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

by John Geoghegan

  As for the Segundo herself, she returned to Pearl Harbor after Japan’s surrender. Two of her crew managed to get arrested for taking a post office motorcycle for a joyride during their stay.12 The sub sailed for Seattle shortly afterward and then took a victory cruise down the west coast.

  The Segundo received four battle stars for her World War II service and was eventually assigned to SubRon 3 in San Diego. She was modernized in 1951 in the San Francisco Naval Shipyard, where she was equipped with a snorkel—which Ariizumi would have appreciated. She served numerous tours in the Far East and saw action during the Korean War. Finally, after 26 years of duty, the Segundo was found “unfit for naval service” and sunk during target practice on August 8, 1970.13

  SEN-TOKU OFFICERS AND CREW

  Having spent 1,380 days fighting in the Pacific,14 the I-401’s captain, Lt. Cdr. Nobukiyo Nambu, struggled to make a living after the war. Trained to serve a navy that no longer existed, Nambu’s life became so grim he couldn’t feed his growing family. At one point, he even took in boarders to make ends meet, yet still insisted on bringing former naval officers home for dinner, much to his wife’s annoyance.15

  Nambu continued to be questioned by occupation authorities about his former squadron commander but was never charged with any crime.16 When the predecessor to today’s Japanese Maritime Self Defense Force (JMSDF) was reconstituted in 1952, Nambu joined up. He moved from Kure to Maizuru, close to where the I-401 had undergone her final training, and eventually became superintendent of the JMSDF Submarine School; he retired as a rear admiral in 1965.17 Like Yamamoto, Nambu enjoyed writing poetry and in 1963 was awarded a prize for his efforts by Emperor Hirohito.18 As of this writing, he lives in an assisted living facility outside Tokyo. Even at age 97, the captain of the Sen-toku subs’ flagship remains unstooped with a sharp mind and crisp salute, though his hearing isn’t what it used to be.

  Had Cdr. Tatsunosuke Ariizumi lived to see a final accounting of his Sen-toku squad, he would have been depressed. All five subs (I-13, I-14, I-400, I-401, I-402) lay at the bottom of the Pacific. Construction on the I-403 had been canceled in October 1944,19 while the I-404 was almost complete when Allied bombs destroyed her while moored near Kure in July 1945.20 The I-405’s keel was laid down in September 1944, but work stopped in January 1945,21 and the sub was dismantled. Hull numbers 406 through 417 were never built, since shifting priorities led to the remaining I-400 subs being canceled altogether.

  The I-402 was the only other I-400 sub to become operational during the Storm mission. Commissioned on July 24, 1945,22 just a few days after her sister subs departed for Ulithi, she was captained by Cdr. Otoji Nakamura, and immediately commenced training as part of SubRon 1. She was slightly damaged on August 11,23 when shrapnel from a Kure bombing raid punctured one of her fuel tanks. When the cease-fire was declared, she was still undergoing her shakedown period.

  As for the remaining Type A modified subs, sisters to the I-13 and I-14, the I-1 was 70 percent complete when she sank in a storm off Kobe in September 1945;24 the I-15 was also unfinished when the war ended and was scrapped. Three additional AM-type subs never got past the planning stage.25

  The Allied investigation into war crimes soon uncovered Ariizumi’s role in the Indian Ocean massacres. For a while, Allied authorities sought to determine whether Ariizumi might still be alive. Over time, however, they accepted that he’d killed himself just as Nambu described.

  Suprisingly, some of the Segundo’s crew believe Ariizumi’s body was cremated in a rice kettle aboard the I-401. Later there was speculation that Nambu killed Ariizumi after the commander threatened to scuttle the sub,26 but the story is preposterous. Ariizumi is on record as having specifically asked the 631st chief medical officer,27 as well as Yata, the chief gunnery officer,28 about the best way to kill oneself with a pistol. Additionally, Ariizumi was clearly in psychological distress, not because of his role in the I-8 massacres but because surrender was unimaginable. Given that Ariizumi probably felt as betrayed by his naval command as shaken by defeat, it’s not surprising he killed himself. Everything he believed in had been destroyed.

  Certainly, there was no love lost between Ariizumi and Nambu. Still, it’s highly unlikely that Nambu would have turned a gun against his commanding officer given his belief in naval protocol. Even now, 66 years after the I-401’s surrender, Nambu refuses to speak critically of his commanding officer.

  Matsu raised Ariizumi’s five children in the manner he would have wished, and though the family keeps a low profile, refusing to speak to the media (including the author), relatives have occasionally appeared at I-401 reunions.29

  Muneo Bando, the I-401’s chief navigator, eventually got involved in real estate and is a rightist in his political views. He is a member of one of Tokyo’s most prestigious clubs, from which the emperor’s palace can be seen, and remains a somewhat controversial figure at I-401 reunions, since his recollections don’t always square with those of his former shipmates. Nevertheless, it’s not hard to see what Captain Johnson found so endearing about the little navigator.

  When the IJN was reconstituted as the Japanese Maritime Self Defense Force, Nambu wasn’t the only Sen-toku officer to return to his former career. Tsugio Yata, the I-401’s chief gunnery officer, also signed up. In fact, Yata eventually rose to the rank of admiral, surpassing Nambu, whom he’d always admired. He served as the thirteenth chairman of the Joint Staff Council at Japan’s Defense Agency, a position similar to the chairman of the Joint Chiefs of Staff in the United States. In a 1981 ceremony attended by Mrs. Douglas MacArthur, the United States awarded Yata the Legion of Merit (Degree of Commander) for exceptionally meritorious conduct in the performance of outstanding services. It was the same award Captain Johnson received for capturing the I-401. Yata retired from the navy in 1983 and lives with his wife in a suburb outside Tokyo.

  Yata’s mother also survived the war. Though she’d intended to kill herself after her son left on Operation Storm, she delayed doing so, hoping he’d return. Had she received the farewell note Yata had planned to send her, she confessed, she would have hung herself. It was Nambu’s kind invitation to say goodbye to her son that saved Yata’s mother from death.30

  The Sen-toku squad’s mission was so secret that Inouye, the I-401’s sonar operator, could not tell his parents where he was going, what he was doing, or whether he’d return. When months passed and Inouye’s parents heard nothing from him, they assumed the worst. But when he returned home as a “ghost” in the fall of 1945, they were overjoyed. His two older brothers also survived the war, which was uncharacteristically lucky for a Japanese family. Inouye later went to work for Toyota Motors. For the past 35 years, he’s run a small ramen shop with his wife in Nagoya, not far from where the Seiran were built.31

  After the war, the I-400’s commanding officer, Cdr. Toshio Kusaka, skippered a surface ship to return demobilized soldiers to Japan.32 He was later tried and found guilty by the Yokohama War Crimes Tribunal for massacring the survivors of the SS Richard Hovey. He was sentenced to five years’ hard labor in Sugamo Prison and was released after serving his sentence.33 He later captained merchant marine ships and died in 1999 at the age of 95.34

  On the other hand, Cdr. Tsuruzo Shimizu, captain of the I-14, lived up to his lucky reputation. After starting over as a farmer, he was arrested in October 1948 and confined to Sugamo Prison for atrocities committed while captaining the I-165. He was acquitted, however, on December 13, 1948. Though the reasons for his acquittal are unclear, it certainly wasn’t because he was innocent. Most likely, evidence was lacking or a deal was struck in exchange for his cooperation. He too entered the JMSDF, eventually serving as vice-superintendent of the Yokosuka Naval Base, and retired as a rear admiral in 1963. He died in December 2001.35

  THE PILOTS

  Ens. Kazuo Takahashi, the I-400’s Seiran pilot, managed to avoid being tried as a war criminal despite his participation in the I-37 massacres. After living a long, productive life, he d
ied in March 2005.

  Lt. Atsushi Asamura, the Seiran squadron leader for the I-401, lives in Tokyo with his wife. His apartment boasts a scale model of a Seiran and a photo of himself as squadron leader. He keeps in touch with his colleagues and is an unofficial spokesman for the Sen-toku subs, often granting television and magazine interviews. Even today he remains a stickler for protocol and has few kind words to say about his fellow Seiran pilot Takahashi. Not surprisingly, Asamura comes across as an unreconstructed war veteran, ready to jump into his Seiran and finish the job he started.

  Reunions for the respective Sen-toku subs continued for many years after the war, though the number of attendees declined as death took its toll. Many of the I-401 crew remain grateful to Nambu for returning them to Japan. But the I-401’s failure to communicate the change in rendezvous date and location to the I-400, as well as the conflict between Ariizumi and Nambu, splits the crew to this day.36 When pressed for details, all Tsugio Yata will say is: “The captain is head of the sub, whereas the squadron commander is not. I suspect the opinions of Commander Ariizumi and Lt. Commander Nambu did not reach agreement.”37

  Nambu remains equally reticent. Despite having been on the receiving end of Ariizumi’s psychological troubles,38 he continues to praise his commanding officer despite their differences, saying: “I have avoided all speculation and believe the Commander was a brilliant naval officer who committed suicide in the bushido tradition. I have written as much and my belief will remain this way.”39

  Many I-401 officers praise Ariizumi for his strength of character in accepting responsibility for their mission’s failure. “He was a great soldier,” Muneo Bando, the I-401’s navigator, says. “He even took his own life for his crew and country.”40

  As for Nobuo Fujita, the pilot who firebombed west coast forests from his sub-launched seaplane, he returned to Oregon in 1962 to make amends. Fujita was deeply ashamed of his attack on the U.S. mainland and traveled to Brookings, Oregon, to present his family’s 400-year-old samurai sword as a symbol of his regret. Fearing the Brookings townspeople might still be angry, Fujita was prepared to disembowel himself should things turn ugly. Fortunately, it never came to that. Later he donated $1,000 to the local library to purchase children’s books about Japan so there wouldn’t be another war between the two countries. He died of lung cancer in 1997 at age 85.41

  Perhaps the most unusual farewell for anyone associated with the I-400 subs was the funeral of Hiram Cassedy. Cassedy had briefly commanded the I-400 and later sailed the I-14 to Pearl Harbor. In keeping with his flamboyant personality, Cassedy’s ashes were placed in the forward torpedo tube of an experimental submarine and fired into the deep blue sea.42 Presumably, he went without any Japanese naval swords.

  Of course, the Tokyo War Crimes Tribunal took its toll on the IJN High Command. The Sen-toku crews were interrogated about Ariizumi and the I-8 atrocities.43 Even Carlo Carlucci was interviewed by U.S. naval intelligence when he returned to New York in 1946. “I was shown pictures of various Japanese naval officers and asked if I could identify any of them,” Carlucci remembers. “They all looked alike, but I picked out one that I’d seen on the bridge staring at us with anger in his eyes.”44

  After the war, there was a trial involving participants in the Indian Ocean massacres. Vice Adm. Hisashi Ichioka, who commanded SubRon 8 when the atrocities occurred, received 20 years. Other punishments were harsher. Admiral Daigo, the sixth CINC of the Japanese sub force in five years, was executed by firing squad in 1947. Declining a blindfold, the commander in chief of the Sixth Fleet sang the “Kimigayo,” Japan’s national anthem, before declaring banzai three times in honor of the emperor. When he finished, he calmly told the firing squad he was ready. Some of Daigo’s officers claimed he had nothing to do with the atrocities. Six years after the Ichioka defendants were convicted for massacres committed in the Indian Ocean, their sentences were commuted.45

  Chief of the Imperial Japanese Army General Staff Yoshijiro Umezu, who had canceled Operation PX—the plan to attack America with biological weapons—was arrested by SCAP authorities and tried as a war criminal. The International Military Tribunal for the Far East in Tokyo found him guilty of waging a war of aggression and sentenced him to life imprisonment. He converted to Christianity while in prison and died from rectal cancer in 1949.

  As for the brain trust behind the Sen-toku subs, NGS submarine staff officer Cdr. Shojiro Iura was found guilty of failing to restrain his subordinates from killing more than 800 prisoners in the Indian Ocean and was sentenced to six years of hard labor at Sugamo Prison.46 He was eventually released and wrote a book about his experience. Cdr. Yasuo Fujimori, who headed up the submarine section of NGS’s First Division, was found guilty of similar crimes and sentenced to four years’ hard labor.47

  Kameto Kurojima, Yamamoto’s favorite naval officer, was a rear admiral by the time the war ended. After Yamamoto’s death, he became director of the NGS’s Second Division, where he developed suicide attack plans, believing it impossible to win using conventional tactics.48 After the war, the “weirdo officer” cooperated with SCAP authorities. As Yamamoto’s chief of planning, he provided invaluable information about the attack on Pearl Harbor and the Battle of Midway. He was not charged with any war crimes and died in 1965.

  AFTERMATH

  Aichi, the Serian manufacturer, was dissolved after the war. In its current incarnation (Aichi Machine Industry Co., Ltd.), it manufactures light trucks and automotive parts for Nissan. The private shipyards that built the Sen-toku subs continue to exist, including Kawasaki Heavy Industries.

  At least one Seiran was brought to the United States after the war. Transported by a U.S. aircraft carrier along with a number of other Japanese aircraft, the last Seiran ever built (airframe no. 28) was studied to see if it might be of future use. When it was determined that the United States had no need for such a specialized attack plane, the Seiran was housed at the Alameda Naval Air Station. Ravaged by souvenir hunters and inclement weather, she was finally shipped in an advanced state of disrepair to the National Air and Space Museum in 1962, where she remained outside for another 12 years until room was found inside a storage facility.49 Over the next ten years, she was lovingly restored at a cost of $1 million and is now on display at the Smithsonian Air and Space Museum’s Udvar-Hazy Center, near Dulles International Airport in Virginia. Asamura was reunited with his beloved Seiran in 2003, when the Smithsonian invited him to experience it firsthand. Though beautifully refurbished, she is not capable of flight—something the residents of Washington, D.C., must feel relieved about.

  A Nanzan was also reportedly brought to the United States. Last seen in poor condition at Seattle Naval Air Station during the 1950s, she disappeared without a trace and is presumed to have been scrapped.50

  Despite finding Nambu’s sub, the I-401, and Shimizu’s I-14, the Hawaii Undersea Research Laboratory (HURL) has yet to find the I-400. The general location of Kusaka’s sub is known, and it’s probably just a matter of time before HURL locates it during one of its test dives.

  REAPPRAISAL

  Many naval historians view the Sen-toku squad as a dead branch on the family tree of submarines. But the story of Yamamoto’s underwater aircraft carriers is by no means over. What was once dismissed as an “undersea dinosaur”51 takes on a more meaningful role when one realizes the I-400s were the strategic predecessors to today’s ballistic missile submarines.

  For example, Rear Adm. John D. Butler gives partial credit to the I-400s for the Regulus missile program,52 lending credence to various paternity claims. Certainly the resemblance between the I-400 subs and the Regulus missile–carrying subs is striking.

  The Regulus missile program began eight years after the war ended. A primitive version of the Tomahawk cruise missile used today, Regulus missiles carried a thermonuclear warhead and were stored inside a sub’s massive watertight deck hangar, similar to the I-400s. They also required a sizable platform for launching—another link to I-
400 paternity.

  The first Regulus missile was launched from the deck of the USS Tunny (SSG 282) in July 1953. The Tunny and her sister sub, the USS Barbero (SSG 317), were retrofitted with a giant watertight hangar to carry the missile. They were later joined by two purpose-built Regulus submarines, the USS Grayback (SSG 574) and USS Growler (SSG 577) in 1958, and the nuclear-powered USS Halibut (SSGN 587) in 1960. Together these five boats formed the first U.S. nuclear deterrent patrol submarines.53

  The ability of U.S. submarines to launch nuclear weapons undetected became the backbone of the nation’s strategic deterrent force. At the very least, then, the Regulus missile program marked an important evolution of the I-400s as an offensive weapon. The I-400s helped demonstrate that a large, stable sub with a watertight deck hangar could be built to launch an offensive airborne weapon against an enemy’s cities.54 The Regulus subs even suffered the same tactical disadvantage as the I-400s—they had to surface before launching, making them vulnerable to attack.

  The successful development of the underwater-launched Polaris missile put an end to the Regulus program. Nevertheless, Regulus missile subs were clearly a strategic descendant of the I-400s. Other accounts suggest I-400 sub design was incorporated into the U.S. Navy’s next generation of Tang class submarines, just as Wernher von Braun’s V-2 program became the backbone for later U.S. ballistic missile and space programs. This probably gives the technology more credit than it warrants. Still, the I-400s proved it was possible to build a stealthy and stable underwater launch platform when it came to developing nuclear missile submarines.

  LEGACY