One of the most interesting, unanswered questions having to do with Japanese submarine operations in World War II concerns the sinking of the cruiser, USS Indianapolis, by I-58. How did it happen that the submarine found herself in such an advantageous position on 29 July 1945?
In his Abandon Ship, Richard F. Newcomb briefly touched on this point. He wrote that the submarine commander “seems to have known of the impending fate of the cruiser.” Actually, the meeting of the two vessels was coincidental. It can be said, however, that I-58 was on station at the point where a line joining Okinawa and Palau crosses a line from Guam to Leyte in accordance with a specific operation order. As a staff officer of the Sixth Fleet, which was the sole submarine fleet of the Japanese Navy at that time, I was responsible for drafting that order.
The dispatch of I-58 to a point where no submarines had ever been sent before was not planned overnight. To explain why and how she was ordered there needs, I think, some discussion of the development of the Japanese Navy’s submarine operations up to that time. Perhaps that can best be done in terms of my own experience.
Experience as Submarine Captain
Before I joined the staff of the Sixth Fleet in March 1944, I had been commanding officer of two submarines, Ro-64, an obsolete 996-ton craft, and I-165, a more modern vessel displacing 1,705 tons.
My first contact with the enemy was made on 25 August 1942 about 300 miles southwest of Colombo, Ceylon, where I sank a British merchantman with two torpedo hits. After the war, I learned she was Hermonides.
My withdrawal from the scene of battle, however, was not so successful as my attack. When I surfaced the ship after dark, we were suddenly lighted up by flares dropped from a plane. I dove. Terrifying indeed was the ensuing struggle between the hunters and the hunted. Only a few hours were left before dawn, when I managed to shake off the two or three enemy destroyers.
This experience in my first encounter with an enemy brought home to me the fact that because of radar, the cloak of darkness was no longer sufficient protection to the submarine. It also began to make me doubt the wisdom of employing underwater craft solely in a battlefront area.
From the outbreak of war, the Japanese Navy had stuck to its long-cherished “one- big-battle idea,” in which all naval arms, surface, air, and underwater, were to be used once and for all. The employment of the underwater arm was not excepted, even after the loss of Guadalcanal turned the tide against us.
As the defense perimeter had to be pulled back toward the homeland, all the forces of the Empire were fanatically thrown into the fight regardless of losses. Many submarines were ordered to attack Allied landing forces or to transport a small amount of badly needed supplies to hard-pressed, isolated islands. Fifteen submarines were lost by the summer of 1943.
Submarine crews were opposed to such deployment. They strongly advocated using their ships to intercept enemy communications lines instead, but they were overruled or ignored by the high command, which deemed it imperative to give “the last-minute shot” to half-starved troops trapped on tropical islands for the sake of getting co-operation from the Army.
This blunder in submarine employment was hard to remedy. As the mistake was repeated again and again, the loss of Japanese submarines increased. Six of them were lost following the Allied invasion of the Gilbert Islands. Of 38 submarines deployed to the Marianas area when those islands were invaded, 18 were lost. Eight submarines went missing; during the Philippine campaign in the fall of 1944.
Employment of Human Torpedoes
In the meantime, strenuous studies and efforts had been made in the homeland on how to save the ever-deteriorating submarine situation. Typical among them was a human- torpedo project, which was originally advocated by two young submarine officers, Lieutenant H. Kuroki and Sub-Lieutenant S. Nishina.
Kuroki and Nishina, both graduates of the Naval Academy, hated to see the deterioration of the submarine fleet, and they decided to do what they could by volunteering to man a large torpedo themselves and ram an enemy ship.
A concept that the Empire could only be saved by sacrificing blood had gradually been appearing elsewhere in the armed forces.
Early in the summer of 1944, both officers came to see me, for by that time I was an operations officer on the Sixth Fleet staff. The more they advocated their cherished plan for the use of manned torpedoes, the more I was impressed by them. Just a short time before, we had experienced our heavy losses in the Marianas. That action had convinced me that our submarines were no match for Allied warships, which were well equipped with sonar and radar.
I thought this weapon proposed by Kuroki and Nishina could and should be used in raiding enemy communications lines. It seemed likely to me that a manned torpedo could be released from a submarine and carry out its attack far enough away from the submarine to allow the releasing vessel to remain undetected—in contrast to my own experience off Ceylon. But I believed at the same time that this new weapon should not be employed until a sufficient number became available for operation.
My voice, however, was not yet strong enough to persuade other staff members to share my idea of employing manned torpedoes in raiding operations at sea. As soon as a dozen of the weapons were readied, it was decided to launch the first torpedo attack on Ulithi atoll.
The submarines I-36 and I-47, each carrying four manned torpedoes on deck, approached the entrance to Ulithi in the early hours of 20 November 1944 and launched one and four manned torpedoes respectively. These weapons were designated kaiten, meaning “make a big change like turning Heaven.” Some of them successfully penetrated the Ulithi lagoon through the gate, which had not been closed after the exit of three cruisers and four destroyers bound for Saipan, and hit a target, the fleet oiler Mississinewa. All of the kaiten crews, of course, perished, while both submarines returned safely to their home port, Kure in the Inland Sea.
On the other hand, the submarine I-37, which headed for nearby Kossol Passage met with bad luck. On 19 November, the day before the designated date of attack, this submarine was discovered at the west entrance of the passage and was sunk with her four kaiten by two escort destroyers.
As to the damage inflicted upon the enemy by this first human-torpedo attack, the Japanese Navy repeated an often-committed error in over-estimating that five carriers and battleships were sunk.
Further Efforts to Change Submarine Tactics
I hoped that this first human-torpedo attack would put an end to our usual tactic of employing submarines against a well-guarded enemy area. To try to bring this about, I took advantage of a naval general staff conference held by the Combined Fleet and the Sixth Fleet in early December on board Chikushi Maru, the flagship of the Sixth Fleet, by bringing up for discussion the submarine operations to be undertaken in the future.
I proposed that the news of the first kaiten attack be released on 1 January 1945. My reasoning was: (1) the enemy was believed to know about our human torpedoes, (2) similar subsequent attacks had less prospect of success against an enemy now on the alert for them, and (3) the loyal deed of those who had perished should be made known to their kin as soon as permissible.
My real purpose with this proposal was to discourage further attacks of this nature by making public the details of the first one. But, to my great regret, no one dared support my view. To my conservative colleagues, it was out of the question to employ kaiten in raiding operations at sea. The press release was, of course, postponed.
My disappointment was increased by my position, because as a staff officer for submarine operations, I had to help launch the second kaiten attack on American bases then presumed to be ready to defend themselves against an attack of this nature. This time, six submarines and 24 kaiten were gathered to attack Ulithi, Kossol Passage, Seeadler Harbor in the Admiralty Islands, Guam, and Hollandia. On 12 January 1945, all six submarines released their manned torpedoes as planned, but apparently little damage was inflicted upon the enemy. One of the six submarines failed to return.
In the meantime, I had informally contacted Lieutenant Commander Mitsuma Itakura, who was the commanding officer of the kaiten training center at Ootsujuma. Itakura was a veteran submarine officer with a great deal of battle experience, and he shared my views on how to employ submarines.
Complying with my informal request to train kaiten to attack a moving target, Itakura had vigorously pushed ahead such training, while informing me constantly of its development. As training progressed, it became possible to attack slow convoys with a good chance of success.
On the other hand, time was running out very quickly on the hard-pressed inner perimeter of the Empire. When Iwo Jima was invaded by the Americans on 19 February 1945, the submarines I-368, I-370, and I-40 were hurriedly ordered to launch a determined kaiten attack there. This attempt spelled another failure, however, for two of the three submarines were lost, and no enemy ships were sunk.
Iwo Jima was not the last graveyard of Japanese submarines. Greater losses came about one month later, when the mighty forces of the Allies seized Okinawa. With the grimmest determination, the Japanese Navy did not hesitate in sending against the landing force almost all the air, surface, and underwater forces it had. The desperate attempt to save the island was in vain.
Four submarines, carrying 20 kaiten, and five conventional submarines were ordered to attack the invading enemy. All but two of the nine failed to make port again. The only survivors were I-58, which never got through the enemy alert zone around the besieged island, and I-47, which had been damaged by air attack soon after her sortie from the homeland. I-58 was destined to attack Indianapolis about four months later.
The heavy losses in the Okinawa campaign left the fast-shrinking Japanese Navy only four large attack submarines and six transport submarines. There were also several obsolete boats, available for training purposes only. In addition, four 3,500-ton submarines, a dozen 1,000-ton, high-speed boats, and several 320-ton coastal submarines were nearing completion.
Direct Appeal to the Commander-in-Chief
There was no reason to doubt that all of the remaining submarines in operating condition would be expended in the desperate campaign around Okinawa. I believed that the time was long overdue to make a big change in the nature of submarine operations, as the name kaiten indicated.
I made a final attempt to persuade my superiors to accept my theory that the kaiten should be used to intercept Allied sea communications lines. My plea was at first bluntly rejected by the Chief of Staff, who further informed me that the Commander- in-Chief was of the same view. I then asked the Chief of Staff to relieve me from my post as a staff officer for operations, if my view on operations was to be entirely ignored. At this request, the Chief of Staff suggested I see the Commander-in-Chief, Sixth Fleet, Vice Admiral S. Miwa, and personally express my view to him.
My recommendation to Admiral Miwa was made in an operations room of the headquarters, with the Chief of Staff and other staff members also attending. I described in detail how futile the Okinawa campaign had been, and tried to show the uselessness of sending more of our submarines into the well- guarded sea around Okinawa. I stressed that the only means of employing submarines usefully under the extremely adverse circumstances with which we were faced was in raiding operations with kaiten against enemy convoys. In a recent experiment, kaiten had proved practical for such operations, I explained.
Finally, I added that my view on this new employment of submarines was shared by almost all the submarine skippers and crews, and also that all preparations necessary for conducting raiding operations at sea had already been completed.
By that time, the Empire was hard pressed on all sides. Its outer perimeter in the Solomons, Gilberts, Marshalls, Marianas, New Guinea, and the Philippines, had long since collapsed, while its inner stronghold had just been punctured at Iwo Jima and Okinawa. Clearly, desperate measures were called for.
Admiral Miwa listened very attentively to my suggestions on the new employment of the remnant of his submarine force. Seemingly, he had some difficulty in making a decision, but he finally approved the use of two submarines scheduled for the next operation, I-36 and I-47, in a raiding operation at sea.
This decision was reported immediately to higher command in Tokyo. The Combined Fleet command gave ready approval to the submarine fleet’s decision, but the Naval General Staff was harder to crack. It was only after a long, argumentative telephone conversation that its staff in charge of operations finally gave in, on the condition that this operation would not be repeated.
Kaiten Attacks on Ships at Sea
The submarine I-47 left Kure on 20 April 1945, and I-36 sortied two days later. Each carried six kaiten on deck, assigned to the new mission of attacking enemy ships at sea.
I-47’s patrol station was between Ulithi and Okinawa, and I-36 was to operate between Saipan and Okinawa. Until then, Japanese submarines had never been used to interrupt the enemy’s line of communication between a newly invaded point and his rear bases.
While submerged at dawn of 27 April, I-36 discovered on the brightening horizon far to the south a group of ships which soon turned out to be over 30 vessels apparently heading for Okinawa.
Immediately, orders for preparing a kaiten attack were given. Out of six human torpedoes, two were found to be of no use.
When the submarine had closed to a point some 7,000 meters forward of the beam of the enemy convoy, four kaiten were released. There was no indication that I-36 had been detected. Ten minutes after launch time, four big explosions were heard. The submarine was not subjected to counterattack by the enemy, but she failed to confirm the result of her kaiten attack. How much damage this first kaiten attack on ships at sea inflicted is still unknown to us.
In the meantime, I-47 had been patrolling between Okinawa and Ulithi. After dark on 1 May, her newly-installed radar picked up a target, and the submarine closed the range in a rough sea. At 10,000 meters, I-47 dove without having gained visual contact.
About 25 minutes after submerging, the ship was in a favorable position, some 4,000 meters forward of the beam of the target, and she fired four ordinary torpedoes. Through the periscope, the skipper confirmed three hits.
The unexpected good luck of I-47 had not ended. At 0930 on the following morning, a sonar contact was gained, which soon turned out to be two transports and two escort ships. Two kaiten were ordered to attack them, and two big explosions shook the submarine 21 minutes and 25 minutes respectively after they were released. Taking advantage of this success, I-47 released one more kaiten soon afterward to attack the two escort ships. This time, an explosion was heard 48 minutes later. The skipper of I-47 believed most of the attacks she delivered were successful, although they were unconfirmed.
I-47 shifted station to a point between Okinawa and Guam soon after this successful attack. At 1100 on 6 May, the submarine picked up what seemed to be a cruiser. Twenty-four minutes after a kaiten was released, a big explosion convinced the crew that the enemy cruiser had been sunk by the kaiten.
Sortie of the Submarine I-53
How much damage these kaiten attacks inflicted on the enemy was, and is, still unknown to us, but their reported results, though unconfirmed, sufficed to convince our commanders and staff that this new tactic of employing submarines in raiding operations was far more effective than the previous tactic of sending them into well-guarded areas around bases.
A striking contrast to the sea raiding operations was the fact that out of 12 submarines which had been deployed in the vicinity of Iwo Jima and Okinawa, eight failed to make port again. No longer were there any grounds to stick to the past policy, which had proved a failure.
The operational policy of the Sixth Fleet was then switched entirely to raiding operations at sea. As the second attempt, I-367 made a sortie on 5 May to patrol on the line connecting Okinawa and Saipan, where she destroyed USS Griggan, a destroyer, with two kaiten.
In the final attempt, this time with six submarines, I-47, I-53, I-58, I-363, I-366, and I-367, I-53 was assigned an area between Okinawa and Leyte, and I-58 went to a station between Leyte and Guam.
I-53 was first to bag game. On 21 July, she destroyed the transport Marathon, and three days later, she sank the destroyer escort Underhill.
I-58 made her first contact on 28 July when she discovered a large tanker. The oiler was believed to have been sunk by two kaiten.
After this attack, I-58 proceeded to the point where the Okinawa-Palau line crosses the Guam-Leyte line, the point where she met USS Indianapolis on 20 July.
The contacting and sinking of that vessel, from our viewpoint, was a fortune of war that showed our newly adopted submarine tactics to be correct. To the Americans, the loss of this vessel with so many of her officers and men, so near the end of the war, was undoubtedly a most painful misfortune.
Editor's Note: Of the results claimed for Japanese submarines in the above article, only I-58’s sinking of Indianapolis can be strictly upheld. I-53 did, in effect, sink USS Underhill (DE-682), for that ship's bow was blown off, and her stern section had to be sunk by gunfire from accompanying vessels once survivors were clear. It is also true that I-53 damaged USS Marathon (APA-200), but she did not sink her. There has never been a ship named USS Griggan. There is no report of further damage by the submarines mentioned.
A graduate of the Japanese Naval Academy, Mr. Torisu is a former commander and submarine officer in the Imperial Japanese Navy. From March 1944 until the end of World War II, he served as an operational staff officer of the Sixth Fleet, the Japanese submarine force.
Also a graduate of the Japanese Naval Academy, and a former commander in the Imperial Japanese Navy, Mr. Chihaya is now the managing editor of Shipping & Trade News and Japan Shipping & Shipbuilding, both English language magazines published in Japan.