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

by John Geoghegan

  Heading east, Fujita flew a few more miles before dropping his second bomb. Satisfied he’d made an important contribution to the war effort,40 he leveled off at 100 feet and pushed his plane as fast as she could go.41

  Fujita planned to rendezvous with the I-25 at sea. However, as he passed Cape Blanco, he spotted two merchant ships directly in his path. Fujita didn’t want the ships alerting American air defense, but he didn’t have much choice. If he was going to meet the I-25 at the predetermined location, he had to pass the two ships. The question was how to do it without being identified?42

  The only answer was to fly between the ships at such low altitude, they wouldn’t spot the insignia on his wings. His seaplane’s silhouette was also a problem though, so Fujita flew so close to the wave tops that his floats nearly skimmed the water.

  Unfortunately, his observer miscalculated their location. As soon as they were over the horizon, they realized they were too far south. Informed of the mistake, Fujita backtracked. Air defense officials were looking for him by now, so it soon became a race to see whether Fujita found his sub first, or U.S. fighter planes found him.

  Fortunately for Fujita, he found his sub. After spotting the I-25, he executed a prearranged series of maneuvers like a scout bee signaling he was friendly.43 When it was clear he’d been identified, he landed the plane, taxied alongside the sub, and was craned aboard.

  Protocol dictates that officers behave in a calm manner when reporting to a superior, but Fujita could hardly restrain himself when he saw Captain Tagami. “Mission complete, sir. Both bombs exploded. Two large fires are spreading.”

  What excited Tagami more though was Fujita’s news that two merchant ships were heading north at 12 knots. “Give me a course to intercept those ships!”44

  As far at Captain Tagami was concerned, the I-25 was still an offensive weapon, even if he’d just launched the first sub-borne airplane attack of World War II.

  The technicians were still disassembling Fujita’s plane when Tagami gave the order to pursue the freighters. Fujita was impressed by his captain’s aggressiveness: attacking two ships after launching the first air raid on American soil demonstrated the proper fighting spirit. But the I-25 was no match for U.S. air defenses. An American plane dove out of the sky and dropped two bombs on the sub just moments after the flight crew secured her hangar door.† Fujita had led the Americans right to the sub.

  The I-25 dove, leveled off at 250 feet, and rigged for silent running. As the crew listened to depth charges exploding overhead, it soon became apparent the detonations were moving farther away. Jokes were made about the accuracy of American fliers. An enemy had to be perfect to impress a Sixth Fleet crew.45 Clearly, these were not.

  The I-25 remained submerged that day. Later in the evening when things were quiet, Tagami surfaced to recharge their batteries. Fujita was anxious to discuss the next attack, since they still had four incendiaries left. He was curious what the captain would do. Both men had recently heard an American radio broadcast describing the Japanese as capable only of repetitive behavior.

  “The Americans will be expecting another sunrise [attack] … in the usual Japanese manner,” Tagami said. “We’ll make the next one a night attack [instead].”46

  Fujita smiled at his captain’s humor.

  The I-25 may have become the most wanted submarine on the west coast, but that didn’t stop Tagami from attacking an American freighter.‡ 47 Fujita was anxious to make his next flight, of course. The plan was to launch off Cape Mendocino and torch California’s redwood forests. When seas proved too rough, Tagami returned to the scene of their first attack. Maybe the Americans wouldn’t expect him after all.48

  The I-25 surfaced 50 miles west of Cape Blanco at midnight, September 29, 1942.49 By now, the Oregon coast was blacked out, but a full moon helped guide Fujita into the sky. Once again he used the lighthouse to navigate and flew inland for half an hour before releasing his incendiaries into the old-growth forest below. Satisfied each bomb had exploded, Fujita turned round and headed back to the sub.§

  Taking no chances on his return trip, Fujita passed north of Cape Blanco to avoid being spotted. He also cut power as he approached the coast and began a long, silent glide that took him over the ocean. Following a predetermined route, he flew west until he reached the rendezvous point. Unfortunately, the I-25 wasn’t there.50

  Fujita knew the risks. The sub came first, his floatplane second. Though it was possible his observer had miscalculated, it was equally possible the I-25 had been spotted and forced to submerge. Something similar had happened with the I-36’s floatplane. After flying over Pearl Harbor to report on damage, the aircraft hadn’t been able to return without betraying the I-36’s position. The plane and her crew were never heard from again.51

  Fujita banked steeply to get a clear look at the ocean. Locating a sub was like finding a particular feather in a barnyard, and it was even more difficult when it was dark. Though moonlight helped Fujita to see for miles, there was no sign of the I-25.

  Fujita was willing to die on behalf of his country, but he wanted his death to mean something. To crash into an enemy ship was honorable. Even diving into the Cape Blanco lighthouse was acceptable so long as the enemy was hurt. But to run out of fuel and crash into the sea was a waste.52 Time was running out, however. Unless they found the I-25, they’d quickly run out of options.

  Ironically, the thing that saved Fujita was the same thing that could have caused the I-25 to be sunk: the sub was leaking oil. Much to his relief, Fujita spotted an iridescent slick on the ocean and followed the trail until it led him to the I-25. Then he landed alongside the sub and was craned back on board.

  Fujita’s two attacks were front-page news in Japan. The Asahi Shimbun, one of the country’s largest-circulation newspapers, plastered the story in celebratory headlines:

  INCENDIARY BOMB DROPPED ON OREGON STATE

  FIRST AIR RAID ON MAINLAND AMERICA

  BIG SHOCK TO AMERICANS53

  Poor weather prevented Fujita from a third attack. Fortunately, it wasn’t necessary—he’d accomplished his objective. Though unseasonably heavy rains dampened the forests enough to prevent Fujita’s fires from spreading, fear was rampant on America’s west coast. If this was the kind of reaction a few bombs could provoke, imagine what would happen when the I-400s launched their attack on New York and Washington. That had been Yamamoto’s plan all along. They just needed time to execute it.

  * As we know from Nambu’s memoir, this intelligence was faulty.

  † This is how Fujita remembers it. Other Japanese accounts say the plane attacked the I-25 the next day.

  ‡ The SS Commercial Trader was sunk on this date, but records indicate it was sunk not by the I-25 as claimed but by the U-558, 75 miles east of Trinidad. Most likely, the I-25 sunk a different freighter.

  § The U.S. Forest Service has no record of any fires in this area on this date. As a result, it’s assumed that the bombs malfunctioned, or else, as in the previous raid, the unusually wet forest prevented a blaze from starting. However, unlike the first two incendiaries, no traces of these two bombs have ever been found. They’re still out there somewhere.

  CHAPTER 7

  CHALLENGES

  CONSTRUCTION ON THE FIRST THREE SEN-TOKU SUBS BEGAN IN early 1943. The I-400’s keel was laid first on January 18 at the Kure naval arsenal, the I-13 followed less than a month later in Kobe, and construction was set for April on the I-401 at Sasebo.1

  The I-13 was the second-largest sub built by the Japanese Navy. Based on a modified version of the I-9 sub, the I-13 AM (for Type A Modified) was only 28 feet shorter than the I-400 class.2 Originally planned to carry only one aircraft in comparison with her larger sister, which carried two, the AM subs were hindered by a limited cruising range. Since the route from Japan to New York would pass either Africa’s Cape of Good Hope or South America’s Cape Horn, the I-13 would have to be refueled by one of the I-400s during her return trip.3 Seven AM Type subs were p
lanned (I-1, I-13 through I-15,4 and 5094 through 50965), along with 18 of the I-400 class. Once their special attack bombers were included, the Sen-toku squad promised to cause significantly more damage than Fujita’s lone plane over Oregon.

  While sub construction was under way, Aichi made progress on the special attack plane. Nineteen forty-two was devoted to basic research,6 with attention paid to wings and tail assembly. By January 1943 Aichi was ready to demonstrate the complex task of folding the plane’s wings.

  Aichi’s skunkworks were located in a cold, cavernous hangar at its manufacturing plant in Nagoya. A select gathering of Naval General Staff officers were invited to tour a wooden mockup.7 As the NGS officers gathered around the full-size model, they marveled at Aichi’s engineering solution.

  The 17-shi wasn’t the first plane to have folding wings. That honor went to a British aircraft manufacturer in 1913. It wasn’t until World War II that limited space aboard aircraft carriers significantly spurred the development of naval aircraft whose wings folded. It was no easy task, given the complexity of routing multiple fuel, hydraulic, and electric lines through a normally static wing structure, which is why neither the United States nor Japan had folding-wing aircraft at the beginning of the war. Perhaps the closest anyone came to matching Aichi’s wing design was the Grumman F6F Hellcat, and even then there were significant differences.

  As NGS officers watched, Aichi’s staff carefully grasped the special attack bomber’s wing and rotated it 90 degrees on its main spar, until the leading edge pointed downward. Then they walked the wing back until it lay flat against the plane’s fuselage. The solution looked simple but was far from it. Aichi had thought of everything, including covering the folding parts of the wing assembly in luminous paint so they could be seen at night when prepping the plane.8

  As for the tail assembly, it was decided that both the left and right horizontal stabilizers would fold down at their tip to avoid hitting the sides of the hangar. And since Aichi had selected a propeller 126 inches long,9 there were still six inches of clearance between the prop tip and the hangar bulkhead.

  Aichi’s folding method worked so well, it was easy to see how the aircraft would fit within the narrow confines of a sub.10 But the NGS had made an important change since the planning stages. The special attack bomber, originally designed for a one-way mission, was now to be reusable.11 The change made sense. If the bombers could be concentrated against a target, then retrieved and redeployed against other targets, it would greatly increase their destructive capability. There was no point in losing all of them their first time out.

  According to various reports, the design spec called for the floats to be jettisonable in midair.* This would increase the plane’s speed and range in case of enemy attack.12 If this feature existed, it was only at the planning stage though. It was never incorporated into the final design.13

  It was clear from the wooden mockup that the special attack bomber was handsome. She was well proportioned, with an attractive shape that looked streamlined. Later, when her air intake was added, she appeared to be grinning.

  As Aichi’s prototype made progress, the I-400 construction program came under attack. A faction inside the Naval General Staff believed the subs were impractical and had become increasingly vocal about it. They argued that the I-400 subs drew scarce resources from more important shipbuilding programs,14 while also claiming the sub’s size made her vulnerable to radar.

  Every bureaucracy has its infighters. The chief opponent in this case was the NGS staff officer Cdr. Shojiro Iura. The man who’d briefed Fujita on burning Oregon forests wanted the I-400 program reduced to two subs that targeted commercial shipping. “It would be different if they could have been finished right after the war started,” Iura argued, “but the plans have only just been completed. It will take at least two years to build the subs. Even their planes have just begun testing.… They cannot be relied upon to have a substantial impact.”15

  It was a radical departure from Yamamoto’s vision, and Iura was not alone. Several sub captains were also against the I-400s. They believed launching and retrieving sub-based aircraft in a combat zone was tantamount to “suicide.”16 Calls to scale back or cancel the program only increased.

  Perhaps the most compelling argument for killing the program was the Battle of Midway. After Midway Japan increasingly fought a defensive war, and as the Japanese Empire focused on protecting its perimeter, there was less need for large-scale submarines to attack the U.S. mainland. Had the subs been completed shortly after Pearl Harbor, everything might have been all right. But the subs were at least a year from being finished. Time was running out.

  Iura represented a formidable rear guard. But sometimes it’s more dangerous to kill a project than to leave it alone. When it was suggested to Ariki Katayama that they stop production, the man responsible for building I-boats cunningly replied: “It may not be possible.… Material for four I-400 subs has already been ordered and preparations are under way.”17

  It was a classically Japanese way of skirting the issue, no less effective for being indirect. After all, the I-400 squadron was Yamamoto’s idea, and though his recent spate of losses had humbled him, he was still commander in chief of the Combined Fleet. That is, until the United States miliary decided to kill him.

  Yamamoto was on the island of New Britain preparing to fly from Rabaul to Bougainville when the United States made its move. It was a few minutes before six A.M., April 18, 1943, just two weeks after Yamamoto’s fifty-ninth birthday. The morning was sunny and hot as his Mitsubishi twin-engine bomber lifted off the runway into the clear blue sky. Bougainville was only an hour and a half from Rabaul, yet Yamamoto’s plane and an accompanying “Betty” bomber were escorted by six Zero fighters in case of enemy attack.

  What Yamamoto didn’t know was that U.S. cryptographers had broken the Japanese naval code and knew in advance exactly where he was going. Eager for revenge, 18 P-38s were sent to shoot down the architect of the Pearl Harbor attack. Yamamoto flew straight into an ambush.

  The death of the Combined Fleet’s commander in chief had devastating consequences. Talent was thin at the top of the Imperial Japanese Navy; replacing him would not be easy.18 Importantly, everything Yamamoto had worked on was thrown into doubt, including the I-400 program. It wasn’t long before reactionary forces had their knives out. Now that Yamamoto was dead, they would have their day in the sun.

  * Though sources agree that Seiran floats could not be jettisoned, there appears to have been a discussion during the design stage about adding this feature.

  PART III

  COMPLICATIONS

  CHAPTER 8

  REDUCTION AND REVIVAL

  THE COMBINED FLEET WAS SEVERELY SHAKEN BY THE DEATH OF its commander in chief. Yamamoto may have had mixed success, but nobody expected him to be carried off the battlefield. The Japanese public wasn’t informed of his death until more than a month after it happened. When it finally was announced, Yamamoto was awarded the Order of the Chrysanthemum First Class and posthumously promoted to fleet admiral. Still, it was just papering over the loss.

  Rear Admiral Yamaguchi was supposed to succeed Yamamoto. But when he lashed himself to his sinking carrier at Midway, the IJN lost a competent replacement.1 Adm. Mineichi Koga, Yamamoto’s actual successor, was capable of bold thinking, but switching quarterbacks in midgame is tricky, especially when supporting players have trouble handling change.

  Interestingly, the IJN didn’t make a connection between Yamamoto’s plane being shot down and the U.S. ability to read their naval codes. In fact, the Naval High Command believed it was impossible. Their stubborn refusal to believe that their codes had been compromised blinded them to what many sub captains already suspected. It would prove a crucial error.

  Yamamoto had been dead less than a month when the jackals inside the NGS made their move. One of the I-400’s most powerful opponents was Shigeyoshi Miwa, chief of the Seventh Division, which had recently been created to o
versee all aspects of IJN submarines.2 Miwa had never liked the I-400s and was well positioned to kill the program.3 There were other factors working against the I-400s as well. The Allied advance had so tightened the noose that by mid-1943 steel shipments were in sharp decline. It was senior NGS naysayers who most hurt the program though. They were against the underwater aircraft carriers on principle, and with Yamamoto gone, they cut back the number of subs from 18 to 10.4

  Kurojima, Yamamoto’s confidant, was determined not to give up the fight. After the death of his mentor, he had been moved to the NGS as Second Division chief. This meant the “weirdo officer” was ideally placed to defend Yamamoto’s wishes. Like any good bureaucrat, Kurojima wanted to test the waters before deciding what to do, so he sent his staff officer, Lt. Cdr. Yasuo Fujimori, to investigate.

  Fujimori was a good choice to gather intelligence since his job allowed him to move freely among the various NGS factions. Taking his role to heart, Fujimori set about convincing Miwa to support the program. But Fujimori faced an uphill battle. Twice he tried persuading Miwa, and both times he failed to change the stubborn officer’s mind. The second time Miwa got so angry, he told Fujimori never to bring the subject up again.5

  It’s unlikely that Kurojima was surprised by Fujimori’s failure. Miwa had never kept his feelings secret, and besides, Kurojima was only feeling him out before confronting the man himself. Fortunately, Kurojima had another card up his sleeve. When Fujimori reported his failure, Kurojima played his hand.

  “Immediately following the start of war, Yamamoto told us we must reach the U.S. mainland,” Kurojima explained. “This is why he ordered large-scale submarines that carry attack planes. [Given the war has changed,] we should now investigate how these can best be used to immediately revive their construction.”6