Japanese air operations over New Guinea during the Second World War

Author: Hiroyuki Shindo

{1} From February 1942 until July 1944, a war of attrition was fought by the air forces of the United States, Australia and Japan in Papua, New Guinea, the Bismarck Archipelago and the Solomon Islands. Although this period comprises more than half the length of the war in the Pacific, somehow more attention seems to be paid in popular histories to other aspects of that war, such as the actions of the carrier fleets of Japan and the United States. The air campaign in the South Pacific, however, was of extreme importance, not just to the persons of all sides who fought there, but to the outcome of the war. This is because it was in, over and around the island of New Guinea that the Japanese Army and Navy, and their air forces, were first stopped, worn down and finally pushed back. Since it is obviously impossible to look at every aspect of that campaign in a single article, the following discussion concentrates on the major strategic and operational issues on the Japanese side. It also focuses on Japanese air operations over the main island of New Guinea, even though in actuality these operations, when seen from the Japanese side, were closely intertwined with activities undertaken in the Solomon Islands.

{2} Broadly speaking, the Japanese air campaign over New Guinea may be divided into four phases. The first phase was the Japanese Navy's offensive campaign against Port Moresby, from the spring through fall of 1942. Next, from early 1943 until about June of that year, the Japanese Army filled in for the Navy (whose air forces were increasingly committed to the Solomons campaign) and fought a campaign which was intended to be offensive but became increasingly defensive in nature. The third phase was a short period in the summer of 1943 in which the Japanese Army assigned a more positive role to its air forces in New Guinea, only to see the bulk of that force destroyed in a single air attack. Finally, the Japanese Army air forces fought an unglamorous defensive campaign for approximately a year, from the summer of 1943, before the Japanese Army was pushed out of New Guinea and the war itself shifted to the Marianas and the Philippines.

Occupation of Rabaul and the start of air operations against Port Moresby

{3} When the Japanese Army and Navy developed plans for a forthcoming war with the United States and Great Britain in 1941, the islands of the Bismarck Archipelago, particularly New Britain, were included in their target list from early on. This was because Japanese planners (especially those in the Navy) saw Rabaul on New Britain, with its excellent natural harbour, as a potential threat to Truk Island in the Carolines. Situated only 1100 kilometres from Rabaul, Truk was the site of the Japanese Navy's most important base in the central Pacific Ocean. The seizure of New Britain was therefore necessary to protect the base at Truk, and the surrounding islands had to be controlled as well, in order to secure Rabaul. While the main efforts of the Army and Navy would be aimed at the southwest Pacific area - i.e. the Philippines, Malaya, Singapore, Netherlands East Indies and other surrounding areas that made up the so-called "Southern Resources Area" - both the Army and Navy therefore assigned units to operations in the South Pacific.

{4} In the plans which received imperial sanction on 5 November 1941, the Army's South Seas Detachment was assigned the task of seizing first Guam, then airfields in the Bismarck Islands, in order to eliminate the threat posed by the enemy. Since the operation in the South Pacific was seen as the Navy's responsibility, however, the Navy's Special Landing Forces were to take over the occupation of Guam at an appropriate time, after which they would cooperate with the Army in occupying Rabaul. It was further specified that the South Seas Detachment would be replaced by the Special Landing Forces and withdrawn to the Palau Islands as soon as possible. The Navy's Fourth Fleet, based in Truk, would be responsible for supporting both the Guam and the Rabaul-Bismarcks operations. A sea-borne assault on Rabaul was accordingly made on 22 January 1942 by the Special Landing Forces, with the support of both land-based and carrier-based aircraft, and the town quickly captured.

{5} While these operations were being carried out, the Japanese Army and Navy, faced with the unexpectedly rapid success of their operations in the Philippines, Malaya and Netherlands East Indies, had to decide upon their next steps. Briefly speaking, Japan's options included continuing westward into India; invading the Australian mainland; invading New Guinea, the Solomons, Fiji and Samoa, in order to cut off Australia from the United States; and driving eastward towards Hawaii. The Navy High Command wanted to invade Australia, in order to eliminate it as potential springboard for a counter-offensive by the Allies, but the Army balked at this because it would require an excessive commitment of manpower. The Navy therefore settled for the lesser option. The Fourth Fleet, with the XI Air Fleet (the Navy's land-based air force in the Pacific theatre), was ordered to assault Lae, Salamaua in New Guinea, Port Moresby in Papua, and the Solomon Islands.

{6} In compliance with this strategy, Zero fighters of the Chitose Air Corps moved to Rabaul on 31 January. Shortly afterwards, on 2 and 5 February, Kawanishi Type 97 "Mavis" flying boats of the Yokohama Air Corps bombed Port Moresby for the first time, and the air war over New Guinea was underway. On 9 February, Gasmata (on New Britain's southern coast) was occupied, and work begun on an airstrip. To carry out further operations, the 4th Air Corps was newly created, with a nominal strength of 27 fighters and 27 bombers. It was placed under the command of the 25th Air Flotilla, and its headquarters was located in Rabaul. On 24 February, aircraft from the 4th Air Corps began bombing Port Moresby.

{7} On 7 March 1942, the Japanese High Command decided upon the operations which would follow the so-called "First Stage Operations," which had been aimed at the occupation of the Netherlands East Indies and other areas of the Southern Resources Area. The second stage of operations which was thus adopted called for the continuation of major offensive operations in order to secure a long-term, unbeatable politico-strategic situation, after which additional active measures would be taken aimed at forcing Great Britain to capitulate and making the United States lose the will to fight.¹ As part of this new strategy, the decision was made to continue the advance in the Solomons and New Guinea area, with the aim of eventually cutting off the supply route between the United States and Australia. The 7 March decision therefore confirmed what was already being executed. Lae and Salamaua on the northeastern New Guinea coast were occupied on 8 March. Two days later, the Tainan Air Corps (one of the fighter units deployed to Rabaul as part of the new strategy) sent eleven of its Zero fighters to Lae, which became an exceedingly busy advanced airbase.²

{8} Until the end of July 1942, the naval air units based at Rabaul and Lae became intensely involved in flying missions over the Owen Stanley Range to attack Port Moresby, or other Allied bases on the New Guinea mainland. Such operations consisted of either bombing missions with fighter escort, or sweeps by fighters alone. The Japanese fighter units at this time were also kept extremely busy intercepting Allied air attacks on the Japanese bases. This phase of the air war was characterized by the lack of clear superiority by either side. Although the Australians and Americans often lost more aircraft in individual air battles, Allied air strength did not diminish significantly. On the other hand, the Japanese, although suffering fewer losses, saw a slow decline in the quality of their forces as highly-trained and experienced pilots were lost and replaced by less and less experienced ones. This period was, therefore, somewhat of a stalemate, as the Japanese could not batter the Allied air forces enough to drive them out of New Guinea.

The commitment of Army air forces to the South Pacific

{9} The next stage in Japanese air operations over New Guinea involved the deployment of Japanese Army air forces in the region. After the Americans landed on Guadalcanal Island in the Solomons on 7 August 1942, the Japanese air forces based in Rabaul became involved in a two-front operation. Now they were forced to make increasingly greater efforts in the Solomons, while continuing their campaign against New Guinea (which still principally meant Port Moresby). The air battle in the Solomons would be fought principally by naval aircraft, and, as this commitment grew, the Army's air forces would play a greater role over New Guinea.

{10} The American counter-attack at Guadalcanal came as a complete surprise to the Japanese. In their estimate of the world strategic situation in March 1942, the Japanese High Command had concluded that the Americans would not mount a major counter-attack before 1943. On 12 August the Army and Navy High Commands agreed that the American landing on Guadalcanal was only a local tactical move, and the island could be easily recaptured. This view began to change after the Battle of the Tenaru River on 21 August, when the Japanese Army's Ichiki Detachment, numbering some 900 men, made the first attempt to retake Henderson Field and was almost completely wiped out. The Japanese Navy High Command now realized that it would take more than a simple operation to retake Guadalcanal, and that controlling the air around the island was a prerequisite for success. The Navy felt, however, that it alone was unable to make the necessary commitment in terms of air forces, due to the depletion of its air units in Rabaul. In late August it therefore asked the Army to send some of its forces to reinforce the air effort in the Solomons and New Guinea area.³

{11} The Army considered the Navy's request, and almost immediately rejected it. First of all, the Army was not inclined to make a major commitment in the South Pacific area, because it still felt that its traditional area of responsibility was the Asian mainland, while the Pacific Ocean area was the traditional responsibility of the Navy. This had been the understanding since the establishment of the Japanese Army and Navy in the late 19th Century, and while there was no formal written agreement to this effect, the Army and Navy's doctrines, training, tactics, strategy and equipment were all based upon it. Over the years the Army's air units had been prepared almost solely for fighting a war with Japan's traditional enemy on the continent, Russia. The Army had never even considered the possibility of conducting air operations in the New Guinea-Solomons area, and recognized that it knew almost nothing about the geographic, climatic and other conditions of the South Pacific. Not only was the Army extremely reluctant to commit its air forces in such circumstances, but it suspected that the Navy actually did have additional air forces in quieter areas of the Pacific which it could commit to the South Pacific.

{12} The Army formally replied to the Navy in late August. Besides the reasons given above, the Army explained that its air forces were spread out all over Manchuria, China, Burma and Sumatra, and in addition had to defend the Japanese homeland from possible threats from the North Pacific area. There were, it claimed, no personnel or aircraft that could be spared for the South Pacific. The Army also pointed out that its air forces had been trained and prepared for mainland operations, and were ill-suited for conducting operations or deployments over large expanses of water, which would be the case if they were committed to this new theatre. Furthermore, it was mentioned that there were no overland air routes to the South Pacific front which Army air units might follow, and that airfields and other necessary facilities were too unprepared there for them to operate properly. Thus, no agreement was reached at this stage concerning the deployment of Army air forces to the South Pacific.

{13} In mid-September a further attempt to retake Henderson Field which the Army mounted, using the Kawaguchi Detachment, also failed. As preparations commenced for yet another attempt involving the 2nd Division, the need for regaining command of the air around the Solomons was keenly recognized by Army planners. Gradually, opinion within the Army High Command began tilting towards the deployment of Army air forces to the region. In late October a proposal was produced by the Operations Section of the Army General Staff for the assignment of two fighter and two light bomber sentais (air groups) to support Army operations in New Guinea. This, however, was only intended as a temporary measure to help out the Navy while its air units were committed to the Guadalcanal campaign. (In fact, by then the Navy's major bombing missions against Port Moresby from Rabaul had all but ceased, except for night raids by one or a few planes at a time, as more and more Navy planes were sucked into the Guadalcanal campaign.) As soon as Port Moresby was captured, it was intended that the Army air forces would be pulled out again.

{14} The issue was settled shortly afterwards. From 28 October, Takushiro Hattori of the Operations Section, Army General Staff, visited the New Guinea-Solomons front, including XVII Army headquarters on Guadalcanal. His report dated 11 November called for, among other things, the deployment of army air forces to the region in order to regain air superiority. In mid-November, the Army and Navy High Commands and the Government produced an estimate of future American air power which projected that the Americans would have in the South Pacific some 11,000 army and navy first-line planes by December 1942, and 24,500 by December 1943. It was recognized that the most urgent need facing Japan was to increase her air power.

{15} Faced with looming defeat on Guadalcanal, and with setbacks in their drive on Port Moresby where Japanese forces had begun withdrawing from Kokoda on 26 October, the Army finally decided to commit some of its air forces to the South Pacific. On 18 November an "Army-Navy Central Agreement on Operations in the South Pacific Area" was signed, and the 6th Air Division was committed to the New Guinea front. This, it should be noted, was only a temporary arrangement to support the Navy's operations - that is, the Army units would be "loaned" until the Navy's air forces recovered or certain victorious conditions (such as the occupation of Port Moresby) were attained. In accordance with the agreement, sixty Nakajima Type 1 "Oscar" fighters of the 11th Sentai reached Rabaul via Truk on 18 December, and almost immediately became involved in air defence operations. By the end of the month they were flying missions against targets on mainland New Guinea, such as Buna, some of these as joint missions with Navy aircraft. On 29 December, heavy bomber units of the Army were ordered to deploy from Burma to New Guinea.

{16} Six weeks later, on 3 January 1943, another Army-Navy Central Agreement was signed which designated the areas of responsibility of the Army and Navy's air units. The Army air forces were given the mission of supporting the ground forces on New Guinea and providing their air defence, and supporting the transport of supplies to New Guinea. The Navy air forces would be responsible for air operations in the Solomons, and for air operations in New Guinea other than those assigned to the Army.⁴

{17} While the decision to withdraw from Guadalcanal was made at the end of 1942, on 4 January the Army and Navy High Commands ordered that operations on New Guinea were to be continued. The purpose of Japan's operations in the South Pacific was to be to "secure a position of superiority". Lae, Salamaua, Wewak and Madang on New Guinea were to be strengthened or occupied, and the area north of the Owen Stanleys was to be secured so that it could function as a base for operations aimed at Port Moresby.⁵ The Japanese then had 164 Army and 190 Navy aircraft on their bases at Rabaul and the surrounding area. At this stage, therefore, the Japanese had decided to abandon the southern Solomons but still intended to continue offensive operations in New Guinea, aimed at the eventual capture of Port Moresby.

{18} Thereafter, Japanese air operations over New Guinea were conducted principally by the Army, operating out of Wewak and other bases. In addition to bombing raids on Allied airbases, the Japanese air forces also had to take on ground support missions (although never conducted as closely as was the case with the Allied air and ground forces), combat air patrol over their own airbases and escort missions of ship transports operating around New Guinea. As was the case with the Japanese Navy aircraft operating against Port Moresby in mid-1942, however, the Japanese never really gained the initiative in the air, and instead were gradually pressed into the defensive.

{19} The Japanese were acutely aware of the gradually growing strength of the Americans during this period. At the end of January 1943, the Japanese Army estimated that American strength in the New Guinea area was 300 aircraft - the same as the combined strength of the Japanese Army and Navy. They estimated, however, that the Americans were producing 4,000 aircraft per month, of which the South Pacific would receive 480 (and the New Guinea front at least 80) aircraft per month. Judging that the Americans would suffer losses of 50 per cent per month, the Japanese Army projected that the Americans would have 700 aircraft in the New Guinea area by June, and 950 by September. Compared to this, the combined strength of the Japanese Army and Navy in the New Guinea-Solomons area was projected to grow to possibly 350 in June, but was not expected to exceed that number at any time.⁶ The Japanese were therefore clearly aware that if the current situation continued, the Americans would gradually attain a sheer superiority in numbers through 1943.

{20} After the Japanese successfully withdrew from Guadalcanal in early February 1943, the next major setback which befell them was the Battle of the Bismarck Sea on 2-3 March that year. In this action, an entire convoy of transports carrying the 51st Division and a large amount of heavy weapons and supplies earmarked for the reinforcement of Lae, was sunk in the Dampier Straits, along with four out of eight escorting destroyers. As a result of this disastrous defeat, which occurred even though the Japanese had provided the convoy with what they believed was an adequate fighter escort, the Japanese were forced to realize that they could no longer run major convoys of transports in areas where the Americans were able to operate their bombers more or less freely. This posed obvious problems for the supply of the Japanese troops on New Guinea.

{21} Following the Bismarck Sea battle, the Army reconsidered its entire New Guinea strategy, including the possibility of abandoning New Guinea outright and withdrawing to a new defensive line. This option was not adopted, however, because the Navy's operations - not only in the New Guinea area but also throughout the South Pacific - would be constricted by such a pullback by the Army. In addition, no new defensive line to which the Army might safely fall back was prepared, and in any case, such a retreat would only expose the Philippines, Celebes and other Japanese-held islands in the South Pacific to air attack. Joint Army-Navy studies which were held on 14 March confirmed this policy, and the Army continued to try to hold its current positions in New Guinea.⁷

Further commitment and destruction of Army air forces

{22} The lopsided defeat in the Bismarck Sea was an enormous shock to the Army High Command, which was forced to recognize even more the importance of the New Guinea front to Japan's war efforts, and that the situation there was extremely critical. As a result, the Army had to rethink its strategy for the Pacific War, and decided to make a further substantial commitment to the area, in both ground and air forces. On 25 March 1943, a revised Army-Navy Central Agreement was concluded between the Army and Navy High Commands.⁸ Regarding the South Pacific, it was agreed that the main weight of operations would be placed on the New Guinea front, i.e. the defence of Lae and Salamaua and the strengthening of bases along the northern coast, while a holding or delaying operation would be fought in the Solomons. The assault on Port Moresby, while officially still a long-term objective, was for all practical purposes abandoned, although lip service was still paid to it to avoid damaging the morale of the troops fighting in New Guinea.

{23} Reflecting this revised strategy, the Army decided to strengthen its air forces in the New Guinea area. Earlier, on 18 March, the Army High Command had decided to strengthen its air forces in the South Pacific generally, starting with the replacement of the fighter units in the 6th Air Division. The newly assigned units were the 68th and 78th Sentais of the 14th Air Brigade, which flew the Kawasaki Type 3 "Tony" fighter. These units started arriving in Rabaul in late April, and were duly deployed to New Guinea. On 2 April the Army further decided to dispatch to the New Guinea front, among other units, the 13th Sentai (flying the Kawasaki Type 2 "Toryu" twin-engine fighter) and the 24th Sentai (flying the venerable "Oscar"). These units began arriving in Rabaul in the latter half of May.

{24} The situation changed further when the Japanese discovered that the Allies were constructing airfields in the New Guinea highlands, at Mount Hagen and Bena Bena, which would threaten the Japanese airfields at Madang and Wewak. Ground operations to meet these new threats were immediately planned. As a further measure it was decided to send to New Guinea the 7th Air Division, which was a relatively new formation, having been formed in late January 1943. It had been previously assigned to bases in eastern Java, Timor and other islands in the East Indies, and, along with the defence of this area, had been scheduled to carry out air raids on the Port Darwin area. In order to meet the extremely pressing situation in New Guinea, however, it was ordered to deploy to Wewak on 19 June.

{25} Thus, the Japanese Army was busily deploying new air units to the New Guinea front in the spring and summer of 1943. While the actual movement of these forces was delayed due to the insufficient readiness of bases in the New Guinea, among other reasons, Army air strength - at least on paper - was steadily reinforced during this period. The Army made another organizational change during this period, when it created the Fourth Air Army to exercise overall command over the 6th and 7th Air Divisions. The new air army was formed in mid-June, and its headquarters began deploying to Rabaul from 25 July through 10 August.

{26} These moves were important because they indicated a shift in the Army's stance concerning its air forces in the New Guinea area. Until then, the Army had considered its air forces in the South Pacific as a temporary measure, a backstop for the Navy's efforts in the region. Over the spring and summer of 1943, however, the Army came to recognize fully that the defence of northern New Guinea against the Allied advance was its responsibility, and began to deploy additional air forces from Manchuria and elsewhere to the New Guinea front. Eventually about a quarter of the Army's air forces would be committed to the South Pacific. Considering that most of these units were the best that the Army had, and would be subjected to losses of approximately 50 per cent per month, this was indeed a major commitment by the Army.⁹

{27} As mentioned above, the 7th Air Division was ordered to deploy to New Guinea on 19 June 1943. The major 7th Air Division units which were transferred at this time were the 59th Sentai (fighters), 5th Sentai, 7th Sentai (heavy bombers) and 61st Sentai (heavy bombers). While the Eighth Area Army, which commanded the Army ground and air forces in the Solomons-New Guinea region, wanted the move to occur as soon as possible, the 7th Air Division resisted, citing the lack of readiness of the airfields to which they would deploy. Ultimately, it was not until mid-July that the fighter units were transferred, with the bomber and other units following in late July and beyond.¹⁰ Meanwhile, on 9 July, the 6th Air Division also moved its headquarters to Wewak.

{28} With these new deployments, it seemed that the Army air forces had overcome the growing disparity between the Japanese and the Allied air forces. However, in mid-June, the Army finally had to face reality, and the Operations Section of its High Command agreed upon an "Outline for Operations Guidance in the New Guinea Area" with the Operations Sections of the Navy High Command, which called for a holding strategy in New Guinea.¹¹ While this meant that the assault on Port Moresby was finally and formally shelved, the Army air forces in New Guinea still had the task of neutralizing the Allied air bases at Mount Hagen, Bena Bena, Wau, Salamaua and other places. In addition, they had to defend their own airbases, and provide fighter escort for convoys attempting to supply the Japanese garrisons on New Guinea.

{29} Defensive tasks sapped much of the Japanese Army's air strength on New Guinea. In fact, by this time the Army air forces were fighting a largely defensive campaign. Out of 1,308 sorties flown in July 1943, 494 were convoy escort, 84 were intercept and 190 were ground support. Such missions meant that fewer aircraft and pilots were available for mounting air attacks on Allied airbases, even though the need for such air attacks was well-recognized as necessary for regaining air superiority.¹²

{30} In early August 1943, the Fourth Air Army had an operational strength of 130 aircraft (the Navy's operational strength in the Solomons-New Guinea area at this time was approximately 220 aircraft).¹³ This was just one-third of what the Fourth Air Army was supposed to have on paper, and was also only an operational rate of approximately 50 per cent. The major causes of this low operational rate were widespread illness among the aircrews, along with, of course, the lack of aircraft replacements.

{31} Nevertheless, the Japanese attempted to carry out their plan to regain air superiority. On 12 August, the Fourth Air Army began to carry out air raids on the Allied airbases at Hagen, Bena Bena, Wau, Salamaua and elsewhere. This effort came to naught, however, when on 17 August 1943 Allied air armadas mounted a surprise air attack on Wewak, which was the Japanese Army's principal airbase on New Guinea. As a result of this action, over 100 Japanese aircraft were destroyed, and the Fourth Air Army was reduced to an operational strength of just over 30 planes. The destruction of the Japanese air forces meant that the Allies could now conduct air operations more or less freely as far northwest as Aitape, whereas until then they had been held to Madang.¹⁴

{32} The Army took this defeat quite seriously, since it meant a virtual end to air operations in New Guinea for the time being. The major cause for the scale of the defeat, as stressed by Eighth Area Army, was said to be the unpreparedness of the Japanese airbases. In particular, it was pointed out that the lack of sufficient aircraft shelters had left the Japanese planes vulnerable. In addition, the lack of a sufficient warning system was also identified as a culprit. The Japanese were still relying almost completely on a visual warning system, which did not provide enough time for aircraft on the ground to either scramble or be hidden. This problem was made worse by, again, the primitive condition of the airfields, which did not allow the quick scrambling of a large number of aircraft.

{33} Yet another major cause stressed by the Fourth Air Army was the fact that all of its planes had been based on Wewak and other airbases which were, quite literally, in the front line. The Fourth Air Army, along with the 6th and 7th Air Divisions, had wanted to deploy its units more in depth, with a certain number of aircraft based at airfields further to the rear. However, both the Army High Command and the Eighth Area Army had insisted that as many aircraft as possible be based at airfields at the front, to make them easier to use in operations. While this was to a certain extent inevitable, since the Japanese did not have the necessary number of airbases in the rear, it also meant that the bulk of their aircraft would be based in locations extremely vulnerable to large-scale enemy air attacks.

The end of the Japanese air forces in New Guinea

{34} After the debacle at Wewak, the Army tried to replenish its losses. At the same time, it began to strengthen its airbase at Hollandia, in order to provide more depth to the Wewak position. The Allies, however, would not wait while these efforts were being made. In September, the Allies pushed the Japanese back from their positions at Lae and Salamaua, and on 22 September they landed near Finschhafen, on the northeastern coast of New Guinea. Despite their desperate defensive efforts, therefore, the Japanese continued to slowly be pushed back in New Guinea, and in the Solomons as well. In late September, the Army air forces had at their disposal only 60 or 70 operational aircraft with which to oppose the Americans in New Guinea, even though they had two air divisions, the 6th and 7th, in the area.¹⁵

{35} Faced with these developments, the Japanese High Command was finally forced to make a major strategic change. On 15 September 1943 the concept of the Absolute National Defence Zone was adopted as policy, finally revising the strategy of 7 March 1942, mentioned above, which had called for the continuation of major offensive operations in order to secure a undefeatable strategic situation. Under the Absolute National Defence Zone concept, a delaying action would be continued in the South Pacific while a new line of defence was prepared along the Marianas-Carolines-Philippines arc. Here it was hoped that the Americans would be smashed when they tried to assault it. Counter-offensives would follow, and, if the situation permitted, offensive operations in New Guinea would be resumed in mid-1944 or later.¹⁶

{36} The Army and Navy High Commands adopted new strategies based upon the new concept on 30 September. Regarding the New Guinea area, the Second Area Army was transferred from Manchuria on 29 October and placed in charge of defending the East Indies and the western half of New Guinea up to 140 degrees east longitude. On 30 October, the 7th Air Division was transferred from the Eighth Area Army to the Second Area Army, and its headquarters pulled back to Ambon Island on 21 November.

{37} During this time the 6th Air Division, using what few planes it had (since the Japanese air forces had not recovered from the August air raid), continued its mostly-defensive operations out of Wewak. When the Allies landed at Saidor on 2 January 1944, thereby sealing off the Dampier Straits, the Fourth Air Army launched an all-out counter-attack against the invasion areas. By this time, however, it had less than 100 operational aircraft, and was able to fly only 160 sorties in all on five separate missions. Not only did this have a negligible effect on the Allied landing force, but by the time this effort was over, the Fourth Air Army was down to less than 50 operational planes.¹⁷ The Japanese Navy also launched attacks against the Saidor invasion force, since the loss of the Dampier Straits would mean that Rabaul and New Guinea would be cut off from each other. Even when the Navy aircraft operating out of Rabaul were included, however, the Japanese were down to approximately 100 operational planes for the entire New Guinea-Solomons area by mid-January, which made even a holding operation extremely difficult and indicates the desperate situation of the Japanese air forces in this entire area at this time.

{38} In order to improve its position, the Army High Command decided at the end of January 1944 to move the Fourth Air Army's centre of operations further westward than Hollandia, in order to give its positions more depth and enable it to conduct a more flexible holding operation. These orders were held up by Eighth Area Army, however, because it felt that the necessary airbases in the rear, to the west, were not ready. The High Command also decided at this time to temporarily reinforce the Fourth Air Army with some of the Second Area Army's air units. While they would remain under Second Area Army control, these units were to "cooperate" with the Eighth Area Army. The units to be loaned in this fashion were the 33rd and 77th Sentai (fighters), 45th and 75th Sentai (light bombers) and the 60th Sentai (heavy bombers). These had been slated as Second Area Army reserve, to be based in the East Indies, but were thus committed to the front line.

{39} In the meantime, the Japanese Navy's air force was finally knocked out of New Guinea and the Solomons as well. On 17 February 1944, U.S. Navy carriers launched a massive raid on the key Japanese base in the Central Pacific, Truk Island, destroying over 200 Japanese aircraft and inflicting heavy damage. The Japanese Navy had tried to hold out at Rabaul because its loss would threaten Truk, but since Truk was now directly threatened, the Japanese Navy had to replace its air losses with the only air forces available, which were those at Rabaul. Three days after the attack, all of the remaining naval aircraft of the Japanese II Air Fleet at Rabaul were flown to Truk, and the Japanese naval air arm's presence in the New Guinea-Solomons area came to an end.¹⁸

{40} On 25 March 1944, the Fourth Air Army was transferred to the Second Area Army, and its headquarters arrived in Hollandia. As an airbase, however, Hollandia was still not adequately prepared. For example, facilities needed for dispersing aircraft and supplies, and for storing supplies, were still not ready. In addition, radar and other warning and intelligence networks were also only being prepared. The same situation which had plagued the Japanese at Wewak thus existed at Hollandia. Nevertheless, by the end of March the Japanese Army had managed to assemble approximately 300 aircraft at Hollandia; of these, however, only about 150 were operational.

{41} In an eerie repeat of the earlier disaster at Wewak, the bulk of Japanese aircraft at Hollandia were wiped out in an air raid carried out over two days, 30-31 March. Over 150 planes were destroyed on the ground. The commander of the 6th Air Division and the chief of staff of the Fourth Air Army, among others, were relieved, because for them this was the second time that so many Japanese aircraft had been caught by surprise on the ground. This time, the Japanese were not given any time to recover. On 22 April 1944, the Americans landed near Hollandia. The personnel of the 6th Air Division, including its remaining pilots, were forced to retreat overland to the west, arriving in Sarmi by early May, but had to leave their aircraft behind. As a result, the 6th Air Division's remaining 100 aircraft were lost. The division was never reconstructed, ultimately being disbanded in August 1944.

{42} This left the 7th Air Division, operating at this time primarily out of bases in the East Indies. But this force, too, was severely depleted. On 25 May 1944, it had an operational strength of only 87 aircraft.¹⁹ When the Americans landed on Biak Island two days later, the 7th Air Division tried to provide air support for the defenders, but since it had so few aircraft - most of which had to be used for convoy escort and air defence missions - it was unable to do so effectively. By early July the Biak garrison had been wiped out. This was to be the last major action in which Japanese air forces operated over New Guinea. Thereafter, the major action in the Pacific would shift to the Marianas, Palaus and then the Philippines, and what remained of the Japanese Army and Navy air forces was committed to these areas. The air war in New Guinea was effectively over, having ended in an Allied victory.

Causes and implications of the Japanese defeat

{43} There was no single, direct cause for the Japanese defeat in the air battle over New Guinea. Since this issue has been covered extremely well in many works in both English and Japanese, the causes will be enumerated only briefly here.²⁰ First of all, the numerical advantage of the Allies was undoubtedly a major factor. While this was not a decisive advantage until the latter half of 1943, its effect was ultimately crucial. The Allies' aircraft strength grew steadily, while the Japanese air forces in the area barely grew, and instead often steadily decreased, in number. This applied to aircrews and ground support staff. The Allies, and especially the Americans, were able to send increasing numbers of such personnel to the front, and as the war progressed they were better trained too. In comparison, the Japanese were hard-pressed to replace their pilots and ground staff, and the flying and combat abilities of what replacement pilots were sent to the front gradually decreased in quality.

{44} The technical quality of the aircraft used was also a factor. While Japanese aircraft in this period, especially those of the Navy, were quite adequate (and in some respects excellent) for certain purposes, they were not as suited for an aerial war of attrition when compared to the Allies' aircraft. For example, Japanese machines, lacking good self-sealing fuel tanks and pilot armour, were more susceptible to damage. In addition, Japanese types were often more difficult to manufacture, which means that they were not as suited to mass production as those operated by the Allies.²¹

{45} A third factor is the generally low level of technology of Japan at this time, in comparison with the Allies. For example, as has often been pointed out, the Japanese constructed most of their airfields with manual labour. The Japanese Army recognized this as a problem as early as 1942, and had studied the issue - even establishing a base construction school in Japan²² - but little if anything had changed by 1944. This meant that the Japanese could not construct airbases quickly enough to maintain some semblance of parity with the Allies.

{46} Another technological area in which Japan was deficient, and which is sometimes overlooked, is aircraft engine technology. To the end of the war, the Japanese were unable to produce a reliable 1,500-2,000-horsepower engine which would also be small enough to be used on fighter aircraft. Because of this, they were unable to equip their fighters with pilot armour, heavier armaments and better self-sealing fuel tanks. It is often said that the Japanese sacrificed these things because they wanted to lighten their aircraft and improve their offensive capabilities. While this is true, it is also the case that the Japanese wanted to install these items, especially later in the war, but could not do so because their additional weight would worsen aircraft performance to an unacceptable degree. The Japanese were unable to develop an engine large enough to handle the weight increase, so they had to leave such items off and make do with relatively unprotected aircraft.

{47} Individually, each of these or any of the other factors which brought defeat to the Japanese air forces may not have been decisive; combined, they proved to be fatal. Faced with such a combination of negative factors, it is doubtful whether any nation could have overcome them and attained victory.

{48} Finally, what did defeat in the South Pacific air war mean for the Japanese? The obvious implication is that it exposed the Marianas, Carolines and other central Pacific islands to Allied counter-attack, as well as the East Indies and Philippines. More importantly, it destroyed the air forces of the Japanese Navy, and to a lesser degree the Army as well, in terms of pilot quality. According to one estimate, the Japanese Navy's losses between August 1942 (the start of the Guadalcanal campaign) and February 1944 (the end of its presence at Rabaul) amounted to more than 7,000 aircraft and aircrew members.²³ This was the equivalent of several years' worth of pilots.²⁴ Because the quality of pilot training declined year by year, this meant that the ranks of experienced pilots within the Japanese Navy was severely depleted by early 1944. Since the Japanese Army committed some of its best air units to the New Guinea front, the large losses these suffered meant that the Army, too, had lost a large number of its best pilots.²⁵ It is, therefore, not much of a surprise that the Japanese air forces, especially those of the Navy, suffered such lopsided defeats in the 1944 battles in the Marianas and the Philippines.

{49} The Japanese were able, within a few months, to partially replenish the numbers of aircraft and pilots it had awaiting the Allies in 1944. What they could not replace were the qualitative losses they suffered in the South Pacific. Notwithstanding that Japanese aircraft were becoming outmoded by 1943, right up to the war's end these could be very effective in the hands of a good pilot. But when the quality of the pilots declined, the result was disastrous. Without an effective air force, the Japanese would have had an exceedingly difficult time holding off the Americans in 1944, especially since the Americans' air forces had steadily improved, both in quality and quantity, during 1943 and early 1944. The greatest implication of the Japanese defeat in the South Pacific therefore may be that it eliminated Japan's ability to achieve air superiority anywhere in the Pacific during the remainder of the war.

© Hiroyuki Shindo

The author

Hiroyuki Shindo is currently an assistant professor in the Military History Department of the National Institute for Defense Studies, Tokyo. His special areas of interest are US-Japan diplomatic and military relations in the 1930s and 1940s, and the military history of the Second World War.

Notes

¹ Takushiro Hattori, Daitoa Senso Zenshi (A Complete History of the Great East Asia War) (Tokyo: Hara Shobo, 1965), p.294.

² The activities of the Navy's air forces based in Rabaul and Lae during the spring and summer of 1942 have been excellently depicted in Saburo Sakai, Sakai Saburo Kusen Kiroku (Sakai Saburo Air Combat Records)(Tokyo: Shuppan-Kyodosha, 1953) (English translation: Samurai! (Dutton, 1957)) and many other works.

³ For a detailed account of the process by which the Army air forces were committed to the South Pacific, see Boeicho Boeikenkyusho, ed., Senshi Sosho Tobu Nyu-Ginia Homen Rikugun Koku Sakusen (Army Air Force Operations, Eastern New Guinea) (Tokyo: Asagumo Shinbunsha, 1967), pp.20-63.

⁴ Boeicho Boeikenkyusho, ed., Senshi Sosho Rikugun Koku no Gunbi to Unyo (3) Daitoa Senso Shusen made (Equipment and Operation of Army Air Forces (3) Until the end of the Great East Asia War) (Tokyo: Asagumo Shinbunsha, 1976), p.72.

⁵ Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Tobu Nyu-Ginia Homen Rikugun Koku Sakusen, p.155.

⁶ Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Rikugun Koku no Gunbi to Unyo (3) Daitoa Senso Shusen made, p.75.

⁷ Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Tobu Nyu-Ginia Homen Rikugun Koku Sakusen, pp.185-90.

⁸ Takushiro Hattori, op. cit., pp.405-407.

⁹ Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Rikugun Koku no Gunbi to Unyo (3) Daitoa Senso Shusen made, p.95.

¹⁰ Among other reasons, the slowness with which the Army transferred its air forces around the Pacific has been given as one of the reasons why the Army air forces were relatively ineffective against the Allies, because that prevented them from deploying and operating rapidly in areas where they were most needed. Masatake Okumiya, Rabaul Kaigun Kokutai (Rabaul Naval Air Corps) (Tokyo: Asahi Sonorama, 1998), pp.169-170.

¹¹ Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Rikugun Koku no Gunbi to Unyo (3) Daitoa Senso Shusen made, pp.93-95.

¹² Ibid., p.104.

¹³ Ibid., p.101.

¹⁴ Ibid., pp.107-108.

¹⁵ Takushiro Hattori, op. cit., p.504.

¹⁶ Takushiro Hattori, op. cit., p.498.

¹⁷ Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Rikugun Koku no Gunbi to Unyo (3) Daitoa Senso Shusen made, p.152.

¹⁸ Okumiya, op. cit., pp.366-369.

¹⁹ Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Rikugun Koku no Gunbi to Unyo (3) Daitoa Senso Shusen made, p.187.

²⁰ For example, see Eric Bergerud, Fire in the Sky (2000), for an excellent, interesting and in-depth analysis of the air war in the South Pacific.

²¹ For an analysis of Japan's aircraft technology and its effects on the war as seen from the Japanese side, see for example Kunio Yanagida, Reisen Moyu (Zero Fighter Aflame) (Tokyo: Bungei Shunjyu, 1984-1990).

²² Boeicho Boeikenkyusho, ed., op. cit. Senshi Sosho Rikugun Koku no Gunbi to Unyo (3) Daitoa Senso Shusen made, p.135.

²³ Bergerud, op. cit., pp.667-668.

²⁴ An exact equivalent is difficult to calculate, because the Japanese were expanding their pilot training programs every year even before the Pacific war began.

²⁵ According to one estimate, nearly 800 aircraft were lost by the Japanese Army in the South Pacific. Bergerud, op. cit., p.668.