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December 1941 – August 1945

Planned Submarine Attack on the Panama Canal:The Failure of Japanese Submarine Design: Wasteful Dissipation of Japanese Submarine Force:Japanese Submarine Cargo Missions to Europe: Japanese Submarines’ Disappointing ‘Kill’ Performance: Japan’s ‘Long Lance’ Jockeys: Newport Torpedo Station: Rear Admiral Charles Lockwood: US Submarine Achievements in the Pacific War: The Failure of Japanese Counter-Submarine Strategy: The Missed Opportunity.

The Planned Submarine Attack on the Panama Canal: In the summer of 1943 Commander Yasuo Fujimori conceived a plan with Captain Chikao Yamamoto to launch an attack on the Panama Canal with the objective of interdicting the flow of matériel from the US industrial heartlands on its eastern seaboard. Fujimori was a graduate of the Imperial Naval Academy in 1928. After a career serving in various capacities on submarines, he had been given command of RO-60 in June 1941. Later that year, two weeks after Pearl Harbor, Fujimori’s medium size L4 Type submarine, copied from the British L52 Type, and launched in 1922, was attacked by Lieutenant David Kliewer in his Wildcat fighter. In spite of its crash dive, Fujimori’s submarine suffered punctures to its diving tanks and periscope from two 100lb bombs. Fujimori quickly concluded that RO-60 could no longer dive safely. In January 1942 Fujirmori took charge of I-121, a largely obsolete Kiraisen Type mine-laying submarine based on a German design, before being sent to the Imperial Naval College where he graduated from ‘A’ Class. He joined the Imperial Navy General Staff in May 1943. Over the next 20 months his plan to attack the Panama Canal was developed in detail.

As a result, when Japan’s four submarine-aircraft carriers, two I-400 Class submarines and two modified A2 Type submarines, arrived at Nanao Wan on 5 June 1945 they found that the Maizuru Naval Arsenal had built a full scale mock-up of the Panama Canal’s Gatun Locks, the whole ‘triple flight’ that lowers ships 86ft before they navigate the passage into the Atlantic. The four submarines, I-400, I-401, I-13, I-14, were capable of carrying an aggregate of 10 aircraft; the Aichi M6A 1 Seiren sea-planes would bomb the Gatun Locks and, by Fujimori’s estimation, put the Panama Canal out of action for six months. It was a plan made possible by the development of Japan’s unique aircraft carrying submarines. First suggested by Admiral Isoroku Yamamoto, Commander in Chief of the Japanese Combined fleet, the I-400 Type had been conceived as a means of making attacks on US cities on their eastern and western seaboards. The plan called for the building of 18 such submarines although the eventual build was scaled back to just three. I-400 was laid down at Kure Dock Yards in January 1943; I-401 followed in April. I-403 was completed just five weeks before the end of the war and never made it to sea.

At 400ft long with a 39.4ft beam and displacing 6,560 tons, the I-400 Type was by far the largest submarine built by any nation in World War II. Its complement of 144 officers and crew was more than double that of the standard US fleet submarine, the Gato Class that was 311ft long with a 27.25ft beam and displacing 857 tons. Moreover the I-400 type was three times the size of the archetypal U-Boat. The Japanese behemoth was not exceeded in size until the US development of nuclear submarines in the early 1960s.

The I-400, with its pressurized hull, built with a unique figure of eight cross section designed to be strong enough to support an on-deck aircraft hangar, carried three Aiichi float planes with hinged wings that could be made combat ready in 45 minutes. The Aiichi Seiran bomber, a plane unknown to Allied intelligence until after the war, had a top speed of 295mph, a range of 650 miles and could carry an 800kg bomb. On top of the 102ft by 11ft cylindrical hanger that was integrated with the off-center conning tower were placed three 25mm cannon for anti-aircraft defense. A massive hinged, watertight door opened onto a 120ft ramp along which the Aiichi Seiran could be catapulted by compressed air. Lieutenant Atsushi Asamura, who was responsible for planning the mooted attack on the Panama Canal reported that the Aiichi Seiran, the only surviving example of which is displayed at the Smithsonian National Air and Space Museum in Washington, recalled that it was “a good performance aircraft. It was a versatile plane since it was both an attack bomber and had long distance range.”1

Lieutenant Commander Nobukiyo Nambu later noted, “I-401’s maneuverability under the sea was no different than other subs, though it had a greater turning radius on the surface.”2 As was the case with most Japanese submarines, the I-401 had a weaker hull than US submarines, and had a dive depth of 330ft versus 400ft for the US Balao Class. Remarkably the I-400 carried enough diesel gas to circumvent the world without refueling; it could make three trips to the US western seaboard without refueling.

However by the time that the aircraft carrier-submarines had assembled for their Panama Canal mission, Okinawa had fallen. As a result it was decided that it was too late to make a meaningful impact on the US supply lines. A disappointed Lieutenant Asamura noted that “I understood the importance of the Panama mission, but the US was on our doorstep and that was more imperative.”3 The Imperial Navy’s high command then toyed with the idea of dropping rats infected with bubonic plague and other diseases on the United States, a strategy that Unit-731, the Japanese Army’s human medical experimentation group, had used to considerable effect in Manchuria. But the plan was rejected by General Yoshijiro Umezu, Chief of the Army General Staff, clearly with an eye to Japan’s impending defeat, who thought that “germ warfare against the United States would escalate to war against all humanity.”4 Instead it was decided to use the I-400 force to attack American aircraft carriers at Ulithi Atoll.

The war ended before this attack could be carried out but not before I-13 was attacked and crippled on the surface by Grumman TBM Avengers as she was on her way to the Japanese island garrison on Truk. The I-400 surrendered to a US destroyer whose sailors were staggered by its size. Similarly when Commander Johnson, captain of the USS Segundo, a Balao Class submarine, took the surrender of I-401 he marveled at a Japanese submarine that was 25 per cent longer and displaced twice the tonnage of his own command. At 5am on 31 August 1945 Commander Nambu surrendered two Japanese samurai swords to Lieutenant JE Balson and a US flag was hoisted on I-401. The less compliant Captain Ariizumi shot himself in his cabin. Along with the large superfast I-201 and I-203, the aircraft carrier submarines, I-401 and I-14,were taken to Hawaii for inspection before being sunk when the Soviet Union demanded access to them.

Whatever their technological sophistication the carrier-subs were not comfortable at sea; a US seaman from USS Blenny who crewed one of the carrier-submarines back to Hawaii complained that “Because of the conning tower being off center to make room for the hangar they were very lopsided and bounced like a cork in rough seas. We started out in a terrific storm and didn’t serve meals for three days because almost everyone was seasick.”5

The Failure of Japanese Submarine Design: The fate of the three built Sentoku Type (I-401, I-402, I-403), the two Type AM (I-13 and I-14) and the three Sentaka Type (I-201, I-202, I-203) submarines, none of which ever saw action, is symptomatic of the failure of the Japanese submarine strategy in World War II. Japan produced technologically advanced submarines without ever designing a strategy to use them to maximum effect; their submarine strength was constantly dissipated in the pursuit of tasks for which they were not designed.

The I-400 and I-201 classes were in some respects the most advanced submarines built up until that date. The I-400, with its ability to cruise one and half times around the world and launch air strikes anywhere, anticipated the era of ballistic missile submarines first trialed by the Soviet Union in 1955 followed by the development of the first underwater-fired launchers with the USS Washington Class nuclear submarines in the early 1960s. As Dr. Hans Van Tilburg of the National Marine Sanctuaries in the Pacific Islands has observed of the similarly advanced carrier-submarine, I-14, which had also been designated for the Panama Canal mission, “the I-14 predates the cruise missile concept.”6

Meanwhile the I-201 Type anticipated the development of submarines that were genuine underwater craft rather than the typical Japanese and American submarines that were essentially surface vessels that could submerge. With a submerged top speed of 19 knots compared to 15.7 knots on the surface, the I-201 was slower only than the German Walter Type XVII. Tilburg noted that, ‘If you look at a sub like the I-201, it was nothing like anything in World War II… It had a streamlined body and conning tower and retractable guns. It looks more like a Cold War sub.’7

German technology had underpinned the rapid development of Japan’s submarines after World War I. Progress had been significantly aided by the acquisition through war reparations of seven German U-139 Type U-boats, which had almost succeeded in throttling Great Britain’s commercial lifeline. From 1931 Japanese technical abilities advanced to the point that they were able to start designing and building their own marine diesel units which previously they had had to import. Not included in the naval limitations treaties in Washington and then London in 1922 and 1930, the submarine was a maritime weapon that Japan could develop to the maximum. By the time that they entered World War II after the attack on Pearl Harbor, Japan had more varieties of submarine than any other nation; by the end of the war the Japanese fleet included not only aircraft carrier submarines but also miniature submarine carriers, cargo submarines, tankers, scouters, minelayers, midget (kohyoteki) and suicide submarines (Kaiten and Kairyu). Of 56 submarines displacing more than 3,000 tons in World War II, 52 of them were Japanese.

In addition to the profusion of submarines developed, Japan also produced the most destructive and famous torpedo of the war - the Long Lance Type 93. With the potency of their 63 submarines at the outset of the Pacific War, double the number available to the United States, it could have been expected that Japanese submarines would be a major contributor to Japan’s war effort. In the event, it proved to be the most disappointing service of their armed forces. After the war when Admiral Ozawa was interrogated about the poor performance of the Japanese submarine force, he answered that it was because “they did not develop their electrical equipment such as radar, sonic devices, and other equipment to the extent they should have. I think that is the basic reason for our poor showing.”8 Post war analysis was to show that poor electrical equipment was but one component in the failure of Japanese submarine operations.

Wasteful Dissipation of Japanese Submarine Force: Apart from the inefficient and bewildering profusion of weaponry in a force that boasted some thirty-nine different submarine types, Japanese submarine efficacy was blunted by the limitations put on their usage. At the outset of the war Admiral Yamamoto used his submarine force as an adjunct to the surface fleet. For the Japanese Navy, the submarine was primarily a fleet combat weapon rather than an offensive weapon aimed at disrupting the enemies’ commercial and economic strength. As naval historians Peatie and Evans have pointed out, the main conclusions drawn pre-war about submarines was their “vulnerability to detection by radio direction finding.”9 Unlike Germany the Japanese Navy did not use their submarines in wolf packs. Uniquely among the four major naval powers in World War II, Japanese submarines were commanded from shore; sea based command and control capabilities or tactics demanded by wolf pack operation were never developed. Although the Imperial Japanese Navy did recognize the possibility of commercial disruption, operational procedure emphasized the primary role of destroying enemy warships.

During the Pearl Harbor raid in December 1941 some 26 submarines were picketed around Hawaii with the aim of attacking any US ships that managed to escape the US fleet main harbor. In essence the Imperial Japanese Navy regarded the primary function of submarines as attack vessels in major fleet actions. As with the design of all of their fleet vessels, Japanese submarine design was predicated on the fighting of a single decisive fleet action.

Tactically, Japan’s Navy never acquired the correct balance between the need for stealth and attack. The emphasis was put on concealment and the patient waiting for the passing of capital ships before an attack was made from close quarters. Unlike the general preference of the Japanese Navy for attacking from long range, which the design of the Type-93 torpedo made possible, their submarine tactics advocated the principle of the sure-shot rather than firing from distance and escaping. After the war US Naval interrogators were astounded at the timidity of Japanese submarine tactics from a nation of the Banzai warrior: “It was frankly impossible to believe that [Japanese] submarines could spend weeks on the US west coast ‘without contacts’” one analysis recorded caustically, “or spend more than forty days among the Solomons during the Guadalcanal campaign without seeing any targets.”10 Given the exceptional courage of Japan’s military personnel, it seems likely that this overly cautious approach came from high command. Submarine expert, Norman Friedman, has stated that “The trade-off between preservation and combat effectiveness is central to submarine tactics and submarine design.”11 It seems that the Japanese Navy, in spite of its highly advanced torpedo and submarine design, failed to capitalize on these precious military assets.

Even the use of Japanese submarines as offensive assets against American capital ships changed after the Japanese reverse suffered at the Battle of Midway. Although the Kaidai Class I-168 finished off the badly damaged USS Yorktown after the battle and later in the year the USS Wasp, another fleet carrier, was sunk by B-1 Type I-19, this was the apogee of their success. As US carriers began to dominate the Pacific seaways, Japanese submarines were increasingly used as cargo carriers or troop transports. At the Battle of Guadalcanal, as the six-month engagement increasingly handed air supremacy to America, Japanese commanders increasingly resorted to using their submarines to supply or reinforce their troops stranded on the island.

Supply by submarine was hardly efficient. At Guadalcanal one of the larger submarines could carry only enough food to supply its Japanese forces for two days. By the time that the Guadalcanal conflict had ended, Japanese submarines had made 28 runs carrying an aggregate of 1,500 tons of supplies and munitions. To save space on the missions, crews were put on half rations. Two submarines were sunk. Up to September 1943 Japanese submarines also made 95 supply round trips from the southern HQ at Rabaul on New Britain to New Guinea. Just one submarine was lost in these operations. Not surprisingly Lieutenant Commander Zenji Orita protested: “using submarines for transport,” he complained, “is throwing away the reason for their construction.”12

When Japan’s main fleet was forced from Japan to Singapore in order to get closer to supplies of fuel, the Pacific was effectively surrendered to US control. When, after the Battle of the Bismarck Sea, air power started to shift even more rapidly toward the US, surface supply to New Guinea and Japan’s Pacific Island Empire became increasingly difficult. Not only supplies but whole regiments were lost as they transferred from China. Submarines increasingly became the only reliable way to sustain their military outposts. However, being reduced to missions as underwater supply and troop carriers was not conducive to fostering good morale in the submarine service. As Commander Nambu observed, “Subs were not meant be deployed as cargo carriers. Subs were meant to attack.”13

Even as supply vessels, submarines however were fighting a losing battle. US destroyers were not only increasing in numbers but by 1943 were receiving upgraded sonar equipment. Also the development of the Hedgehog, a forward throwing multiple mortar system, by the British Navy, which were adopted by the US as the Mousetrap proved even more effective than depth charges at killing submarines. (The Hedgehog took its name from the multiple spike spigots from which the mortar rounds were discharged). Forward throwing devices obviated the blind spot that destroyers had when they passed over a target before dropping depth charges from their rear racks. Japanese submarines were further disadvantaged by their size, their relatively slow submerging rate, and their lack of maneuverability.

In addition, the hulls of Japanese submarines were weaker than their American or German U-Boat counterparts. The thickly plated pressurized hull of a VII Type U-Boat would not rupture unless a lucky shot detonated within 4.6m. (In April 1945 the German U-427 survived 678 depth charges over many hours under attack). By contrast the US Mark 9 Depth Charge, introduced at the beginning of 1943 was devastating over much greater distances to the larger, less strongly hulled Japanese submarines which often provided a target double the size of a U-boat.

Knowing how deep to dive with the aim of avoiding destroyer depth charges was an unpredictable game of chance. Dive deep and a submarine was less likely to be hit. However the kill radius of a depth charge increased with depth because of the higher hydrostatic loading on hulls at lower depths. At near crush depth, any external detonation shock was more likely to cause catastrophic failure to the integrity of a submarine’s hull. By calculating the interval between the detonation bang of a depth charge and the powerful boom that followed, an experienced submariner might be able to calculate the depth, direction and distance of a depth charge and use the information to escape further attacks. However the most important requisite of a submarine commander was indubitably good luck.

As ground to air communication improved US carrier planes were able to join forces with destroyers; these tag tactics made search and destroy missions particularly successful. By 1944, with MAGIC intercepts also giving advance intelligence on submarine movements, the advantage in the undersea war had swung dramatically toward the US.

Built primarily as attack weapons, Japanese submarines’ design deficiencies became increasingly evident as the naval war turned in America’s favor. Large submarines were easier to sight visually. They were also slow diving, slow maneuvering, easy to track on sonar and were lacking modern radar of their own; their first sets were installed as late as June 1944 and were never comparable in quality to British and American technology. Lieutenant Commander Zenji Orita complained to Admiral Mito that “our chief weapon for detecting the enemy at present is 120mm binoculars. Top priority must be given to equipping First Class submarines with radar and electronic countermeasure devices.”14

Japanese Submarine Cargo Missions to Europe: The increasing vulnerability of Japanese submarines was displayed in their attempts to undertake cargo missions to Germany. After August 1943, when over the course of the previous 12 months only four out of 13 cargo ships reached Bordeaux, and only two out of 14 ships reached Japan, submarines became the only viable means of contact between Japan and her German allies.

Personnel and strategically important commodities were shipped to and fro. Products taken to Germany included gold for Japanese purchases as well as products needed by Germany including rubber, edible oils, quinine, tin, tea and coffee. I-8, a large pre-war submarine that carried a reconnaissance airplane, also took 48 crewmen designated to bring back U-1224 for purposes of reverse engineering. I-8’s famous voyage set out from Kure on 1 June 1943 and was completed with great fanfare in Brest after a two-month passage via Singapore. Key personnel such as submarine technicians were badly needed in Japan as were specialist products such as periscopes, optical products, electric torpedoes, sonar devices, scientific equipment and pharmaceuticals such as penicillin, some of which were required for human experiments on prisoners of war. I-8 also brought back Rear-Admiral Yokoi who had been naval attaché in Berlin since 1940 and Captain Hosoya, naval attaché to France. In addition three German officers and four radar hydrophone technicians made the return journey.

The mixed race voyages were not successful bonding exercises. A German passenger on I-8 complained that ‘The Japanese showed lack of understanding of the use of German canned food except fruits. The majority of it was thrown overboard. Fat was cut away from flitches of bacon and sausages were served cold etc. The Japanese crew showed free and easy homosexual behavior tolerated by the ships’ officers.’15

The following year the captain and crew of I-8 were principally responsible for the most noted submarine atrocities of World War II. After torpedoing the Dutch freighter SS Tjisalak on 26 March 1944, Commander Ariizumi made the 97 captured crew and passengers run the gauntlet of the Japanese crew who hit them with wrenches and sledgehammers and slashed them with samurai swords. They were then shot and thrown into the water. Six men managed to survive when they found a raft.

Two months later I-8 sank the Liberty ship, SS Jean Nicolet. Merchantman Carl Rosenbaum reported that the killing started when a Japanese officer hit 17-year old William Musser with a steel pipe before shooting him and throwing him overboard. Another seaman plunged a bayonet into the stomach of 19-year old seaman Richard Kean while another hit him over the head with a rifle butt and kicked him overboard. Commander Ariizumi harangued the other survivors: “You are now my prisoners. Let this be a lesson to you that Americans are weak. You must realize that Japan will rule the world. You are stupid for letting your leaders take you to war. Do you know that the entire American fleet is now at the bottom of the Pacific?”16 Some 23 men survived when the I-8 was forced to dive by an approaching aircraft. One of the men onboard was Francis J. O’Gara, a well-known sports writer on the Philadelphia Inquirer before the war. In memory of the supposedly deceased writer, a Liberty ship, SS Francis O’Gara, was named in his honor. After the war O’Gara was found in a Japanese prisoner of war camp and he was thus the only living person to have a Liberty ship named in his honor. Many of I-8’s crew died when US destroyers USS Morrison and USS Stockton sank the submarine off Okinawa on 31 March 1945. After the war three surviving crewmen were tracked down and imprisoned for war crimes. By then Commander Ariizumi had committed suicide.

Other submarines that made the trans-ocean journey to Europe had mixed fortunes. I-34 stopped in Singapore on 23 October 1943 and took on important stores including rubber, tungsten, tin, quinine, medicinal opium as well as samples of advanced Japanese weaponry. On 11 November, I-34 left for Penang to pick up passengers but was sunk in the Straits of Malacca by HMS Taurus, a British submarine sent to hunt her down after receiving American ULTRA intercepts. Just 14 of 94 men on board survived.

I-29, another B1 Type submarine, 356.5ft with a seaplane carrying capacity, managed to reach Mozambique with a cargo of gold; here she rendezvoused with U-180 where she took on board Subhas Chandra Bose, the pro-Japanese Indian leader who would subsequently take charge of the 40,000 troops of the Indian National Army fighting the British in Burma.

In spite of successful ULTRA intercepts, a second secret mission saw I-29, a B-1 Type submarine, commanded by the ace Japanese submariner, Takakazu Kinashi sail to Europe. On 15 September 1942 Kinashi had sunk the fleet carrier USS Wasp as commander of I-19 (another B-I Type) as well as damaging the battleship USS North Carolina and sinking the destroyer USS O’Brian in the same attack. I-29 arrived in Lorient in France on 11 March 1944 with a cargo of 80 tons of rubber, 80 tons of tungsten, 50 tons of tin, zinc, quinine, medicinal opium and coffee. Six RAF aircraft including two De Havilland Mosquito fighter-bombers narrowly missed destroying her off Cape Penas in Spain.

On the return journey, I-29, loaded with an Enigma coding machines, radar equipment, a rocket engine and a Messerschmitt Me-163, was attacked off Luzon Island in the Philippines by a taskforce of three US submarines, USS Tilefish (Balao Class), USS Rock (Gato Class) and USS Sawfish (Gato Class) which had sought her out after receiving ULTRA intercepts. I-29 sank after being hit by a spread of four torpedoes fired by USS Sawfish; only one crewmember survived. Captain Kinashi was among the dead.

The last mission to Europe by I-52, a Type C-3 cargo submarine replacement for the lost I-34, was taking gold, molybdenum, tungsten, rubber and coffee to France and was due to pick up 800kg of uranium oxide. After receiving intelligence, escort carrier USS Bogue and five destroyers led by Captain Aurelius Vosseller sought out I-52 and it was sunk by Lieutenant Commander Jesse Taylor’s Grumman Avenger Torpedo Plane. Having picked up the I-52 by radar travelling on the surface by night Taylor lit the Japanese submarine with flares and sank it with a well-directed torpedo-mine on 24 June 1944. All hands were lost. It was the last cargo submarine run to Europe. Captain Vosseller’s task force had sunk another Japanese submarine on 13 May 1944; in all, his group sank 13 Japanese and German submarines over an 18-month period to July 1945.

Overall the submarine missions to Europe were an expensive failure. From 1944 to 1945 some 2,070 tons of commodities and goods were shipped to Japan by submarine of which only 869 tons arrived. In the opposite direction just 611 tons of goods arrived out of 2,606 tons shipped. Plans authorized by Hitler on 18 January 1943, to build 20 XX Type cargo submarines to bring much needed metals and other resources to Europe, failed to materialize. By 1945 the tenuous links between the Axis powers were effectively stymied. The Allies would later conclude that “cooperation was never direct and at best the assistance rendered to each other was negligible.”17 In some cases help was denied. Japan was refused access to the technology included in the target searching acoustic T-5 Zaunkunig torpedo of the Kriegsmarine.

Japanese Submarines Disappointing ‘Kill’ Performance: Perhaps most surprising in the strategic direction of Japan’s submarine force, given the long distances over which the US needed to supply its forces as well as the scale of the matériel required, was that no concerted attempts were made to develop a strategy for the interdiction of the American supply chain. As Commander Fujimori’s plan to attack the Panama Canal indicated, there were officers within the Imperial Naval General Staff who at least understood the possibilities of disrupting US logistics. But, the omission of a consistent plan to disrupt US supply lines was astonishing.

During the course of the war, Japan’s submarine fleet recorded just 184 merchantmen sunk with a total tonnage of 0.9m tons. By comparison German U-boats sank 2,840 ships with an aggregate tonnage of 14.3m tons. The Americans, who started the war with a submarine fleet significantly inferior to that of Japan, sank 1,079 ships with a total tonnage of 4.65m tons while the British sank 493 ships with a total tonnage of 1.52m tons. In hindsight it seems remarkable that the Japanese submarine fleet did not prey on the vast commercial traffic as it approached Hawaii, New Zealand and Australia in the Pacific or indeed India where convoys brought supplies to sustain not only the British but also the Chinese armies. (See Appendix B: Oil, Raw Materials and Logistics.) A concerted effort to disrupt these supply lines in 1942 and 1943 would surely have reaped considerable dividends in the early stages of the ground battles in the Solomon Islands and New Guinea.

Having started the war with a considerable force of 63 submarines to which were added 111 completed during the course of the Pacific War, the Japanese Navy was not short of resources, at least not in the early stages of the conflict before losses and shortage of diesel began to take their toll on operational effectiveness. Out of a total of 128 total Japanese submarine losses, 29 were sunk in 1943 and 58 in 1944.

In part, the failure of Japanese submarines was because the Imperial Japanese Navy failed to develop a merchantman-killer that could be built cheaply and quickly on a mass-produced scale, as Germany achieved with the VII Type U-boat and America managed with the Gato Class. The most produced Japanese type was the Kaichu, which was categorized as a 2nd Class submarine; just 20 units were produced. Japan also produced 20 units of the B-1 Type, which was a 1st Class submarine; but at 356ft long and carrying a single plane it was far from being a low cost and fleet footed merchantman-killer. By comparison the United States built 77 Gato Type submarines and 128 of its updated successor, the Balao Type. Germany’s Kriegsmarine produced 703 VII Type U-boats which at just 220ft in length and 20ft in beam was by far the most successful merchantman-killer of World War II. As Churchill commented, “the only thing that ever really frightened me during the war was the U-boat peril.”18 In the Battle of the Atlantic, the U-Boat threatened the United States and Britain with defeat; Japanese submarines never remotely posed a similar threat in the Pacific. It can only be speculated on how different the outcome of the war might have been if the Imperial Japanese Navy had adopted a submarine strategy similar to that of Germany.

As late as mid-1943 Japan was laying submarine hulls that were highly advanced, technologically complex designs. I-400, I-14 and I-201 took over a year to build and test. Apart from I-13, which was sunk on its way to Truk, none of nine submarines from this group ever saw action. It was an effort that wastefully dissipated Japan’s limited industrial capacity. At the end of 1944, ever hopeful that they could “pull a rabbit out of the hat” with a new weapon that would win them the war, the Imperial Japanese Navy, virtually denuded of surface ships, pinned its hopes on yet another new submarine weapon development at the end of 1944.

Japan’s ‘Long Lance’ Jockeys: Inspired by the early successes of the Kamikaze pilots, two young seamen, noting the abundance of unused stocks of Long Lance torpedoes, conceived the idea of converting them into one-way rides for their suicidal jockeys. Commander Zenji Orita, who was stunned to discover that there were more volunteers for the special attacks than there were Long Lances was dismissive of this waste of human life. The relunctant Orita, who was ordered to deliver six Kaiten and their pilots to Ulithi Atoll was told in no uncertain terms by Rear-Admiral Kozo Nishina, 6th Fleet Chief of Staff, “The pilots have already been selected. All you have to do is to carry them close to the enemy and release them. The order comes from the top. You just follow instructions.”19 The six jockeys selected to pilot the Kaiten (heaven shaker) included Lieutenant Sekio Nishina, along with Hiroshi Kuroki, one of the pioneers of the Long Lance suicide submarine.

In the early hours of 20 November 1944, Orita, in command of the Type C2 I-47, a 356ft x 29ft beam submarine, took his six Kaiten passengers each ready to ride a 3,000 lb torpedo, to within a few miles of Ulithi Atoll. At 5.47am a huge explosion rocked USS Mississinewa, a huge 25,000 tons Cimarron Class replenishment oiler that had been launched earlier in the year at Bethlehem Steel’s Sparrows Point Shipyard in Chesapeake Bay; by chance the Mississinewa had replenished its tanks just a few days previously and was carrying 404,000 gallons of aviation fuel, 9,000 barrels of diesel, and 90,000 gallons of fuel oil. Subsidiary explosions lifted the ship out of the water and sent flames hundreds of feet into the air with a huge black pall of smoke spiraling miles into the sky. The tanker rolled over and sank at 9.00am. It was an initial successful result that, as with the kamikaze, flattered to deceive. Nothing was heard of the other Kaiten but the scale of the explosion led intelligence to falsely report back to Japan that several aircraft carriers had been destroyed. Some 400 Kaiten were produced in six different types but the only other confirmed success achieved was the sinking of a destroyer. The Imperial Japanese Navy’s final miracle weapon had failed.

Perhaps even more than the production of the wrong type of submarine, the failure of Japan’s submarine force can be blamed on strategic incompetence. In the post-war analysis it was felt that Japanese commanders shared a significant portion of the blame for the failure of Japan’s submarine strategies. Some ascribe the reluctance to attack merchantmen to it not being part of the Bushido code. However it seems likely that flagging morale, in a submarine force that was poorly directed and equipped, led to a disinclination to engage in combat. Further enlightenment is found in the extremely large number of times the target was ‘too far away to attack.’20 It seems that in post-war debriefing even the Japanese commanding officers could not disguise their embarrassment when faced with the bare facts of Japan’s submarine performance.

The wariness of the Japanese submarine commanders can also be attributed to the rapid development of the US destroyer force during the course of the war. At the outset the US was mainly dependent on World War I period four-stackers of the Clemson and Wickes Classes - some 273 in total. [The Clemson Class became famed for the Honda Point Disaster, an accidental beaching of 14 vessels off Honda Point, Santa, Barbara County, California, after the Great Kanto Earthquake produced extraordinary tides on the west coast of America, in the process disrupting the US fleet navigation systems.]

In the 1930s just 38 modern destroyers were produced from three classes of destroyer (Porter, Sims and Mahan). Although these vessels were being upgraded it took several years after Pearl Harbor for large quantities of new destroyers to come on stream. It was evident in the earlier phases of the war, particularly in the Battles of the Slot at Guadalcanal, that US destroyers were outperformed by their Japanese counterparts. After 1943 however, a vast new influx of fleet destroyers were delivered to Asia. Apart from 92 fleet destroyers of late 1930s design (Benson and Greaves Class), US shipbuilders delivered a staggering 233 Fletcher and Sumner Class destroyers by the end of the war. In addition to fleet destroyers, the US also deployed 377 new, slower Destroyer Escorts by the end of the war: Evarts Class (65), Buckley Class (65), Cannon Class (58), Edsall Class (85), Rudderow Class (21) and Butler Class (83). With the exception of the Evarts Class, all these new Destroyer Escorts used newly developed steam powered turbo electric drives developed by General Electric, or innovative combined speed turbines built by Westinghouse.

Ineffective 1.1-inch anti-aircraft cannons were also replaced by the now standard US re-engineered Bofors 40mm weapon, which proved so effective during World War II. Added to their racks of Mark IX depth charges, forward throwing Hedgehogs and uprated sonar and radar, the Bofors made the new Destroyer Escorts into superb defensive weapons for convoy duty. At the peak of the Pacific War in mid -1943, the US Navy had orders for some 1,005 escort destroyers alone; although this requirement was later scaled down, nevertheless the US shipbuilders delivered an aggregate total of 557 Destroyer Escorts and conversions by the end of the war.

Deploying sonar and radar capabilities far in advance of their Japanese counterparts, the arrival of new US destroyers during the second half of the Pacific War simply overwhelmed Japan’s submarine forces with both their numbers and their technology.

Newport Torpedo Station Scandal: If Japan’s submarine force performed poorly in the Pacific War, the US submarine force’s performance was equally lamentable, perhaps worse, in the first eighteen months of the conflict. “We had the greatest concentration of submarines in the world,” recalled war correspondent Hanson Baldwin, “but we didn’t do a thing!”21

In the initial phases of the Pacific War the main problem for Nimitz and his submarine force was that there were just fifty-three mainly obsolete S-Class American submarines in the whole of the Pacific region. With the Battle of the Atlantic in full flow the priority for supply of new submarines was the war in Europe. With the need to supply both Great Britain and Russia, Germany’s U-Boat posed a credible threat to the logistical chain that kept America’s allies in the war.

What submarines were available to the US in the Pacific were ordered to Brisbane, Australia after the fall of the Philippines. Captain Ralph Christie, stationed in the Atlantic with S-Class submarines was ordered to join them and set up a command base. Under his direction US submarines were designed mainly as scouts. It was a strategy in keeping with pre-war orthodoxy. Pre-war training had over-emphasized the ability of planes and destroyers to track down submarines using sonar. By contrast Nimitz’s submarines based in Hawaii were ordered to target Japanese capital ships.

Leadership was also a problem. Until the development of wolf-packs (groups of submarines) each submarine operated alone and depended heavily on the skill and determination of its commander. When war arrived, it was found that a high percentage were not up to the job. During 1942 alone Admiral Lockwood removed 30 percent of all submarine commanders. The removal rate fell to 7 percent per annum in the following two years. Unlike in the German Navy, US commanders were not trained in nighttime attack from which their enemies had yielded good results. Furthermore the standard training manual recommended sound (sonar) attacks rather than sight attacks using periscopes. The latter was a far more reliable system.

As a result, in the first eighteen months of the war, the US submarine fleet was anything but successful. But the main reasons for this was neither strategic nor due to poor leadership. It became quickly apparent that the Mark XIV torpedo did not work. In Brisbane, Christie, whose S Class submarines were still using the Mark X torpedo of World War I vintage, disputed the causes of the failure of the new torpedo. Perhaps this was not surprising as Christie, after graduating from the Massachusetts Institute of Technology with a degree in Mechanical Engineering, joined project G-53, which the Bureau of Ordnance had initiated to develop a magnetic exploder for torpedoes. The German Navy had developed magnetic mines in World War I and in the post-war period both Britain and Germany further developed magnetic devices. By firing a torpedo to explode underneath the hull of an enemy ship, a powerful gas bubble would force itself upwards and rip apart the hull at a point that was weaker than the more heavily plated sides of an enemy warship.

Having developed the Mark VI magnetic exploder, Christie, at the Newport Torpedo Station, was also involved in the design and manufacture of the Mark XIV torpedo to carry the new exploder. Remarkably, because of obfuscation by the Navy Department, the Mark VI exploder and Mark XIV torpedo were never live tested before they were put into service. One of the reasons for this was the tiny production volume of the Mark XIV. Submarine captains were ordered to hold back on firing spreads (numbers of torpedoes fired in a spread pattern) on targets because of the shortage of stock – a problem that had been massively exacerbated by the monopoly that Newport Torpedo Station exercised on the production of torpedoes and the antiquated hand-built production techniques that they employed. The result of protective monopolistic practice and outdated manufacturing processes was that in 1941 each torpedo cost US$10,000 (US$150,000 in 2015 terms). Small wonder that Newport did not live-test their products.

After reports that the Mark XIVs were running too deep, Christie, in Brisbane, disputed the extent of the problem and blamed malfunctions on poor maintenance and operational mistakes. Submarines were ordered to persist with the Mark XIV. Much to his annoyance in November 1942, Christie, promoted to the rank of rear-admiral, was ordered to return to Newport as Inspector of Ordnance, to solve the problems of manufacture and reliability. It did not help that officials at the Newport Torpedo Station, in attempting to cover the tracks of their incompetence, consistently lied about the issues of depth setting and the non-working of both magnetic and contact exploders.

Almost uniquely with regard to American weapons procurement, the Navy was its own supplier. On the grounds of security Newport Torpedo Station fiercely protected its monopoly position. It was protected by the Bureau of Ordnance, known as BuOrd, whose power, supported by Congressional influence, notably from Rhode Island’s legislators, was largely untouchable by the Navy’s top commanders. Even when Admiral Charles Lockwood managed to get experienced submarine officers appointed to Newport, they were ignored. An exasperated Lockwood wrote to Rear-Admiral William ‘Spike’ Blandy, Newport chief, to get BuOrd “off its duff (buttocks).”22 Later revelations showed that it was a corrupt self-serving bureaucracy. It was only when Admiral King in Washington took a direct interest in the matter and appointed the Navy Inspector General’s office to investigate BuOrd and Newport in 1943 that major changes began to be made.

Remarkably Newport’s commanding officer, Rear-Admiral William ‘Spike’ Blandy’s career was unaffected by the disastrous Mark XIV torpedo episode which not only disadvantaged US submariners but pointlessly sacrificed the lives of torpedo crews at the Battle of Midway. It was a scandal that was largely covered up until after the war. Full attention only came to the scandal and its cover-up after publication of World War II submariner, Clay Blair’s Silent Victory: The Submarine War Against Japan [1975].

President Roosevelt was never drawn into the internal conflict. He had unfortunate history with regard to Navy affairs in Newport. In March 1919, Roosevelt, then Secretary of the Navy, had ordered an investigation into institutional naval homosexual practice centered on the Army and Navy YMCA and the Newport Art Club. After a three-week trial in which thirteen sailors were found guilty of sodomy, Roosevelt came under attack for the methods used by the investigators and ultimately resigned his position. He was subsequently reprimanded by a US Senate Committee.

Rear-Admiral Charles Lockwood: At the main Pacific US submarine base in Brisbane, Christie was replaced by Captain James Fife. At this point fate intervened to change the course of the submarine war. In January 1943 Rear-Admiral Robert English, Commander of the renamed Submarine Force, Pacific Fleet, based in Hawaii was killed in a plane crash. Not only was Christie overlooked for the top job that was given to Rear-Admiral Charles Lockwood, but he was ordered to return to the Pacific to take over Lockwood’s former command at Fremantle, a smaller command than his former post at Brisbane, which had been put under the command of Fife. In effect Christie had been demoted in the command reshuffle. He lobbied unsuccessfully with MacArthur’s HQ to have Fife’s Brisbane command put under his control.

Christie became a disaffected element in the management of submarine operations in the Pacific and soon clashed with Lockwood over use of the Mark VI magnetic exploder. Convinced by reports from his submarine commanders that the Mark XIV torpedo was not working, Lockwood ordered the magnetic exploder to be deactivated – an action that the maverick Commander Dudley ‘Mush’ Morton had already done on his own initiative. Morton, the heavy jawed Commander of the USS Wahoo became the most famous US submarine commander of World War II. Having taken command of the Wahoo on 31 December 1942, he went on to become the submarine service’s first ace. In four offensive missions over the next nine months, he sank nineteen Japanese vessels aggregating 55,000 tons.

His maverick methods became legend. In a foreword to crewmember Forest Sterling’s book Wake of the Wahoo, a 1960 account of Morton’s career, Admiral Lockwood wrote: “When a natural leader and born daredevil such as Mush Morton is given command of a submarine, the result can only be a fighting ship of the highest order, with officers and men who would follow their skipper to the gates of hell… and they did. Morton lined up an impressive number of ‘firsts’ during the short nine months that he commanded Wahoo: first to penetrate an enemy harbor and sink a ship therein; first to use successfully a ‘down the throat shot’ (straight-on bow attack); and first to wipe out an entire convoy single-handed.”23 Morton, Lockwood’s favorite captain, was killed when USS Wahoo, on a mission to penetrate the Sea of Japan that divides Korea and Russia from Japan, was sunk by depth charges dropped by a Japanese aircraft in the Soya Strait (La Perouse Strait) between the Russian Sakhalin Island and Hokkaido, Japan’s northernmost island. The loss of Morton on 11 October 1943 was a particular blow to Lockwood who had initiated the mission to penetrate Japan’s inner sanctums; he would later write in his autobiographic account of Operation BARNEY that “I resolved, there would come another day - a day of visitation - an hour of revenge.  In time we would collect for the Wahoo and Commander Dudley Walker Morton and his men, with heavy interest. And in time we did.”24

In Fremantle, Christie ignored the order to deactivate the Mark VI. He only complied when ordered to by Vice-Admiral Thomas Kinkaid when he became MacArthur’s new Commander Allied Naval Forces. Perhaps more importantly Christie further fell out with Lockwood over the loss of USS Harder. After sinking five destroyers in the Celebes area during the 5-week voyage of his fifth patrol, Harder’s captain, Dealey, returned to Fremantle. Against all acceptable conduct, Rear-Admiral Christie promptly ordered Dealey to take him out for the experience of going on a live patrol. It was a highly irregular request and, given his position of command, peculiarly irresponsible. Having missed out on two known targets, a cruiser and a cargo ship laden with nickel, Dealey returned to base after this week-long addition to his fifth patrol.

After two weeks rest, his executive officer, ‘Tiny’ Lynch, considered that Dealey was still too tired to command. However Dealey, who Christie had already tried to persuade to step aside, was adamant that he needed to train new crewmen. He set out on a new patrol, his sixth, and, while in partnership with Captain Chester Nimitz Jr. commanding the USS Haddo, USS Harder was sunk by a Japanese minesweeper on 24 August 1944 losing all hands on board. The episode led to a further estrangement of Christie and Lockwood.

Eventually, Admiral Kincaid sacked the troublesome Christie after disputes over the award of medals to Dealey and ill-feeling over the death of Kinkaid’s nephew, Lieutenant-Commander Manning Kimmel on the Fremantle based USS Robalo, which was sunk in July 1944. Christie spent the remainder of the war as commander of Puget Sound Navy Yard. As for Commander Dealey, who with 16 kills of an aggregate weight of 54,000 tons to his name, making him the fifth most successful US Pacific War submarine ace, he was posthumously awarded the Silver Star Medal for gallantry.

He also won the Medal of Honor, the Navy Cross with three gold stars; Dealey’s citation read, “For conspicuous gallantry and intrepidity at the risk of his life above and beyond the call of duty as Commanding Officer of the USS Harder during her 5th War Patrol in Japanese-controlled waters… This remarkable record of five vital Japanese destroyers sunk in five short-range torpedo attacks attests the valiant fighting spirit of Comdr. Dealey and his indomitable command.”25 More controversially Dealey was awarded the Army’s Distinguished Service Cross by General MacArthur for service in his theater of the Pacific War.

Dealey was not the only submariner to become an inspiring hero in the early phases of the submarine war. In February 1943 Commander Howard Gilmore, captain of USS Growler (Gato Class), having already sunk a freighter on his fourth patrol, rammed an approaching Japanese gunboat and sank it. However Gilmore and his crewmen were raked by gunfire and the wounded captain, unable to reach the hatch, shouted out ‘take her down’, words that became part of World War II submariner folklore. Gilmore’s citation for the Medal of Honor read, ‘In the terrific fire of the sinking gunboat's heavy machineguns, Commodore Gilmore calmly gave the order to clear the bridge, and refusing safety for himself, remained on deck while his men preceded him below. Struck down by the fusillade of bullets and having done his utmost against the enemy, in his final living moments, Commodore Gilmore gave his last order to the officer of the deck, “‘Take her down.’ The Growler dived; seriously damaged but under control, she was brought safely to port (Brisbane) by her well-trained crew inspired by the courageous fighting spirit of their dead captain.”26

Meanwhile Lockwood spent the early months of 1943 wrestling with the problems of the Mark IV torpedo. The magnetic exploder was not the only fault. A design flaw caused US torpedoes to run too deep. Even the contact exploders malfunctioned; it was found that torpedoes fired at ships at the perfect square-on 90-degree angle did not explode. Indeed ships arrived in port with Mark XIV torpedoes buried in their flanks. Submarine commanders found that more difficult glancing shots worked better. Frequently the Mark XIV also failed to run true and commanders often failed to hit targets at close range. Some torpedoes ran a full circle. On 25 October 1944, USS Tang, a Balao Class submarine, under the command of veteran submarine ace Lieutenant-Commander Richard O’Kane, who had sunk 33 Japanese vessels in his first 11 months of service, was sunk by its own torpedo, which boomeranged back.

O’Kane was one of nine surviving crew to be picked up by a Japanese destroyer on which they were beaten up by survivors from USS Tang’s earlier victims. O’Kane would graciously write in his autobiography Clear the Bridge! The War Patrols of the USS Tang [1977], “When we realized that our clubbing and kickings were being administered by the burned, mutilated survivors of our handiwork, we found we could take it with less prejudice.”27

It was not until the autumn of 1943 that Lockwood, largely by the efforts of his maintenance engineers in the Pacific, managed to adjust the Mark XIV mechanisms enough to make it a workable weapon. Lockwood himself, realizing the importance of the torpedo issue, oversaw many of the torpedo trials himself. Lockwood known to his devoted sailors as ‘Uncle Charlie’, Lockwood became a highly successful commander, arguably one of the most important albeit least known senior commanders of World War II. Lockwood dismissed ineffective submarine commanders, redirected strategy toward the sinking of Japanese merchantmen and tankers and the interdiction of supply to Japan. Lockwood also introduced new rotas to ensure the health and recuperation of crews who would often have to endure five or six-week missions on iron rations after their submarines’ supplies of fresh food ran out.

An experienced submarine commander, he never forgot that conditions of life on a submarine were appalling. In World War II submarines the accumulated stench of human sweat and diesel oil penetrated every artifact. Apart from the appalling food, submarines were infested by insects. One submariner noted, “When we did not have battle, we spent our time to catch and kill cockroaches. We had some rats too. One time when oxygen in the submarine became so thin, we found many rats who could not run because of lack of oxygen. We easily caught many rats.”28 Captain William Ruhe of the USS S-37 complained that cockroaches “prowled around and over us at all hours.”29 Apart from the difficult conditions, that matched anything suffered by troops in the jungles of south east Asia, the mental strain of patrols that could last for fifty-six days or more was equally debilitating. When under attack, the fact that a submarine in World War II was little more than a submerged coffin, must have constantly gnawed at the minds of its submariner combatants.

US Submarine Achievements in the Pacific War: Within six months of his taking command of submarine operations in the Pacific War, Lockwood’s forces’ record of performance took a dramatic upward turn. In the first three months of 1943 US submarines sank 57 Japanese merchantmen. By the last quarter of the year the tally had risen to 106, accounting for 65 percent of Japanese merchant ships sunk in that period. In the following quarter, January to March 1944 US submarines sank 136 merchant ships with an aggregate weight of 500,000 tons.

As well as improved torpedoes and operating procedures, Submarine Force, the US Pacific Fleet’s force, was the recipient of an increasing supply of new submarines: the Gato Class and its up-dated successor, the Balao Class. The 312ft by 27.3ft beamed Balao Class with up-rated thick steel and doubled-hull, had more powerful diesel engines and batteries that enabled it to carry out the long range, long duration missions required in the broad reaches of the Pacific Ocean. New submarines delivered increased from 39 in 1942 to 50 the following year and 80 in 1944.

USS Balao would later star as the pink submarine in the Blake Edwards comedy movie Operation Petticoat [1959] with Cary Grant, Tony Curtis and Joan O’Brian, and Pacific submarines would feature in another post-war movie. In June 1945, Lockwood sent nine submarines into the Sea of Japan via the Straits of Tsushima supposedly to test the effectiveness of a new FM sonar in locating minefields. The Operation Barney expedition sank 28 boats (58,000 tons) but USS Bonefish was lost with all hands. It was later questioned whether the operation was justified. Some suspected that it was a revenge mission for Lockwood’s favorite commander ‘Mush’ Morton while others have argued it was a statement of intent to the Russians that the US intended to control the Sea of Japan after the war. However Lockwood may simply have wanted to kill merchant ships and to get across the message to Japanese leaders that nowhere was safe from the US Navy. Operation Barney would later feature as a movie, Hellcats of the Navy [1957] starring future President Ronald Reagan and his wife Nancy Davis (her screen name). It was the only movie they made together.

A record monthly submarine tally of 68 ships was achieved in October 1944, a month in which 130 Japan merchant vessels were lost. Adding to the ravages of submarines, Nimitz’s patrolling fleet task forces in the South China Sea, combined with the Army Air Force now based in the Philippines, were increasingly joining in the wholesale destruction of the Japanese Merchant Fleet. By the first quarter of 1945 US submarine kills on merchantmen, 60 in total, had fallen back to the levels of the first quarter of 1943. Noticeably in this quarter US submarine tallies represented less than 30 percent of Japanese vessels sunk; as the US surface fleet began to surround Japan, it increasingly began to interdict Japanese coastal traffic as well as merchant ships making the short crossing of the Sea of Japan from Korea. The mining of the key straits guarding the Inland Sea and the Kanmon Straits between Kyushu and Honshu, further added to the misery of Japanese marine traffic. In aggregate, in the course of the Pacific War, US submarines sank 4.8m tons of merchant shipping representing 55 percent of their total losses. Having started the war with 6m tons of shipping, and in spite of building 3.25m tons, Japan ended the war with less than 2m tons of which only 312,000 tons was considered to be still serviceable. Unarguably Lockwood’s Submarine Force was the major single contributor to the economic strangulation of Japan.

For the loss of 52 submarines and 348 officers and 3,136 crewmen killed, the US submarine force probably represented the best return on investment of any service in the Pacific War. An aggregate of 1,392 Japanese naval and civilian ships were sunk achieving an average rate of 0.8 kills per submarine patrol. US submarines were perhaps fortunate that Japan was slow to develop destroyer protected convoy systems; as was typical of much of Japan’s planning, defense systems and technology were largely sacrificed to offensive weaponry.

Albeit smaller than their Japanese counterparts, US submarines’ hulls were better designed and more capable of withstanding depth charges. In this respect, they were also helped by the fact that Japanese depth charges carried relatively light charges; Type-95 was standard at the time war broke out, with a 100kg charge of Type-88 explosive, (ammonium perchlorate and ferro silicate). Also, at least in the early part of the war, Japanese depth charges tended to be set too shallow as the Type-95 had just two settings at 100ft and 200ft compared to the standard diving depth achievable by US submarines which was usually 300ft. Lockwood’s Submarine Force was helped by the fact that Japanese destroyers in the pre-war period had largely been designed as fleet attack weapons rather than defensive anti-submarine weapons.

The Failure of Japanese Counter-Submarine Strategy: At the start of the Asia Pacific War, the Japanese Navy was equipped with some of the best attack destroyers of the war. The first Fubuki Class destroyer launched in 1926 set a world class standard for its speed and weaponry. Apart from the top heavy Hatsuhara Class destroyer, designed to comply with the 1930 London Naval Treaty, the Japanese Navy produced a series of superb destroyers; the Shiratsuyu Class was a quickly developed re-design to correct the problems of the Hatsuhara Class. However when Japan allowed the 5-year provisions of the London Naval Treaty to lapse, the Asashio Class destroyer was developed with a speed of 35 knots and a range of 10,600km. It could also carry six 127mm naval guns as well as up to 28 Type 96 AA guns, 16 torpedoes and 36 depth charges.

Further offensive destroyers were developed with the Kagero Class, the Yugumo Class and Akizuki Class destroyers that were introduced between 1939 and 1942. Armed with Long Lance torpedoes, these Japanese destroyers became feared offensive weapons. But they had shortcomings. Apart from the weakness of their radar systems, the main concern was their over-sophistication. They were also designed to fight as auxiliary offensive vessels in large surface actions. By the end of 1942 it became clear that this was not the pattern of naval warfare that could now be expected. As aircraft came to dominate naval engagements, Japan’s overly complex destroyers were exposed as weapon systems that were too costly and time consuming to build.

By 1942 the Imperial Japanese Navy realized that it needed mass-produced destroyers of a lower specification and with greater emphasis on anti-aircraft artillery for the protection of fleet carriers, and more depth charges for deployment against US submarines. The result was the development of the Matsu and Tachinbana Class destroyers that were slower with a speed of 27 knots but carried more anti-aircraft and depth charge firepower. However by the end of the war only 42 out of 122 vessels planned had been built.

Perhaps not surprising in view of the offensive mentality of Japan’s Navy, the attention paid to convoy strategy and protection was de minimis. Despite the urging of Navy Chief of Staff, Admiral Kanji Kato, in a memo written in 1929 regarding the importance of protecting sea-lanes, scant attention was paid to this aspect of any future war. Experts within naval intelligence, such as Lieutenant-Commander Atsushi Oi, who had studied the British convoy system in 1939, were ignored by their superiors. The issue was also raised by the Cabinet Planning Board in 1941 but was deflected by Admiral Osami Nagano’s bland assurances that the Navy was dealing with the problem of bringing “American submarines under control.”30 Until late in the war there was no convoys plan or any one naval or military authority in sole charge of organizing the protection of foreign supply - an extraordinary oversight given that access to commodities, particularly oil, was the casus belli. It was an oversight that Germany’s naval attaché in Tokyo, Vice-Admiral Paul Wenneker, found particular irksome. He recorded that he “suggested the desirability of attacking the route between Honolulu and the West Coast because that would force the use of convoys and would force the withdrawal of many escorts from the western Pacific.”31 Wenneker organized for a full submarine crew to be sent to Germany for special training on German attack methods but on the return journey their submarine was sunk.

Reflecting this oversight on convoys, at the start of the Pacific War, Japan had a paucity of escort destroyers or Kaibokan (ocean defense ships). These vessels, designed to travel at less than 20 knots because they were protecting slower moving cargo ships (10 -15 knots) were armed primarily with depth charges (up to 300) and anti-aircraft guns. For the whole of Japan there were just four Shimushu Class escorts and a smattering of older vessels. Of their successors that were commissioned after the outbreak of war, the Etorofu Class had just 14 ships built while of the later planned mass-produced Ukuru Class there were only 29 built of the 142 planned. It was too little, too late.

Lockwood’s forces were also helped by the paucity of Japanese sonar devices and their failure to develop forward throwing mortar depth charges. Unlike their Japanese counterparts, US submarines were all fitted with SD non-directional anti-aircraft radar by the end of 1942. US submarines were also equipped with SJ surface radar by the end of the following year. As well as providing accurate direction radar information regarding incoming aircraft, even when they were low flying, SJ radar could send point-to-point signals between submarines operating in a wolf pack. Revolutionary PPI (Plan Position Indicator) screen technology was also introduced. As for periscopes, Lockwood’s Submarine Force was up-rated in 1944 from which time periscopes were manufactured with range finding ST, SD or DSJ radar built in. This enabled target distance evaluation without the need of a sonar’s ping, which could give away a submarine’s whereabouts.

Although the sinking of Japanese merchantmen was the US Submarine Force’s major contribution to the Pacific War, US submarines also accounted for the sinking of four Japanese carriers including Shinano (the world’s largest carrier, built on a keel laid for a sistership to the Yamato and sunk on her maiden voyage), Shokaku, Taiho and Unryu, as well as four escort carriers: Chuyo, Jinyo, Otaka, and Unyo. Submarines also sank a battleship (Kongo), along with four heavy cruisers (Atago, Kako, Mayo and Ashigara) nine light cruisers (Agano, Izuzu, Nagara, Natori, Oi, Tatsuta, Tenryu, Yubari and Tama) 38 destroyers and 23 submarines. Some US submarines achieved astonishing records; USS Flasher, a Gato Class submarine launched in June 1943, alone sank 100,231 tons of Japanese shipping while USS Tautog, a Tambor Class submarine that operated throughout the entirety of the Pacific War, sank a record 26 ships.

While economic strangulation of Japan became the key task of Submarine Force, on numbers of occasions US submarines also destroyed key Japanese personnel. On 8 May 1942 USS Grenadier (Tambor Class) sank the 14,500 ton Taiyo Maru off Kyushu killing hundreds of Japanese scientists and technicians heading south to take on the task of resource management in Japan’s newly acquired empire – particularly its oil assets. In April 1944, Japan’s bid to reinforce its defenses in western New Guinea was disrupted by the sinking of Yoshida Maru by USS Jack (Gato Class), which drowned an entire Japanese regiment on its way from China.

At the end of the war submarines also destroyed thousands of small craft. On a single patrol USS Blenny (Balao Class), under the command of Lieutenant-Commander W.H. Hazzard, sank 63 Japanese trawlers, sampans and other small craft by gunfire or with hand grenades. Many of the Blenny’s targets were sunk by surface attack using their 5-inch deck-gun that, along with up-rated machine guns, was a typical up-grade towards the end of the war. As carrier aircraft increasingly took up the task of destroying Japan’s remaining merchant fleet and bombing the mainland, submarines took up a new role of rescuing airmen. 380 airmen were rescued in 1945.

It was a record that did not receive due acknowledgement at the time. Inevitably security required that America’s submarine force was a silent service. The cost of not being silent became a stark reality when Kentucky Democrat Congressman Andrew May, after a briefing during a press junket to the war zone, revealed that Japanese destroyers were underestimating how deep US submarines could dive with the result that they were setting their depth charges too shallow. May revealed this information at a press conference, which immediately became public news, leading the Japanese submariners to reset their charges. An incredulous Lockwood wrote sarcastically to Admiral Edwards: “I hear… Congressman May… said the Jap depth charges… are not set deep enough… He would be pleased to know the Japs set’em deeper now.” After the war Lockwood estimated that the ‘indiscretion cost us ten submarines and 800 officers and men.”32

Indeed Japan’s later depth charges were increased to 147kg (from 100kg) of Type-97 explosive (70 percent TNA/30 percent HNDA) and a 300ft setting was introduced. When Japan introduced the Type-2 depth charge that carried 105kg, they significantly increased the weapons flexibility closer to British design, with detonation settings at 98 feet, 197 feet, 292 feet, 390 feet, and 480 feet. After the war Democrat Congressman Andrew Jackson May was convicted of bribery charges relating to payments for munitions contracts while he was Chairman of the House Military Affairs Committee during the war.

Fortunately for Lockwood’s Submarine Force, changes to Japan’s depth charges took place too late to have a significant impact on the war. In total just twenty-two US submarines were lost to depth charges. By comparison, depth charges accounted for eighty-five kills of Japanese submarines.

The Missed Opportunity: In reviewing the operation of Japanese submarines during the Pacific War, it is difficult not to come to the conclusion that Japan missed a major opportunity. The Washington and London Naval Limitation Treaties had excluded submarines from their calculations, giving Japan the scope to develop a critical advantage in this area. In part it had done so. Technologically advanced submarines had been produced along with world-beating torpedoes, Type-93 and Type-95, which outperformed both British and American weapons in terms of payload, speed, detection, operating distance and reliability. These advantages were undone by the failure of the Japanese Navy to develop war-winning tactics for their underwater weapons.

Stuck between defensive and offensive priorities, the Imperial Japanese Navy developed a conservative, preservation oriented command strategy that negated their submarines’ devastating offensive potential. The emphasis on the overly cautious pursuit of US warships meant that Japan’s submarines never fully exploited their potential to disrupt the long supply routes from America through the Pacific Ocean. Poor strategic thinking also undermined a building program, which was too scattergun in its approach, producing technologically innovative designs without consideration of the advantages of mass production of a few types of submarine. One can only imagine how the Pacific War might have been different if Japan, instead of wasting vast resources on the outdated battleship behemoths, Musashi and Yamato, had concentrated resources instead on the mass production of long distance submarines designed to sink US commercial ships.

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