Nachi under attack from carrier aircraft from US Navy Task Group 38.3 in Manila Bay on November 5, 1944. The ship was photographed by aircraft from the US carrier Essex. At this point in the attack, it remains undamaged. (Naval History and Heritage Command)
The ultimate cause of the IJN’s demise in the Pacific War was directly linked to two things. The first should have been easily foreseen by the Navy’s leaders. When the Japanese initiated a war against the United States, they did not fully appreciate the nature of their opponent. While the Japanese knew the United States possessed many times the industrial potential of Japan, they failed to draw the appropriate conclusions. During the war, the USN commissioned 18 fleet, 9 light, 77 escort carriers, eight battleships, 13 heavy and 33 light cruisers, 349 destroyers, 420 destroyer escorts, 203 submarines, and a wealth of supporting amphibious and auxiliary ships. Against these overwhelming numbers, crewed by men able to adapt to the fast-changing pace of wartime technology, there was probably little the IJN could do to avoid defeat. However, by adhering to outdated and ill-suited strategies, the Japanese hastened their own demise.
The second factor crippling the IJN’s wartime operations was its belief in the decisive battle concept which went unchallenged throughout the war. The first attempt to fight a decisive battle at Midway was defeated by extremely sloppy staff work at all levels and an American determination not to operate according to the Japanese script. Ironically, the closest the Japanese ever got to a decisive battle against the USN was the six-month death-struggle for Guadalcanal. This escalating battle for an insignificant island on the fringe of the Japanese perimeter did not meet the Japanese definition of decisive, so the opportunity went unrecognized. Accordingly, they never invested the resources required to defeat the USN while the two navies were still at rough numerical parity. Biding its strength until 1944, the IJN made two final attempts to conduct a decisive battle, and each ended in disaster.
Modern war between industrialized nations is decided not by a single battle, but by logistics, good intelligence, solid planning, technological innovation and adaptation, and industrial output – all the things the IJN gave short shrift to or did poorly. The Japanese were well aware that they could not compete with the Americans in these areas, so they planned to make up the difference with superior fighting spirit and determination. This was another indication that they simply did not understand the nature of modern war.
As flawed as Japanese naval strategy was, their tactics were often superior, at least in the initial stages of the war. The IJN trained intensively for war during peacetime under conditions as close to combat as could be devised. Though the decisive battle concept was a total bust, many of the tactics developed during training for the decisive battle were directly transferable for use by the IJN’s cruiser and destroyer forces. This was easily demonstrated during 1942 when the two sides were equally matched numerically and both used prewar tactics. In the Pacific War’s first large surface engagement, the Battle of the Java Sea in February 1942, an Allied naval force was shattered by Japanese cruiser-destroyer force using superior night-fighting doctrine, equipment and tactics.
The Guadalcanal campaign featured five major surface battles and two carrier actions. In the five surface actions, the Japanese were the clear winners in two, with two developing favorably for the USN and the fifth essentially ending in a draw. The results of these actions, and other smaller engagements, showed that both sides took heavy losses, but that the Japanese held an edge. In combatant ships, the USN’s losses totaled 25 ships, while the IJN lost 18. Of these, 15 Allied and eight Japanese ships were sunk in surface actions, leading to the inevitable conclusion that the IJN was simply better in surface combat. The remainder of the losses were attributable to air power, proving that the Japanese navy was already showing its inability to defend against air attack and that its strategy of fighting a major battle under conditions of air inferiority was flawed.
The losses sustained by the Japanese, though less than the USN’s, simply could not be sustained. The attrition to the IJN continued into 1943 during the fierce battles in the Central and Northern Solomons. From March–November 1943, 25 Japanese destroyers were lost in the Solomons and the Bismarck Sea, and these losses were impossible to replace. Of the seven major battles fought during1943 in the Solomons, several resulted in Japanese tactical victories, but overall the ratio of losses demonstrated that the Japanese had lost the tactical edge they held during 1942 off Guadalcanal. After this point, the growing numerical and technological (primarily evidenced by radar) superiority of the USN made Japanese tactics largely irrelevant.
Operations in 1944 featured the crippling of the IJN’s carrier force and the reliance on their still-powerful surface force to fight yet another iteration of the long-sought decisive battle. The Japanese had carefully hoarded their carrier force since late 1942 for the next opportunity for a major carrier engagement in mid-1944. With nine carriers massed together, supported by land-based air, the Japanese had reason to believe that the Battle of the Philippine Sea would be decisive. Though this was a correct prediction, it was decisive in favor of the USN, which used radar and well-trained aviators flying superior fighters to destroy the Japanese carrier raids and cripple the IJN’s carrier force for the remainder of the war.
Nothing shows the idiocy of Japanese wartime strategy more than the next attempt to fight a decisive battle when the Americans invaded Leyte in October 1944. The best that the IJN could devise was to mount an operation that would place the IJN’s surviving heavy ships into Leyte Gulf in order to attack whatever shipping remained there several days after the initial landings. It is hard to imagine that even the Japanese believed that an operation designed to sink empty or easily replaceable transports could provide a significant impact on the pace of the American advance toward Japan. Making the whole endeavor even more pointless is that if the fleet had followed its orders, it would almost certainly have been caught inside Leyte Gulf and totally destroyed. Even if it survived by some miracle and had actually gained a measure of success, there was insufficient fuel available to allow another follow-up operation for many weeks. The entire operation must be seen as reckless in the extreme and designed more as an opportunity for the ceremonial destruction of the IJN than as a serious operation designed to turn the tide of the war.
The light carrier Shoho was attacked on the morning of May 7 1942 at the Battle of Coral Sea by a total of 93 aircraft from two American carriers. Within 15 minutes, the carrier was ripped apart by some 13 bombs and at least seven torpedo hits, sinking quickly with heavy loss of life. Shoho was the first IJN carrier lost during the war. (Naval History and Heritage Command)
While the IJN searched vainly for its decisive battle, it totally disregarded the importance of protecting its own maritime trade. For an island nation dependent on moving raw materials into the home islands for survival, let alone to conduct a major war, such disregard can scarcely be believed. This weakness was concealed in 1942 by the extent of Japanese success and by the fact that problems with American torpedoes and tactics limited Japanese merchant losses to a survivable 900,000 tons. By 1944, the effect of the American submarine campaign and the introduction of American airpower into Japan’s inner defense zones brought Japanese merchant losses to unsustainable levels. Of the 6.4 million tons of merchant shipping available to the Japanese before the war, only 1.5 million tons remained at the end of the war and these were pinned down in port and therefore unable to move raw supplies to the homeland. The only reasonable explanation for this neglect was that protection of merchant shipping could not contribute directly to the decisive battle, providing another example of the IJN’s inability to comprehend the nature of modern war.
Even with this backdrop of overall defeat, there were clearly components of the IJN which fought well and earned the respect of their opponents. First among these was the IJN’s carrier force, which opened the war with such a resounding note. When the Japanese concentrated their naval airpower into a single formation in April 1941 it was truly a revolutionary step. This pioneering move made the Kido Butai supreme in the Pacific, at least briefly. Japanese carrier doctrine, with its ability to mass airpower, at both the operational and tactical levels, was clearly superior to American carrier doctrine through 1942, which continued to rely on individual carrier air groups. However, American carrier doctrine developed rapidly and by late 1943 had eclipsed the Japanese. Even at its zenith, the Kido Butai was only a raiding force. When the American carrier force reached its peak, it had the capability to exert sustained power even against heavily defended targets, something the IJN never even contemplated.
The original Kido Butai comprised a mix of carriers which possessed great striking power at the expense of staying power. While Akagi and Kaga must also be seen as successful conversions, the Soryu class, which epitomized the IJN’s desire to create a fast carrier with a large air wing at the expense of protection, proved unable to survive damage in its only clash with enemy carriers. In the Shokaku class, Japanese carrier design reached its peak. Both ships proved very tough and capable units in action and had very few foreign contemporaries.
The main problem with building ships as capable as the Shokakus was that they could not be produced in numbers during wartime. In fact, the Japanese completed only a single fleet carrier during the war in time to see action in a carrier engagement. This was the Taiho – certainly a fine design, but clearly not one that could be repeated in sufficient numbers to allow the IJN to sustain a campaign against the USN. The Unryu class was a design conceived with ease of construction in mind. However, it was actually a step back, as it possessed little protection, and by 1944 the size of its air group compared unfavorably with those of the new American fleet carriers already in service. The final fleet carrier, Shinano, was an anomaly but one that possessed considerable potential. However, by the time of its commissioning, it was irrelevant.
Japanese prewar plans for preparing merchant and auxiliary ships for conversion into carriers were also a mixed success. While the program was successful in providing 11 ships, these were generally not of a standard to be successful in fleet service. The most useful conversion was the Hiyo class. For the Japanese, these were important additions to their carrier force, as they came immediately after Midway. Generally, these ships offered the capability of the Soryu class but with a lower speed and reduced protection. Of the ships converted from merchants to act as fleet carriers during the war, they must be judged as the most successful in any navy. The five ships converted from auxiliaries into light carriers generally proved useful in service with the exception of Ryuho. However, even the more successful conversions could operate only a small number of aircraft, and, while maneuverable, were largely unprotected.
The IJN’s five escort carriers rendered little useful service aside from acting as aircraft ferries. Not surprisingly, with no catapults and insufficient speed, they were a failure in their envisioned role as fleet units. Even used in a more suitable role as convoy escorts they proved a failure. The contributions of the IJN’s five escort carriers contrast miserably with the key roles played by the over 125 escort carriers that entered service in the RN and USN.
The most unsuccessful component of the IJN was its battleship force. For all their prewar expectations, the Japanese battleship force contributed very little to Japan’s war effort. While this failure can be largely attributed to the demise of the battleship in the dawning age of airpower, Japanese battleships never found a new role for which they were well suited, unlike their American counterparts.
In the opening stages of the war, only the Kongo class was active. Despite the speed of these ships, which permitted them to operate with the carrier force, they were basically unsuited to that role, since they lacked sufficient antiaircraft power to defend themselves, much less the carriers. Most of the IJN’s battle line remained inactive during the initial stages of the war. All were committed at Midway, where they contributed nothing.
In the six-month struggle for Guadalcanal, the IJN’s battleships had the potential to make significant contributions to a Japanese victory. Against American surface forces, or used against the pivotal airfield on Guadalcanal, their firepower would have been a significant addition. The Kongo class was committed to close action around the island, but none of the heavier battleships ever got close to it. Whether this was because of a lack of proper ammunition for shore bombardment, a lack of fuel in the forward areas, or a reluctance to commit what was still viewed as the IJN’s most important assets, has not been fully explained. However, the USN did not share the same reluctance, and risked two of its most modern battleships at a key point in the battle. While Yamato sat at Truk, the battle for Guadalcanal was being decided in November 1942. Had the Japanese decided to risk their prestige battleship, the remaining American carriers and the small air force on Guadalcanal would not have possessed the killing power to handle it. By 1944, the Americans could commit literally hundreds of aircraft to pound even the most armored ships under the waves, but in 1942 this would have been problematic. In the end, the Guadalcanal campaign cost the Japanese two battleships, and the result was still a major defeat.
After Guadalcanal, the battleships were hoarded until late in 1944, when the American invasion of the Philippines forced the IJN to commit its last resources. Following Philippine Sea and the demise of the carrier force, the success of the Japanese plan to defend the Philippines was predicated on the firepower of its nine remaining battleships. Despite being committed with almost no air cover, this strategy placed the four remaining battleships of Force “A” in a favorable tactical position to inflict a sharp local defeat on the Americans. Even in this battle against unarmored, slow escort carriers and their weak escorts, the Japanese battleship force came out second with a display of poor gunnery and lack of aggression. The battle for Leyte cost another three battleships, and again resulted in a major defeat.
Leyte broke the back of the IJN and five of the remaining six battleships returned to Japan to sit idle for lack of fuel. Of the five, only one remained afloat at the end of the war. Three others had been sunk in harbor. The fate of Yamato symbolized the ineffectiveness of the entire Japanese battleship force. Built at great cost to the nation, it fired its main armament at a surface target once during the war. This was not during a great clash of battleships to decide control of the Pacific, but at an insignificant escort carrier. Unable to face the prospect of national defeat while leaving the symbol of the nation intact, the IJN recklessly committed Yamato on a virtual suicide mission in the face of waves of carrier aircraft. Its loss contributed nothing and epitomized the futility of Japan’s battleship force.
Since the Japanese were reluctant to commit their battleships, the IJN’s heavy cruiser force was forced to fill the gap. Japanese heavy cruiser designers produced a series of fast, well-armed and tough ships with considerable offensive capabilities. However, given this emphasis on offensive capabilities, Japanese heavy cruisers were not as well balanced as the later American treaty cruiser designs or those completed during the war.
The persistent issue of overweight designs resulted in several undesirable consequences. Instability was a problem that reached its zenith in the design of the Mogami class, which required a wholesale reconstruction to rectify it. Additional weight also reduced endurance and freeboard; the latter condition had the effect of pushing more of the main armor belt below the waterline, which increased the potential for damage from enemy shellfire. For all cruiser designs, underwater protection was inadequate, since the Japanese themselves had calculated that their passive torpedo defenses could only withstand 440lb of high explosive. Since the standard American air-launched torpedo during the war contained a warhead with 600lb of Torpex (50 percent more powerful than TNT), and the Mark 14 submarine-launched torpedo had a Torpex warhead with 643lb, Japanese cruisers were obviously vulnerable to torpedo damage.
The principal design difference between Japanese cruisers and American cruisers was the inclusion of a heavy torpedo armament. As predicted by some Japanese designers, inclusion of torpedoes proved to be a double-edged sword. As has been recounted, use of cruiser-fired torpedoes was decisive in several instances, namely during the battles of Java Sea and Savo Island. However, the loss of three cruisers (Mikuma, Furutaka and Suzuya) was directly attributable to detonations of onboard torpedoes, and two other cruisers (Aoba and Mogami) were severely damaged in the same way.
During the course of the war, the IJN’s cruisers proved increasingly vulnerable to air attack, although this was not in itself due to a design flaw. Indeed, the primary cause for the destruction of the majority of the IJN’s heavy cruisers (ten of 16 heavy cruisers lost) was air attack. The Japanese were not unaware of this vulnerability, but the continuing addition of growing numbers of light antiaircraft guns on the ships did nothing to lessen their vulnerability.
Nevertheless, heavy cruisers must be seen as one of the IJN’s success stories. These ships spearheaded Japanese expansion into the critical Dutch East Indies, shattering all Allied opposition. Japanese heavy cruisers served with distinction during the Guadalcanal campaign, marked by the victory at Savo Island. By the end of the war, all but two had been sunk as the Americans exploited Japanese weaknesses in antiaircraft and antisubmarine warfare, but the fighting record of the IJN’s heavy cruiser force was unmatched by the heavy cruisers of any other navy during World War II.
The IJN’s light cruisers were underarmed compared to their foreign counterparts, carried almost no or limited antiaircraft protection, and possessed a mediocre torpedo armament. This translated into a record of steady, if unglamorous service. Overall, the IJN’s 5,500-ton designs must be considered marginally successful given the undoubted success of the IJN’s destroyer forces, which the light cruisers were responsible for leading.
In addition to their role as destroyer squadron flagships, Japanese light cruisers were employed in many other roles. They enjoyed no great success in any of these, but performed all adequately. However, as the war progressed, and American air and naval power penetrated deeply into Japanese-held areas, the weaknesses of the IJN’s light cruisers became obvious. Of the 22 non-training light cruisers, only two survived; 11 were sunk by submarine attack, seven by air attack and two in surface engagements. Throughout the war they proved vulnerable to air attack. Unable to protect themselves and unable to take a great degree of damage, seven were sunk, and almost every ship damaged at least once, by air attack. Most apparent is their vulnerability to submarine attack. Since most light cruisers were not considered major fleet units, they were assigned secondary missions. In this capacity, they were not given adequate antisubmarine protection, and the results were evident. Japanese light cruisers did not possess dedicated antitorpedo defenses, so when they were torpedoed, one or two torpedoes were adequate to sink the ship.
The utility of the last generation of light cruisers, the Agano and Oyodo classes, must be questioned. The Japanese notion of using light cruisers to lead destroyers and submarines was deeply ingrained, and the design of the last light cruisers built reflected this specialized role. What resulted in the case of the Agano class was a beautiful ship, but one that was outclassed by foreign light cruiser designs in the areas of firepower and protection. The concept of using light cruisers as an operational flagship for submarine squadrons was never more than a fantasy, so this made the Oyodo nothing more than a white elephant. In the final analysis, the IJN’s light cruiser ranks were a collection of overaged, underarmed, and marginally protected ships suited only for specialized roles.
The IJN’s destroyer force went to war possessing some of the most powerful ships in the world. However, an assessment of its strengths and weaknesses reveals that these ships were suited for only a single mission: delivering torpedo attacks. Overall, Japanese destroyers were excellent torpedo boats, but were not well-balanced destroyers, since they were deficient in antiaircraft and antisubmarine warfare capabilities. In the early part of the war, with patchy Allied resistance and during the series of night battles in the Solomons against American surface ships, Japanese destroyers were well suited for the roles they were tasked to execute, and as a result performed excellently. However, as the war went on and the Americans brought increasing numbers of submarines into play and gained air superiority over the battle areas, the weaknesses of Japanese destroyers were ruthlessly exposed.
The fourth wave of attacking US aircraft, including torpedo bombers from the carrier Lexington, delivered a devastating attack on the immobile cruiser, Nachi. As many as five torpedoes hit the ship, blowing off the bow and the stern following the explosion of the aft magazine. The result of the attack is shown in this photo. Only 220 men survived the sinking and subsequent strafing by American aircraft; 807 were killed, including 74 from the embarked Fifth Fleet staff. (Naval History and Heritage Command)
| Japanese Destroyer Losses 1941–45 by Cause | ||||
| Surface | Submarine | Air | Other/Combination | Surviving |
| 26 | 39 | 49 | 13 | 39 |
By far the leading causes of losses among the 166 Pacific War IJN destroyers were submarine and air attack. Losses in surface actions were relatively minor in comparison. Other causes of losses included mining, collisions, and a single loss to shore batteries. Losses increased throughout the war, with only four being lost in 1941, 17 in 1942, 33 in 1943, an astounding 58 in 1944, and 15 in 1945.
A review of each class supports this basic assessment of the strengths and weaknesses of the Japanese destroyer force. At the start of the war, the Minekaze class was considered obsolescent by the Japanese. Most were assigned to secondary commands and undertook general patrol and escort duties. In this capacity, the Minekaze class proved to be undistinguished submarine hunters, since its ships lacked modern sensors or antisubmarine weapons. Of the 13 ships, only five survived, and of the eight lost, seven were sunk by submarines.
The Kamikaze class formed two destroyer divisions at the beginning of the war and was briefly active in the forward areas before being assigned escort duties in rear areas. Of the nine ships, seven were lost, with submarines again being the primary agent of destruction.
The 12-ship Mutsuki class saw extensive service during the war, and all 12 were lost before the end of 1944. Unlike the previous two classes of older destroyers, they were employed in the forward areas, with almost the entire class seeing duty in the Solomons campaign. Ten units were lost to air attack, clearly demonstrating the inability of these ships to deal with concerted air assault. One ship was lost in surface action and, unusually, only a single ship was sunk by submarine attack.
After their stability faults had been addressed, the 19 Group I and II Special Type destroyers rendered good service. Fubuki-class units saw extensive action in the Solomons area, but were eventually assigned secondary duties as newer destroyers entered the fleet. Only one ship, Ushio, survived the war. Of the 18 ships sunk, six were lost to submarine attack, seven to air attack, three to surface action, and two were mined. Of the four Group III Special Type ships, only one survived.
The original Hatsuharu design also possessed severe stability problems that were corrected before the war. None of the six units survived, and four of these were sunk by air attack. The similar Shiratsuyu class also saw extensive service, with none of the ten ships surviving the war. Only one ship was sunk by air, but five were destroyed by submarine attack and three sunk in surface engagements.
The most telling statistic of all regarding the IJN’s destroyer force is that, of the 48 ships that made up the Asashio and the Type A classes, comprising the most capable Japanese destroyers, only a single ship survived the war. This alone confirms the bitter nature of the combat that Japanese destroyers were forced to fight. The late-war destroyers of the Akizuki, Matsu, and Tachibana classes in many cases were not completed in time to see service beyond home waters. This explains the survival of 29 of these units.
The performance of the IJN’s submarine force fell far short of Japanese expectations during the Pacific War. Originally designed to be an adjunct in the set-piece decisive battle, they were ill-suited to play a role in the war which developed.
The IJN had 64 submarines available at the start of the war. Of these, only 41 were modern fleet boats, two were modern medium submarines, and 21 were obsolete. The lackluster performance of the Japanese submarine force began immediately when 27 fleet submarines deployed off Hawaii in 1941 with very disappointing results. In 1942, the Japanese failed to develop a coherent submarine strategy. Linked to fleet operations, it did achieve some notable successes, but Japan’s inability to supply garrisons demanded emergency measures and the submarine force was increasingly employed on supply missions.
The submarine force carried out various different missions, from attacking shipping off the US West Coast, to carrying midget submarines to targets in Australia and the Indian Ocean, and carrying out transport operations to Europe. However, most late-war operations were based on ill-coordinated responses to US attacks on Japanese-held islands. This typically featured setting up a submarine picket line against advancing US forces. Most often these lines were moved elsewhere when the deployment or timing of the original line was found to be faulty. In the face of US forces equipped with radar and superior intelligence, these tactics were suicidal. Throughout the war, the missions to supply cut-off garrisons increased, as did the losses.
Japanese submarines were generally much larger than any other navy’s boats. Even the C1 Type boats, smallest of the A1/B1/C1 types, were significantly larger than US fleet boats. This large size was required to fulfill their envisioned role as long-range, high-surface-speed torpedo platforms, but made them ill-suited to the type of antisubmarine war they were to experience. Being large, their diving time was excessive. Once detected, they were fairly easy to destroy because of their slow submerged speed, poor maneuverability, and limited diving depths. They were also noisy under water. To make things worse, Japanese boats were equipped with generally outdated radar and acoustic equipment. The increasing effectiveness of Allied antisubmarine measures was not appreciated by the Japanese until it was too late, partly because the IJN had neglected its own antisubmarine forces before the war and had no real idea what modern antisubmarine warfare had become.
The wreck of Okinami pictured in February 1945. Okinami was one of many Japanese destroyers lost during the Philippines campaign to American air attack because of insufficient air cover and inadequate antiaircraft capabilities. The ship was sunk on November 13, 1944 in Manila harbor, but only 14 crewmen were lost. (Naval History and Heritage Command)
The Japanese developed a multiplicity of designs during the war and never arrived at a standardized design adapted for mass production. During the war they added 126 submarines to their fleet, making a total of 190 used during the war. All told, 129 submarines were lost – 70 to surface forces, 19 to Allied submarines, 18 to air attack, and 22 others to unknown or various causes. In return, Japanese submarines accounted for some 185 merchant ships of just over 900,000 GRT (gross register tons) and a paltry total of warships sunk including two carriers, two cruisers, and ten smaller warships. Compared to the German U-boats’ toll of over 2,500 merchant ships alone, this was a poor harvest. All considered, the exploits of the IJN’s submarine force were among the more disappointing stories of the Pacific War.
The performance of the IJN’s individual units, particularly during the early parts of the war, displayed the Japanese notion that quality would triumph over quantity. In a short, quick war, this core Japanese belief could have been correct, as it had been against the Russians in 1905. The lesson of the war against the Russians for the IJN was that reliance on a decisive battle was a viable strategy. When the Pacific War turned from a war of sweeping Japanese advances to one of attrition, the IJN was unable to adjust. The Japanese remained fixated on the development of a decisive battle. Against a modern opponent, with the industrial strength to sustain a war of attrition, this strategy, even if supported by excellent tactics, was disastrous. Most importantly, the decisive battle concept against the United States was totally void since no one battle could defeat a major industrial nation. More than anything else, the IJN’s inability to comprehend, much less prepare for, total war led to its total and utter destruction.