Approval was only momentary, however. In a March 26 meeting to discuss the operation, one of the army’s most senior officers, Yoshijiro Umezu, chief of the Imperial Japanese Army General Staff, rejected the plan.
“The operation is unpardonable on humanitarian grounds,” Umezu declared. “If a virus is used, war between Japan and the U.S. will escalate to war against all humanity and Japan will be the subject of derision.”29
Naval authorities opposed Umezu’s decision,30 but once the army had withdrawn its support, there was nothing they could do. Operation PX was killed before the Sen-toku squadron was any the wiser.
Given their respective historical roles, it’s ironic that the Imperial Japanese Navy proposed such an Armageddon-like attack while the army counseled restraint. Obviously, fighting had become so desperate there was nothing Japan wouldn’t do to prevent defeat. Though the navy had its share of harebrained schemes, including swimming tanks; human torpedoes; rocket-powered suicide planes; and some might even add the Sen-toku subs, the navy usually took a conservative path. But by 1945, Japan’s strategy of choice was to mobilize every means possible to resist surrender. If this meant organizing suicide attacks by kamikaze and kaiten, or training women and children to use bamboo spears to repel an Allied invasion, so be it. Operation PX fit right into this mindset.
BY THE START of 1945, the Sixth Fleet was a shadow of its former self. Only 20 modern combat subs were left, including the Sen-toku squadron. Many of the remaining subs were being refitted to carry kaiten, which meant combat subs were no longer considered offensive weapons as much as transport vessels for suicide torpedoes. Add to this a few surviving cargo subs and obsolete boats suitable only for training, and the Sixth Fleet was virtually extinct.31
Nambu’s former command, the I-362, soon joined the list. The cargo-carrying sub had been scheduled to arrive at Mereyon Island on January 21. When she was reported missing, Nambu had no choice but to mourn his comrades.32 And the I-362 wasn’t the only sub missing. Ariizumi’s Indian Ocean boat, the I-8, had been lost as well. The I-8 had been pursuing an American convoy on the surface southeast of Okinawa33 when a lookout sighted the USS Stockton (DD-646). Part of the convoy’s screen, the U.S. destroyer tried contacting the Japanese sub using a megaphone.34 Ariizumi’s replacement, Lt. Cdr. Shigeo Shinohara, had no interest in listening, and ordered a crash dive.
As the I-8 approached the 100-foot mark, depth charges began exploding near her stern.35 Since the Stockton easily determined the sub’s position from the sound of her propellers, the accuracy of the attacks improved and their frequency increased. Minutes later a depth charge exploded, holing the crew’s quarters, and water began flooding the compartment. The sudden loss of buoyancy forced the sub down near the 450-foot mark, dangerously close to crush depth. The cascading seawater concentrated in the sub’s stern exacerbated her plunge and tipped her bow upward at a 25-degree angle.36 It was like climbing the Matterhorn for anyone inside.
The crew did their best to make repairs, but the sub’s main power plant was offline, and the concentration of water in the stern meant the sub continued to sink. The only thing Shinohara could do was give the order to blow the after tanks. Though this stopped the sub from imploding, the air bubbles betrayed her position, causing the Stockton to send down another wave of depth charges.37
The attack lasted four hours. All the I-8’s crew could do was silently await death.38 The Stockton made seven attacks in all. When her depth charges were exhausted, she was joined by the USS Morrison (DD-560), which dropped 11 more patterns.39 Finally, Captain Shinohara gave the order for battle surface. It was a brave if desperate move, because the I-8 had no more torpedoes left with which to defend herself.40 The only thing Shinohara could count on was darkness. After the I-8 blew her tanks, another mass of bubbles rushed to the surface, marking her location. When she broke the waves at 2:00 A.M., the enemy was waiting.
The I-8’s gun crew crowded into the conning tower while the sub cleared the waves. The moment the bridge hatch opened, the men sprang into action. There was a strong wind and a big swell as Petty Officer Takamasa Mukai ran barefoot to his station. The moon hung in the sky like a pale searchlight while Mukai loaded the 140mm gun.41
The Morrison was only 900 yards away when the I-8 surfaced. The destroyer spotted the sub off her starboard bow and immediately tried to ram her.42 The I-8’s 25mm antiaircraft gun was first to open up.43 Mukai also got a round off before enemy gunfire began smacking into the deck around him.44 A moment later a metal splinter pierced his foot.
Mukai ran to the bridge for help, but just as he approached, one of the enemy’s five-inch shells blew it apart.45 Stumbling back to his post, he resolved to make a stand. The two destroyers pounded the sub for half an hour.46 Finally, after multiple hits47 the I-8 rolled over48 and went down by the stern. Mukai was thrown into the ocean. When he awoke, he found himself in the sick bay of an American destroyer,49 the only I-8 crewman to survive.
These were but two examples of the fate that awaited the fast-dwindling number of Sixth Fleet submarines. Lost sub commands, inexperienced flight officers, harsh water landings, and sandy hydraulic fluid were only some of the problems bedeviling the Sen-toku subs. Vice Adm. Marc A. Mitscher was about to significantly add to them. This time it was Kure’s turn to feel the pain.
KURE WAS A navy town. The IJN had been there more than a hundred years, bringing a measure of culture and sophistication to what otherwise would have been a sleepy little fishing village. Now one of Japan’s “big eight” cities, Kure was home to approximately half a million people, many of them connected with the IJN. Navy paychecks had enabled music, theater, and the tea ceremony to flourish, in addition to bringing running water and flush toilets to the city.50 The most important aspect about Kure was that it was home base to the principal units of the Japanese fleet. This made it a tempting target for Vice Adm. Marc A. Mitscher’s Task Force 58. Suddenly, it was payback time for all those islands America had wrested from Japan.
The I-400, I-401, and I-13 were anchored at the Kure Naval Base when dawn broke the morning of Monday, March 19. The I-401’s crew had just returned from a five-day pass. Chin-Ji Inouye, the I-401’s sonar operator, was eating breakfast and thinking about his family when the air raid sounded. Sprinting to the I-401, he took up a defensive position alongside his crewmates. Time stood still as they craned their necks toward the empty sky. As sirens wailed in the background, they nervously awaited the arrival of the enemy air armada.51
Satoru Fukuoka, a Seiran ground crew member, was carrying ammo to an antiaircraft battery halfway up a mountainside when American aircraft first appeared. As he watched the enemy’s attack leader dip his wing, Fukuoka prepared for the worst. One Grumman Hellcat after another swooped down in a power dive and, leveling out a few feet above the naval base, opened up with their 20mm cannons. The effect was devastating.52
Fukuoka’s AA battery found it difficult to shoot down the enemy planes. The mountains shielded the aircraft until the last possible moment, and once their power dive began, it was too late.
Lt. Tsugio Yata, the I-401’s 22-year-old chief gunnery officer, had joined the sub just before her commissioning. An Etajima graduate, Yata was young and energetic but had never experienced battle.53 The attack happened so quickly, he had little time to organize the I-401’s defenses. As Helldivers and Corsairs began diving out of the sky, Nambu guided his gunnery officer: “Wait, wait, not yet, gunnery chief.” Then: “Now Teppo! Shoot!”54
The roar of the I-401’s triple-mount antiaircraft guns was so great, Yata couldn’t hear his own commands. His gun crew discharged at least 10,000 rounds defending their sub, but the enemy planes were so thick, it was like shooting a swarm of bees.55
The I-400 was nearby in number-two dry dock and unable to move.56 The crew had been warned of the attack, so her guns were manned and ready when the first planes appeared57 at 7:30 A.M.58 Though trapped, she put up a good fight. Koshimoto, one of her many engineers, lugged a
mmo as fast as the gun crew could expend it.59 Brass casings piled on deck like New Year’s confetti, their delicate clinking lost in the cacophony.60 One enemy aircraft scribbled a smoke trail across the sky before exploding in midair.61 Another lost a wing and turned upside down before crashing nearby.62 Although a few planes were shot down, it was the IJN that took a beating that day. U.S. aircraft were targeting four battleships anchored in the harbor:63 the Yamato, Ise, Haruna, and Hyuga.64 Normally, a battleship would try to escape an air attack, but that wasn’t possible in this situation—their fuel tanks were empty.65 Nevertheless, the battleships fought back with everything they had. Turning their cannons skyward, they blasted away with tremendous force.66 Though the sound was deafening and the fury impressive, it was a waste of ammunition. The nimble attack bombers could easily evade cannon fire.
Inouye felt as if every antiaircraft weapon, machine gun, and sidearm was being used to repel the attack, but from Takahashi’s position atop Yashiro Island, the air base seemed unable to defend itself.67 Takahashi had been in Kure that morning. When he heard that carrier-based aircraft were heading their way, he jumped in his Seiran and flew it to the island for safety.68
Takahashi watched awestruck as enemy planes turned aircraft hangars into sieves. It was dispiriting.69 The real battle wasn’t taking place on the airfield though—it was happening in port. U.S. naval intelligence may not have known about the I-400’s mission, but it was hard to miss three gigantic submarines anchored in the harbor.
As wave after wave of enemy planes descended, Nambu hurried to get the I-401 under way.70 Meanwhile, huge water geysers erupted nearby as the sub pulled away from the pier. Yata had no doubt they’d been spotted and were now the focus of attack.71 Though the sub’s triple-mount batteries chased the enemy across the sky, it was pointless to remain. The I-401 had put up a good fight, but she was being raked by machine-gun fire, and enemy bombs were closing in. The I-400 might have been stuck in dry dock, but the I-13 had already escaped. Nambu had to follow.
The I-401 was fueled, so all Nambu had to do was find deep water and submerge.72 But as the sub backed away from the dock, an enemy plane released a bomb overhead. Inouye watched it tumble toward the sub as if in slow motion. He could feel in his bones it was going to hit them.73 But instead of striking the I-401, the bomb landed on the pier next to them.74 The explosion was only 100 feet away,75 so Inouye was close enough to see a gunner on the I-400 get his face blown off. It only took a second, but the image burned into his brain forever.76 Captain Kusaka was also injured, hit by shrapnel in the head and thigh,77 as was the I-400’s chief navigator. By the time the explosion dissipated, at least six men were dead, two of them Sen-toku crew members.
So much smoke blanketed Kure that Nambu used it as cover.78 It was still a shock though when he passed the Oyodo. Rolled onto her side, her decks awash, the cruiser’s guns were blazing into the sky. Her fighting spirit made Nambu proud.79 Nevertheless, as soon as the I-401 cleared the harbor, he submerged to periscope depth and waited out the rest of the attack underwater.
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.
* Dates for the I-14 departing Kobe vary. For example, Nambu recalls the I-14 “being completed” on March 10, 1945; see Nambu, Beikidoukantai wo Kishuseyo, p. 206. Tsugio Yata and Tsugio Sato both say the I-14 departed Kobe on March 14, or the day before the Allies launched a B-29 raid against the city. See Sato, Maboroshi no Sensui Kubo, p. 147. The U.S. Naval Technical Mission to Japan, Reports of the U.S. Naval Technical Mission to Japan, Series S: Ship and Related Targets, Index no. S-17, Japanese Submarine Operations (Washington, D.C.: Operational Archives, U.S. Navy History Division, 1946), chap. 2, states that the I-14 departed Kobe on March 14. However, if the I-14 left Kobe the day before the Allied bombing raid, it must have left on March 16, since the raid took place on March 17.
CHAPTER 21
ADVERSITY
THE SEN-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 stabiliz
ers 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
Operation Storm: Japan's Top Secret Submarines and Its Plan to Change the Course of World War II Page 20