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

by John Geoghegan

  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

  AFTER 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.

  * Accounts vary in the number of survivors killed, ranging from four to eight.

  † Kazuo Takatsuka remembers the two ships sinking on the I-400’s way to Nanao Bay, not Dalian. However, since both Nambu and Sato recall it as happening during the I-400’s trip to Dalian, I’ve done the same.

  ‡ Sato indicates that the original plan was for the subs to mass off the coast of Colombia, which would have put them slightly closer to the Panama Canal. Tsugio Sato, Maboroshi no Sensui Kubo [Phantom Submarine Carrier], (Tokyo: Kabushiki Gaisha Kojin-sha, 1989). However, since Takahashi was at the actual attack plan meeting, it seems more accurate to use his account. Kazuo Takahashi, Shinryu Tokubetsu Kogekitai [Divine Dragon Special Attack Unit] (Tokyo: Koujinsha, 2001).

  CHAPTER 23

  GREEN LIGHT

  WHILE TRAINING CONTINUED, ARIIZUMI 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 Anam
izu, 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.

  Nambu must have swallowed his anger at the rashness of Ariizumi’s plan. He was ready to die in pursuit of the mission, but what was the point of dying before they’d even left Japan? Nevertheless, Nambu instructed the navigator to plot a course for Shimonoseki, and went about his business.

  It was customary for large warships to leave port at night to avoid Allied detection. Since the I-401 was the world’s largest sub, she left that evening under the cover of darkness. When they arrived at Shimonoseki the next day, the view from the bridge reaffirmed Nambu’s concern.

  There were so many sunken ships, their masts looked like a forest of iron trees.17 It seemed impossible that a sub could pass through all that and still avoid a mine. Nambu cut the engine’s RPMs to prevent any sound-activated mines from being triggered and slowly entered the strait.18 Next, he began gingerly weaving his sub through the forest of sunken masts.19 If he could skirt close enough to a wreck, he might be able to hide in its magnetic field and avoid triggering a mine. It was a risky tactic, but the masts would serve as his guide.

  Nambu sweated freely as he navigated the slow-motion slalom course.20 There was nothing more disconcerting than watching a sunken ship slip by, each wreck a testimony to the impossibility of their task. While the I-401 glided quietly on the surface, individual crew members visited the sub’s shrine to ask Ise for protection.21 The snail’s pace of their journey, combined with the visible failure of all those who’d gone before them, only made the crew more nervous. While the lookouts held their breath, Ariizumi remained silent and unreadable.

  Fortunately, Ise watched over them that day. When the I-401 emerged into the Sea of Japan, Nambu felt relief. He was also in for a surprise. There were a shocking number of shipwrecks along the coast22—evidence that enemy mines weren’t just confined to the Inland Sea. The wrecks also suggested U.S. subs might be operating in the area, which would make training a lot more hazardous.

  As the I-401 headed northeast toward Nanao, the attack on the Panama Canal entered its final stage of preparation. Only a few weeks more, and they would be on their way. Nambu’s successful navigation of the Shimonoseki Strait had proved the gods were still on their side. They had come too far not to succeed.

  CHAPTER 24

  FULP’S LAST PATROL

  WHEN THE SEGUNDO’S SECOND WAR PATROL FINISHED, CAPTAIN Fulp headed for Guam. The patrol had been successful—sinking three ships and surviving a flood were no small accomplishments, despite losing a man. Neverthless, when Fulp sailed into Apra Harbor on January 5, 1945,1 Guam came as a relief.

  Fulp released his crew for two weeks of rest and recuperation at Camp Dealey. Dealey had been open only six weeks2 and was still a rude collection of Quonset huts and tents. The Marines had recently recaptured Guam, killing more than 18,000 Japanese in the process. Still, the island wasn’t as quiet as it looked. The United States might have regained control of the shell-cratered speck, but a handful of Japanese remained hiding in the mountains. Some sub crews hunted Japs for pleasure.3 The practice ended in December, however, when five submariners were ambushed and killed.4 The Segundo arrived shortly thereafter, and though most Japanese holdouts had been reduced to carrying spears, Guam was still not secure.

  Ens. Lewis Rodney Johnson learned this the hard way his first night at Dealey. Johnson was fast asleep, about 200 feet from the cook’s tent, when he was awakened by popping noises.5 Jumping out of bed, Johnson was surprised to see Japanese soldiers running past him. The holdouts regularly stole food at night, and the camp’s cooks were chasing them off with rifle fire. Johnson was probably in more danger of being shot by a chef than injured by a hungry Japanese soldier. Still, it was impossible to get a good night’s sleep knowing the enemy was near.

  The problem persisted throughout their stay. One afternoon a Segundo crewman waiting for chow noticed a gap in the line ahead of him. When the crewman took a closer look, he saw a man standing in the gap with no one around him. Realizing it was a Japanese soldier, he gave the man a wide berth. Others in line did the same. The Jap wasn’t a threat, he was just hungry,6 but it was another sign of just how poorly the war was going for Japan. The Japanese soldier was taken into custody shortly afterward, but at least he got a free meal.

  THE SEGUNDO LEFT Guam on February 1, 1945, for her third war patrol. Destined for the East China Sea, she was accompanied by the USS Razorback and USS Sea Cat (SS 399).7 The East China Sea could be dangerous. Known for its shallow water and poor sonar conditions,8 it was a tough place for a sub to hide. Of more concern was the shrinking number of enemy targets. Of the 87 war patrols mounted from Pearl Harbor between January and March 1945, almost 70 percent returned without sinking a single enemy ship.9 In fact, Japanese targets were so scarce, Pacific-based subs were reduced to attacking smaller vessels like fishermen and coastal merchants. If Fulp didn’t know the exact statistics, he certainly knew it was difficult to find the enemy. The Segundo’s third war patrol would be no exception.

  A month went by without Fulp sinking a ship. Aside from the accidental triggering of a fire extinguisher, which “considerably bolstered the boat’s CO2 content,”10 the only other notable event came while the sub was off Nagasaki. Seas were calm, and Ensign Johnson had the watch, when the Segundo’s periscope punctured the waves and spotted an I-boat on the surface. It’s tempting to think the Japanese submarine that Johnson saw was the I-401, since Nambu was conducting shakedown training in the area at this time. We’ll never know for sure because the I-boat turned and headed into Sasebo harbor before Captain Fulp could get off a
shot.11

  Eventually, the three U.S. sub captains became so frustrated at the enemy’s absence, they broke up their wolf pack. They hoped to improve their chances of finding a target by patrolling individually.12 But aside from spotting two Japanese hospital ships, the Segundo continued to lack enemy contact.

  Fulp had already radioed ComSubPac requesting an extension to his patrol when he finally encountered the enemy. It was March 6, and the Segundo was in shallow water off the Korean coast. Normally, Fulp would have let the ship go (she was that small), but they’d been out for a month with nothing to show. He was desperate for action.

  Fulp closed the target to within 1,300 yards before letting loose with four torpedoes. If it was overkill, he wasn’t taking any chances. Incredibly, all four missed. Errors related to the torpedo spread were responsible, which just goes to show what happens when you get the math wrong. Fulp considered a gun attack, but the sea was too rough to be accurate.13 Consequently, the first real target of their patrol escaped without a scratch.

  Fulp’s luck improved the next evening. It was nearly three in the morning when radar identified a target at 16,000 yards. The ship was the Shori Maru, a smallish freighter weighing 3,087 tons. Fulp remained on the surface as he made his approach, despite the sea being so phosphorescent it seemed white. Thirty-six minutes later he launched the first of four torpedoes.

  His lead fish ran erratically, so Fulp aimed for the middle of the target. The second one blew the ship’s stern clean off, while the third struck amidships. It didn’t matter that the fourth went missing because two minutes later the Shori Maru was gone.14

  Fulp intended to pick up survivors but called it off when radar reported a convoy nearby. Two transports accompanied by two destroyers were too juicy a target to pass up. Japanese warships were always more desirable than merchants, and though destroyers were dangerous, Fulp hoped to make a clean sweep of them.