The turning point in the submarine war came when all enemy ships and aircraft were fitted with efficient radar sets. I have already quoted many examples of the way our own submarines were handicapped by having no radar. Here are some of my own experiences.
Submarine RO-44, of which I was captain, completed her fitting out and began trials in September, 1943. At the time fitting submarines with air radar had scarcely been considered. During our trials with surface radar I had spoken with Captain Ito of the Naval Technical Department, who told me that he had pressed for the immediate fitting of a set, then in existence, which had a range of about eight thousand yards. Knowing that the Ministry of Marine authorities was somewhat lackadaisical despite knowledge of front-line conditions, he had urged the Staff Officer of the 11th Submarine Squadron to go up to Tokyo to press the matter personally. Unfortunately this officer was transferred elsewhere just when he had obtained permission for the Tokyo visit, so nothing more came of the proposal. Matters just couldn’t be left as they were so I asked to be allowed to go myself, but this was not approved. At this point I went to see a radar set said to be in use at the Kure Naval Air Station. It was portable and easily capable of being fitted in a submarine. I came rushing back and persuaded the Staff Officer Submarines to ask the captain of the Naval Air Station to lend it to us. He gladly gave his approval, and late one Saturday afternoon we brought it over on a truck from the Kure dockyard electrical department. It was tested out and adjusted on the Sunday and placed on board by the time we left harbor for trials on the Monday.
That day, November 13, I got the Kure Naval Air Station to send out a target aircraft and RO-44 was excused from other exercises in order to carry our radar trials. We started off in the calm conditions of Ise Bay. The set proved to be very inaccurate. When the target aircraft developed engine trouble we had to abandon testing that day. The next day there were ideal flying conditions and we started out again early in the morning. This time reception was good for distances from five to six thousand to a maximum of fourteen thousand yards. True, these were not exceptional results, but even so, they were a great improvement on our previous helpless state. An urgent signal, supported by the senior officer of 11th Submarine Squadron, was sent to the proper authorities stating the results of the trials. This brought back a reply asking why trials had been carried out without the approval of the Naval Technical Department. All hope of action subsequently faded away.
I tried again to get permission to go to Tokyo with plans for radar to be fitted in RO-class submarines, but couldn’t get approval for the trip. Meanwhile, we were about to leave for Maizuru to make final preparations for active service. This meant that we left the 11th Submarine Squadron and joined the 6th (Submarine) Fleet. I persisted with my request to visit Tokyo and at last it was approved, and I had a chance of expressing my views at a Naval Technical Department meeting. The senior member present proceeded to bring up a number of objections and said that new equipment, designed by the Technical Department, would soon be ready and we’d better wait till then. As it happened the radar set designed by the Naval Technical Department had been under test at Kure dockyard. The senior technician there had told me there was no prospect of early action, and this was what prompted me to carry out trials in RO-44! Anyway I could get no satisfactory answer and the meeting decided to shelve the matter. This was most unsatisfactory, so, refusing to be put off, I went the next day to the Technical Research Bureau, where I was received much more enthusiastically. We went into all the technical difficulties and were able to reach workable solutions. Thus armed, I put in a second appearance at the Naval Technical Department and tried to carry my point, but the Research Bureau’s solution was not accepted. I think it was a case of interdepartmental jealousy. I had no time to argue any further for I had to return to Maizuru. All I had succeeded in getting was approval for the increased allotment of one pair of binoculars for lookout purposes! It was indeed regrettable that our Headquarters Staff were more concerned with preserving their dignity than giving proper appreciation to active service conditions.
Soon afterward, at the end of December, we left for the southern battle area, still without radar. Our course took us through the Bungo Channel and as this was a favorite spot for lurking enemy submarines, we made what speed we could by night and dived each day at dawn. The thought of having to cruise submerged when so close to Japanese waters was not a pleasant one, but such were the hard facts of war. The second night at sea brought us beyond the danger area and after that we cruised entirely on the surface. At that time all was well in the Marshalls and at Rabaul, and as far as Truk we could anticipate no worries from enemy aircraft. We passed New Year’s Day, 1944, at sea, and only ten days after leaving the blizzards of Maizuru, we were basking in tropical heat. We reached Truk in early January. It was a grand sight to see the Yamato and the greater part of the combined fleet at anchor. I reported forthwith to the C.-in-C. 6th Fleet and described my efforts to get air radar to the Senior Staff Officer. I-185 had left Japan on operations at the same time as we and had gone to Rabaul where her captain had made a similar report to the C.-in-C. SE. Area Fleet. Fortunately there was a spare aircraft radar set available and I-185 promptly had it fitted. The results it gave were better than those obtained when I tried out the same equipment in RO-44. This was duly signaled to all concerned. The Chief of Staff himself flew to Tokyo to raise the matter yet again. Again, to our great regret, no immediate decision to so equip the submarines was taken. The submarine crews in the forward area were longing for radar as farmers look for rain in a long drought. In theory submarines should refrain as much as possible from using their radar for fear of its being picked up by the enemy, and use instead a special receiving set for picking up the enemy’s transmissions. There were many, even among submarine captains, who subscribed to this theory, but the majority were in favor of the more positive method of using their own radar rather than depending on the comparatively few opportunities presented for picking up enemy signals. The latter method was a complete failure in the Kiska operations.
In actual fact, the only radar receiver fitted in our boats was one we had acquired from the Germans. Thus we had been reduced to rely on foreign tuition. What was the reason for such a disgraceful state of affairs? Was it due to a deficiency in our scientific knowledge and in our electrical industry? Unhappily this was precisely the case. Though we were poor, would it not have been better to have devoted more of our resources to scientific research? As we were deficient both in the bare necessities of life and natural resources, we should have diverted more of our national income into scientific research. Our scientific research policy was based on principles long since out of date—and the blindness of our submarines was the inevitable outcome. At Guadalcanal Island, U.S. aircraft would bomb a submarine on sight either by night or day without waiting to identify it. No doubt U.S. submarines with their up-to-date radar were confident of being able to submerge before being sighted by any aircraft. Thus a U.S. aircraft coming upon a submarine idly cruising on the surface would assume that it must be one of those deaf and blind Japanese! In our despair we were almost driven to the view that a single radar set would be of more value than a hundred submarines.
On May 15, 1944, I relinquished command of RO-44 just before she left Kure. My next job was to take charge of fitting out submarine I-58. I was due for about a month’s leave; but, not feeling the need for it, I instead devoted myself wholeheartedly to following up my ideas about radar. When I reported at the 6th Fleet H.Q., recently withdrawn from Truk, I came across a staff paper advocating the removal of the “useless” surface radar sets. To my astonishment the author of this fantastic opinion turned out to be the Admiral Commanding Submarines! In view of my early experiences with radar in I-58 I was very interested. I had heard nothing of more recent trials. As RO-44 had no radar, I was unable to refrain from commenting on the Admiral’s paper:
“It is premature to remove this useful equipment—indeed it would be a retrograde step. Why, when the set is fitted in submarines, is it regarded as useless, while the same set is still in use in surface craft? If further investigation shows that it really is valueless, then it can be removed. In my view, there is still plenty of scope for the submarine’s crew to improve the set’s performance, and I request therefore that the decision to remove the radar equipment be deferred until I-58 is completed.”
I then visited the personnel department of the Kure Naval Base and explained that the cause of failure in submarine electrical equipment was mainly due to the absence of skilled electricians in the crew. During the year and a half in which radar sets had been tried out, no high-grade electricians had been drafted to the submarines in question. After some argument I persuaded the personnel department to send me two expert electricians for I-58. Then I went round to the dockyard and, after carrying out exhaustive research with an experienced radar technical officer, we devised what we felt would be the best method for fitting this set into a submarine.
I-54-class submarine, equipped to carry Kaitens. I-58, the author’s command, was of this class. (Not to scale.)
At length I received orders to join I-58, and went to Yokosuka to take up my appointment. While I was going round the dockyard making myself known to the various officials, I urged all and sundry not to be late in fitting her new equipment. This involved the new method of fitting the surface radar set as well as one or two items concerning alterations to the machine-gun mounting. But in both cases the officials concerned, while expressing regrets, seemed unable to get the work done and I had to enlist the support of the Naval Technical Department and the Research Bureau to get things as I wanted them. Perhaps in my anxiety I hurt the dignity of the dockyard officials, but there was a war which allowed no time for haggling. In peacetime, one would have left everything to the dockyard staff, but in all the circumstances I have no regrets for my actions, for both my ship and I were in danger of being sent to the bottom. The dockyard officials at first refused to compromise over the manner of fitting the radar set, and I had further endless trouble before eventually getting them to install the equipment my way. The high-grade radar artificer promised by the personnel department took a long time in coming but eventually turned up in January after I had sent three hasteners on the subject. Apparently the signal school had tried to hang on to the man because they were short of instructors.
The battle for Saipan started while we were fitting out, and many of the submarines which went to operate there and off Guam failed to return. The fall of Saipan was a mortal blow. With it the air attacks on Tokyo began.
I-58 was approaching completion and we reached the stage of deep-diving trials. The normal safe diving depth was three hundred feet, but I-58 was designed to withstand the pressure of water up to four hundred and fifty feet. This was very necessary in wartime to evade depth-charge attacks. I-58’s diving trials were carried out to three hundred feet.
In diving trials a marker buoy was towed astern to indicate the boat’s positions and kept a check on her while submerged. First, measurements were taken in several places on the diameter of the pressure hull as she lay on the surface. Then the boat dived and measurements were continued every thirty feet to determine the extent of compression of the hull. Leakage points and discharge pump capacities were then tested and, all being well, I-58 surfaced, similar measurements being taken every thirty feet as she rose. Finally we had to ascertain whether she returned exactly to her pre-dive conditions, when she reached the surface.
In actual fact, on the first trial, a bad leak developed at two hundred feet, and the trial was abandoned, but the next day the trouble was put right and we started again. This time everything went without a hitch. Most of the naval training establishments were situated near Yokosuka and it was therefore a convenient locality for the training of submarine personnel. I had the lookouts and engine-room ratings put through special courses and the standard was very high.
In all I saw three submarines built during the war, and I was much struck by the greater efficiency of the private yards as compared to the naval dockyards, which didn’t seem to care how much time and money they wasted.
At length I-58 was commissioned and proceeded to the Inland Sea to join the training squadron for final working-up.
After the war the Americans said that the closest co-operation between air and surface vessels was essential in the efficient conduct of antisubmarine operations and that both should normally be centralized under a single command. The worst experiences that our submarines had to undergo was that of prolonged depth-charge attacks by destroyers and smaller vessels combined with bombing from the air. Such attacks were frequent subsequent to August, 1942, when the Americans began their night attacks using radar, for we had no means to counteract them. In fact from this time on we continued to suffer crippling losses from U.S. antisubmarine tactics, all through the battles of Makin and Tarawa and the latter half of the Solomons campaign in 1943 and the battles of Admiralty Island, Saipan, the Philippines, and Okinawa in 1944-45.
If a submarine remains submerged for more than forty hours it must surface long enough to change the air. Then, again, even though fully charged, batteries will not last longer than a similar period. When the boat has to dive with batteries not fully charged she cannot remain submerged so long. Success was sometimes achieved by remaining stopped and keeping at the required depth by taking in or pumping out a small quantity of water from the tanks—this, of course, economized in battery power. Nevertheless, the batteries would still eventually run down and many times our submarines were forced to surface close to the enemy. Sometimes our submarines were sighted while surfaced to recharge and would be severely depth-charged when crash-diving to escape. Some were saved by remaining down for a long period, but eventually most of them had to surface and fight it out with the waiting enemy. Sometimes there was insufficient high-pressure air for these emergency dives, and air had to be taken from the torpedoes. This meant the submarine was unarmed, for the high-pressure air cylinders used to fire the torpedoes couldn’t be refilled without surfacing.
Thus there was no method of overcoming this weakness whereby a submarine was compelled to resurface after forty hours, and in most cases the only boats to make their escape in these circumstances were those favored with the friendly protection of squalls or other natural aids.
The Americans achieved great success with their own submarines against ours. We were surprised after the war to hear the figures of losses inflicted by U.S. submarines. In fact, losses due to air attack were comparatively few. This was due perhaps to bad marksmanship by the aircraft—though the number of attacks was high, few hits resulted in fatal damage.