
Segundo
’s crew; the ungainliness of her superstructure also looked nefarious. Her monolithic sail was as high as a three-story building. It should have painted an enormous radar signature, but it appeared to be sitting on an indented base designed to reflect radar waves back into the sea. The most noticeable aspect of the superstructure though was a huge compartment running the length of her deck. The housing was more than 100 feet long and so massive, her sail had to be offset nearly seven feet to starboard to keep the sub from tipping over.

It wasn’t hard to guess what the cavernous structure held, because a catapult stretched from a gigantic, bulbous door toward the bow. This was a plane-carrying sub. But what kind of plane was carried inside such an enormous hangar? The Japanese sub fleet was known to carry scouting planes, biwinged “put-puts” strictly for reconnaissance. This sub was more like an underwater aircraft carrier.

If Captain Johnson felt alarm at the enemy sub’s contradictory behavior, he didn’t show it. But you could never underestimate the
ferocity of the Japanese military even in defeat. If Johnson misjudged the situation even slightly, the
Segundo
was in for trouble. To ensure that didn’t happen, he brought his bow torpedo tubes to bear on his adversary and ordered his helmsman to close the distance.
⁴⁴

As Johnson aimed his binoculars at the Japanese sub a short distance away he could detect nothing wrong with her. In fact, she looked to be in good condition.
⁴⁵
He could make out five figures atop her sail, at least two of which were staring at him through their own binoculars. It appeared to be a Mexican standoff.

By all rights the Japanese sub should surrender. But her decision to flee and her reluctance to stop, especially after being chased, suggested they didn’t intend to give up easily. Yes, they were flying the black surrender flag and her deck guns were pointed downward. Yet nothing else in the sub’s behavior indicated that Johnson should take the flag seriously. After all, she still flew her naval ensign, the
Asahi
, with the red and white rays of the rising empire.

One thing was for sure—nobody in the United States Navy had ever seen a sub like this. For the submarine the
Segundo
now confronted was the
I-401
, the largest, most powerful class of sub built by Japan during World War II. She had been designed for a mission so secretive that the U.S. military didn’t know anything about it, a mission that Admiral Yamamoto, the architect of the attack on Pearl Harbor, had planned himself, a mission so audacious that the Imperial Japanese Navy saw it as a way to change the course of the war in their favor.

As Captain Johnson watched the sub float menacingly in the distance, he carefully considered his options. Depending on what happened next, a resumption of hostilities was likely. If the Japanese refused to follow his orders, he’d have no choice but to blow them out of the water.

What Captain Johnson didn’t appreciate was just how reluctant the
I-401
was to surrender. Not only was the sub part of a top secret squadron of underwater aircraft carriers, it was the flagship that carried the squadron commander, Tatsunosuke Ariizumi.

Commander Ariizumi had been involved with the development
of the
I-400
subs almost from their beginning. Some people considered him their father.
⁴⁶
He certainly knew they’d been designed to attack the U.S. mainland. Why, only a month previously, the planes stored in the sub’s enormous on-deck hangar had been painted to resemble American aircraft, to help slip past U.S. air defenses.

Given her pedigree, the
I-401
wasn’t going to surrender without a fight. In fact, surrendering to the enemy would be more than unacceptable to Commander Ariizumi; it would be an embarrassment and a disgrace. It went against all his years of training as a loyal subject of the emperor and a commander in the Imperial Japanese Navy.

And so, much to their surprise, the men of the USS
Segundo
were about to learn that World War II wasn’t over quite yet because, along with their unproven skipper, they found themselves in what promised to be the last great shooting match of the Pacific war.

L
T
. C
DR
. N
OBUKIYO
N
AMBU STOOD ON THE
I-401
’
S BRIDGE
, squinting through his binoculars at the American submarine 400 yards off their starboard side. He’d done nothing to antagonize the enemy. Nevertheless, the American sub seemed insistent on a showdown.

The
I-401
was one of the last survivors of the Sixth Fleet, the submarine arm of the
Teikoku Kaigun
, the Imperial Japanese Navy. It was a testament to Captain Nambu’s skill, forbearance, and luck that he’d survived this long, especially since his combat career had begun at Pearl Harbor. But the
I-401
was an offensive weapon and Nambu a successful and aggressive skipper. He didn’t like being challenged.

Nambu was fiercely proud of his command. Not only was the
I-401
the world’s largest submarine; she could travel one and a half times around the globe without refueling. She had a top surface speed of 19 knots (six and a half submerged)
¹
and could dive in 56 seconds,
²
no small feat for such a large sub. Finally, she could remain on patrol for 120 days,
³
twice as long as the
Segundo
’s typical voyage.

But the
I-401
’s most unusual feature was her three state-of-the-art special attack planes, carried in her watertight hangar. Purpose-built to bomb New York City and Washington, D.C., the Aichi M6A1 planes were so secret, the Allies didn’t know about them until after the war. This means, the
I-401
wasn’t just a major offensive weapon in a submarine fleet forced to play defense—she was an underwater aircraft carrier designed to hold three of Japan’s
most secret and technologically advanced torpedo bombers, built to attack the U.S. mainland.