By S. Fukutome, former Chief of Staff, Combined Fleet, Imperial Japanese Navy
Prior to the attack on Pearl Harbor by our air units under the command of Vice-Admiral Nagumo, Japanese submarines were surrounding the island of Oahu and sitting astride the U.S. lines of communication between Hawaii and the American mainland. In addition, preparations were complete for sending five midget submarines to penetrate Pearl Harbor.
These submarines, comprising twenty-seven of the latest from the Combined Fleet Submarine Units, and under the command of Vice-Admiral Shimizu, sailed from Kure and Yokosuka between November 18 and 20, 1941.
After taking on fuel and provisions in the Marshalls they proceeded as the advanced guard of Admiral Nagumo’s striking force, with the primary object of cutting off ships of the enemy fleet which escaped the consequences of our air strike and, by stopping reinforcements and supplies from the U.S. mainland, so rounding off the whole of the Hawaiian operation. In fact the operations staff in Tokyo expected more from the longer-term submarine warfare than the momentary air strike. However, the results were entirely contrary to expectation and only one out of twenty-seven submarines was able to make any attack. Morison{24} in his history writes:
“Aggressive patrolling and depth-charging by destroyers and other ships on patrol completely nullified the work of the big 1,900-ton Japanese submarines. They did not torpedo a single one of the very numerous ships entering and departing from Pearl Harbor and Honolulu. Most of the twenty “I” boats deployed south of Oahu returned to Japan within a few days, but about five were ordered to the west coast of the U.S.A. One of these, I-170, was sunk by a plane from the USS Enterprise, en route, the others sank a few ships off California and Oregon. Thus the Advanced Expeditionary force failed completely. It inflicted no damage but lost all five midget submarines and one large one.
“Furthermore, when they returned to harbor after the operation, both the senior officers of units and captains of submarines reported as follows:
“‘The Hawaiian defenses are very sound and the enemy ships in general very much on their guard, making it impossible for submarines to enforce a blockade or cut the lines of communication. Enemy antisubmarine vessels and patrol aircraft kept up a relentless pressure and although our submarines did sight a few targets, they were counterattacked before getting a chance to put in their own attack.
“‘The submarine is a weapon for attacking merchant ships, i.e., its main function is commerce destruction.’
“Both Imperial Headquarters and the Combined Fleet were badly shaken by the results of the submarine operations at Hawaii and they were bitterly disappointed with their complete failure. As a result the faith of the Japanese Navy in submarines came to waver.”
In the first place Japan failed to secure her desired seventy per cent strength vis-à-vis America at the 1922 Washington Naval Treaty, but she calculated to make good this deficiency by means of submarine warfare.
Thus came into being the new tactical method peculiar to Japan—“Attritional Warfare.” That is to say, our policy was to use submarines to pick off units of the U.S. fleet as it made its way via Hawaii across the Pacific, and very far-reaching results were expected from such tactics. This policy was strongly advocated by Admiral Suetsugu who held that the success or failure of these tactics would be the turning point in the decisive battle between the two navies and he insisted on relentless training to this end.
In other countries the primary use of submarines was in attacking merchant ships and in commerce destruction, attacks on warships being a secondary object. This policy made the best use of the special features of the submarine and furthermore the loss of valuable cargoes to the enemy was considered of primary importance. Moreover attacks by submarines on closely escorted fleets were of a very hazardous nature. In Japan, however, the reduction of a heavily escorted U.S. warship fleet took precedence over all other targets and intensive training to this end was pursued, and there were frequent and lamentable cases of the sacrifice of submarines on peacetime maneuvers. Despite these occurrences the Japanese Navy went ahead with its plans to pierce the heavily escorted ranks of the enemy, and achieved the necessary confidence to attack warship targets. In fact there was a feeling of almost supernatural skill in the competence with which our submarines carried out their attacks in training and on maneuvers.
Under these circumstances the Japanese Navy expected much from their submarines and at the same time vastly underrated the capabilities of the American submarines. As the submarine campaign at Hawaii showed, our submarine attacks against warships completely misfired and the subsequent attacks on merchant ships achieved little. As opposed to this, our losses at the hands of U.S. submarines were very high and it would not be an overstatement to say that U.S. submarines dealt Japan a mortal blow. The following announcement was made by Ernest J. King, the Chief of U.S. Naval Staff. “U.S. submarines played a very big part in bringing Japan to submission—sixty-three per cent of Japanese ships of over one thousand tons were sunk by submarine, the remaining thirty-seven per cent being accounted for by the other armed forces.”
The figures estimated by the Japanese Navy for total shipping losses were 1,000,000 tons in the first year of the war and 800,000 tons in each succeeding year. In actual fact, however, the losses were as follows: First year, 1,250,000 tons; second year, 2,560,000 tons; third year, 3,480,000 tons, i.e., more than four times the estimated amount.
How did the Japanese Navy come to make such an inaccurate estimate? It was because they underestimated the U.S. submarines. Naturally enough the greater proportion of losses was probably expected to be inflicted by submarines, but the greater part of Japan’s sea lifelines lay along the routes to the areas of natural resources in the Southern Seas, comprising the Luchu Islands, Formosa, Philippines, Borneo, Celebes, Java, Sumatra, which were defended by a series of natural barricades. We had thought therefore that we could ward off the attacks of enemy submarines by our antisubmarine defenses in the comparatively narrow stretches of sea between these various islands. In the first year of the war alone, losses were heavy in connection with our southern advance and this was probably aggravated by the fact that our antisubmarine measures were undeveloped. But after the second year we might have expected a decrease in losses as our defenses were then in order, but the U.S. submarines proceeded to carry all before them.
Dr. Jerome Bernard Cohen wrote:
“The U.S. blockade of Japan increased in intensity, the supply of raw materials was cut off, and war production was virtually brought to a standstill before the strategic bombing commenced. For this reason Japan was unable to continue the fight....
“For every ton she built, Japan was losing three tons by sinking, thus setting at nought her merchant fleet. It was her reliance on the import of raw materials that brought Japan to the brink of misfortune. Matters progressed from bad to worse. The waste in shipping prevented the import of raw materials and steel production was thereby drastically reduced. This reacted on the shipbuilding industry and Japan was unable to make good her shipping losses, and she experienced economic strangulation. At the beginning of 1945 she was at death’s door and the air attacks supplied the finishing touches.”
The losses inflicted by U.S. submarines were not limited to merchant ships. The enemy proceeded to attack our warships with a quite unexpectedly efficient technique. Our losses were stupendous. On June 15, 1944, having heard that the U.S. forces had landed on Saipan, the C.-in-C. Combined Fleet, Admiral Toyoda, collected together all his available forces with the idea of counterattacking in a decisive battle and breaking up the enemy plans. One task force under the command of Vice-Admiral Ozawa began searching for the enemy from dawn on June 18 and by afternoon had sighted three groups of U.S. task forces containing six aircraft carriers to the west of Saipan. As the hour was late and the range excessive, he anticipated an action on the following day. At dawn on the 19th while carrying out a search he sighted an enemy task force in four groups, and at about 8 A.M. and 10 A.M., he launched the first and second attacks respectively. Vice-Admiral Ozawa’s flagship, the Taiho, was hit by torpedoes from an enemy submarine after launching the first attack and sank with a big explosion six hours later. The aircraft carrier Shokaku also was torpedoed by an enemy submarine at about the same time as the flagship. Vice-Admiral Ozawa, despite these losses, determined on a third air attack but there were less than a hundred aircraft remaining and that night he retired westward in expectation of action the next morning. On the afternoon of the following day, the 20th, he was attacked by three hundred enemy planes. The aircraft carrier Zuikaku was hit by several bombs and the carrier Hitaka was hit by torpedo bombers, and while drifting out of control she was torpedoed and sunk by an enemy submarine. Thus Ozawa’s squadron was picked off by submarines while engaged in air combat with the enemy task force. These carriers were strongly escorted by destroyers throughout the action, but the U.S. submarines penetrated our lines without any difficulty and carried out their attacks on large warships.
In October, 1944, Kurita’s fleet was intending to penetrate into Leyte Gulf to keep up the attacks on the enemy. On October 23, while on the lookout at the entrance to the Palawan Channel, the flagship Atago and the Nachi were sunk by a U.S. submarine, another very serious loss.
Furthermore there were many instances of U.S. submarines picking off even our antisubmarine vessels which were charged with the duty of affording protection from submarines. What were the reasons for these deplorable results? They were largely due to our inferiority in the fields of ordnance and ship construction. Our submarines, built and equipped with inferior weapons, were counterattacked by the enemy before they ever got to their targets, or were evaded. Against the superior equipment of the enemy submarines our ships under attack had no opportunity to counterattack or evade. Many of them were alive to the enemy’s presence only after they were attacked.
In the matter of building large-type submarines, Japan was in the lead among the world navies, and had built the two-thousand-ton I class as compared with the biggest in the American and British navies at fifteen hundred tons. Furthermore, during the war, Japan built some thirty-five-hundred-ton submarine aircraft carriers. On six occasions the superior I-class boats of the Japanese Navy were sent to Germany and while at the secret German submarine base of Lorient on the Atlantic coast of France, German submarine technicians made detailed inspections. The Germans criticized the excessive hull vibration and the excessive use of underwater signaling devices, etc., which were not conducive to the tricky conditions of underwater warfare. Submarine I-39, commanded by Commander Kinashi, was torpedoed and sunk by a U.S. submarine in the Formosa Strait on her return voyage from Germany. This was entirely due to inferior radar equipment. Captain Kinashi is said to have remarked when he put in at Singapore on this last voyage that he had no worry concerning enemy aircraft and submarines as the radar equipment had been greatly improved. On hearing of the many deficiencies in Japanese submarines, Hitler presented two German submarines to Japan to serve as models. One of them, with a German crew, arrived at Kure in July, 1943, but the other one was sunk in the Atlantic by Allied aircraft while en route to Japan with a Japanese crew. These German submarines were of the small seven-hundred-fifty-ton type and were therefore of little value to Japan.
The Japanese Navy expected much from its submarines, and for this reason alone both officers and men were carefully selected and put through the most rigorous training. They considered themselves superior in technique in the field of submarine warfare to any in other navies. But when it came to the test of actual warfare, the results were deplorable. At the end of the war, however, it can be said that slight improvements had been effected in the radar and other electrical equipment fitted in the Japanese Submarine Fleet.