Manned by a mixed crew of U.S. naval officers and Japanese sailors, the mammoth Sen-Toku I-401 cruises near the Yokosuka naval shipyard, hours after her name is permanently struck off the roster of the Teikoku Kaigun on the 15th of September in 1945.
Hereafter she was no longer a submarine of the imperial Japanese navy but for a short while had remained with the U.S. navy to be studied in detail and eventually scuttled near Hawaii to keep her out of the hands of the American’s one-time ally, the Soviet Union.
The scene on that day had played out smoothly. No objections were raised. No questions were asked. The once-mighty Teikoku Kaigun now bereft of authority had virtually no power left to decide the fate of what once was the pride of their submarine fleet.
Not since their supreme commander, the emperor Michinomiya Hirohito, had announced the unconditional surrender of Japan and brought the juggernaut conflict that was World War II to an abrupt end – almost a month before the handing over of the submarine.
With the gradual passage of time Hirohito’s Japan had turned into a U.S. Protectorate. U.S military bases had sprung up over former Japanese strongholds. Diplomatic ties had been reestablished and the dissension that Hirohito’s rescript had initially sowed among the ranks of the Japanese armed forces had eventually petered out – as his countrymen had come to terms with events and rise above the very martial honour that had once made them ready to embrace death over surrender.
As this tide of change had swept even further, Harry S. Truman’s decision to drop the atom bombs had come to be criticized and by 1947 the cold war between the U.S. and Soviet Union had begun to rage.
Yet all this while, even as change was sweeping across the surface, and right up till the introduction of the nuclear powered ballistic submarine, the Sen-Toku I-401, inspite of resting at the bottom of the sea, remained the undisputed monster of the deep.
The Tokugata class of Submarines.
A technological marvel of the mid 19th century, and officially the largest submarine to have served in World War II, the Sen-Toku I-401 was the pride and flagship of the Tokugata class of Submarines – which by the virtue of their technology and size, were the most advanced to have sailed the oceans during the time of the intercontinental war.
Spotted and boarded by the USS Segundo, a Balao class submarine, returning home from her patrol at Honshu on the 28th of August 1945, these Japanese submarines were produced over a span of three years on the orders of the Commander-in-Chief of the Japanese Imperial Fleet, Admiral Isoroku Yamamoto. More famously known across the world as the mastermind behind Japan’s victory at Pearl Harbour.
This class of submarines were specifically conceived to bomb U.S. coastal cities and other targets, undetected by U.S. warships and radar.
They were designed for stealth and psychological warfare and their objective was not to deter or defeat but delay U.S. forces from launching a full-scale offensive – in order to gain imperial Japan precious time to extend her dominion over the Pacific, especially oil fields.
Underwater aircraft carriers.
What had made these monster submarines even more unique was that they were designed to launch attack planes like aircraft carriers, and which also makes the Tokugata class a testament to the engineering ingenuity of Japanese naval engineers.
Who had modified several features of submarine design and ultimately fused two submarine hulls together to make these monsters both operational and buoyant, albeit not without flaws. Despite being enormous in size and menacingly lethal, they were cumbersome to operate, easy to spot from the air and difficult to manoeuvre under the waves.
Out of a proposed ten, only five were sanctioned to be built, and out of these five, only three were actually built between 1943-45.
Each of these were some 390-400 feet in length and equipped with watertight hangers for housing three special attack planes, a deck ramp for the planes to take off, and a crane to lift the planes onto the submarine, once their task was accomplished.
Additionally each was also fitted out with eight torpedo tubes, anti-aircraft guns, lighter machine guns, and a 25 mm deck gun that was powerful enough to punch through thick enemy armour.
Furthermore, the hulls of this class of submarines were specially coated to reflect radar waves back into the ocean to make them practically invisible to long-range enemy scanners.
These submarines were also designed to circumvented the earth one and a half time without stopping to refuel, and remain on patrol for almost 120 days.
However, since these submarines were commissioned late in the war, they played absolutely no part in the Pacific conflict, and which leaves their combat capabilities to be determined by theory alone. Out of the three built for service, the I-401 and its sister ship the I-400 were the only two to have sailed on a combat mission.
The flagship Sen Toku I-401.
Constructed at the Naval shipyard of Sabeso and registered at the Kure Naval arsenal, the I-401 was launched on the 11th of March in 1945.
Among her proposed but never executed missions, was the intended destruction of the Panama Canal and the bombing of the city of San Francisco, in retaliation for the incendiary bombing of Tokyo by the U.S. Airforce on the 9th of March in 1945.
Prior to Japan’s surrender on the 28th of August in 1945, both the I-401 and I-400 were tasked to attack a U.S. fleet of aircraft careers at the Ulithi atoll. They had been ordered to carry out the mission by deploying their three special attack planes known as the Serians.
The Ulithi Atoll was a strategic location in the Western Pacific Ocean. Her capture by U.S forces and the subsequent construction of a naval base had brought the war right to the doorstep of Japan. Thus, the Ulithi Atoll towards the end of the war was a threat for Japan, requiring counter-offensive measures.
Surrender of the I-401.
The I-401 had sailed for her final mission from the naval base of Ominato in Honshu on 23rd of July in 1945. En route to her destination she had come close to being blown apart by friendly fire in the Tsugaru Strait, which separates the islands of Honshu from Hokkaido.
Before reaching the Ulithi, however, she had received the radio broadcast of Emperor Hirohito’s surrender on the 15th of August in 1945. Yet, unsure and with no specific orders to abandon the mission she had continued on her journey.
On the 26th of August in 1945, direct orders from the Japanese Admiralty had made her hoist the black flag of surrender and jettison her planes, torpedoes, secret documents and other weapons for defence. Barring aside the deck gun.
By the time the USS Segundo had closed in on her, the Sen-Toku I-401 had little onboard to defend herself. Despite its superiority and greater chance of surviving a naval battle, the monster submarine had allowed five officers of the USS Segundo to board her. The Sen-Toku I-401 had evade the USS Segundo till her commanders, Nobukiyo Nambu and and Tatsunosuke Ariizumi, had decided to surrender and not have her scuttled.
After surrender, I-401 had been steered towards the naval base of Yokosuka with her hatches open and chained to prevent her from submerging. On the 31st of May 1946, some nine months after her capture, the submarine was used as ‘target practice’ by the U.S. Navy – with specific orders of having her scuttled. She was sunk with two Mark 18 torpedoes fired from the USS Cabezon another Balao class submarine.
The photo.
This photo was produced by a photographer whose name is lost to time. It may have been taken by a seaman or official from the dock or another sea vessel, possibly, a U.S. Navy personnel.
The Nihongo words Sensuikan Tokugata, Tokugata and Sen-Toku were interchangeably used to refer to this special class of submarines. Literally translated into English, they stand for Special Submarines or Submarine Special.
I F I This is an Independent story produced to highlight this featured Vintage photo of Japanese submarine Sen Toku I-401 from 1945. The story also sheds light on the design and nature of these monstrous Tokugata class of Submarines from World War II and what made them special. It has been created from facts curated out of literary and historical sources. I
