Though delayed by the last-ditch resistance of General MacArthur's forces on Bataan, the ultimate conquest of the Philippines gave Japan a vital link with its newly-won empire to the south and a strategic hub for the defensive structure planned by Imperial General Headquarters to guard that empire against the anticipated Allied counter-offensive.1 Meanwhile Japan's forces in the Pacific forged another link in this long-range defensive chain by a thrust into the southeast area2 to take Rabaul and Kavieng, in the Bismarck Archipelago.
In framing its initial war plans, Imperial General Headquarters had fully assumed that the United States and Great Britain, once they had recovered from the blows dealt them in the first phase of hostilities, would launch counter-offensives against the Japanese forces in the conquered territories. The southeast area, centering around the Australian subcontinent, seemed a probable starting-point for such counter-offensive action. To strengthen the Japanese defense perimeter in this sector, therefore, the Army and Navy High Commands decided to effect the "seizure of strategic points in the Bismarck Archipelago,"under the terms of the Army-Navy Central Agreement of 10 November 1941.3
In the initial plans, Rabaul, strategically located at the northeastern tip of the island of New Britain, was fixed as the main Japanese objective. Of great potential value to the Allies as a naval base for the protection of communication lines to Australia, it could also serve as a base for bomber attacks against the key Japanese naval stronghold of Truk. Conversely, its control by Japan would secure Truk's southern flank and give the Japanese Navy an advance air base from which the sea area to the northeast of Australia could be reconnoitered for signs of Allied fleet activity.4
Under the Army-Navy Central Agreement, the invasion of the Bismarcks was jointly
assigned to the Army's South Seas Detachment and the Navy's South Seas Force (Fourth Fleet as a secondary mission to be carried out after the occupation of Guam.5 Accordingly, after Guam was successfully seized on 10 December 1941,6 the Fourth Fleet, under command of Vice Adm. Shigeyoshi Inouye, concentrated at Truk to complete invasion preparations, and on 4 January the South Seas Detachment under Maj. Gen. Tomitaro Horii was alerted at Guam.7
In view of Rabaul's obvious importance to the Allied defense of Australia, which became more precarious as the areas to the north fell under Japanese control, Imperial General Headquarters anticipated that an invasion attempt would meet with reprisal by Allied naval forces. Intelligence reports indicated that these forces in southern Australian waters consisted principally of two heavy cruisers and four light cruisers of the British Navy, reinforced by two American light cruisers. The Navy also estimated that American carrier and cruiser strength in the Hawaii area might be diverted to the Southwest Pacific.
On the other hand, it was known that Allied defense installations at Rabaul had been negligible, and enemy garrison strength weak. Assuming that the Allies had not yet had sufficient time to deploy additional forces to the area, it was estimated that the South Seas Detachment would encounter not more than 1,500 Australian ground troops and, at the maximum, ten aircraft.
In preparation for the invasion operations, Navy shore-based air forces at Truk began an air offensive against Rabaul on 4 January, using 16 medium bombers and nine flying boats in the initial strike.8 Thereafter air attacks were carried out continuously and, when the actual invasion got under way, were extended to include Salamaua, on the east coast of New Guinea.
The South Seas Detachment, composed of the 144th Infantry Regiment reinforced,9 left Guam on 14 January aboard a transport convoy escorted by units of the Fourth Fleet. In addition to the escort force, two separate surfaces forces and a submarine force of six ships covered the operation against possible enemy fleet reaction. (Plate No. 30) The first of the surface forces was a powerful task force composed of the main body of the First Air Fleet, i.e. the carriers Akagi, Kaga, Zuikaku and Shokaku (all participants in the Pearl Harbor strike), two battleships, two heavy cruisers, one light cruiser and nine destroyers, under command of Vice Adm. Chuichi Nagumo. The second was a scouting force of four heavy cruisers (6th Cruiser Division) under Rear Adm. Aritomo Goto. The submarine force was assigned to patrol the southern
approaches to the St. George Channel, separating New Britain and New Ireland.
About noon on 20 January, 86 planes from the Akagi, Kaga, Zuikaku and Shokaku delivered heavy strikes against Rabaul, followed up on 21 January by surprise raids by 75 planes of the Zuikaku and Shokaku on Lae, Salamaua, and Madang, on the east New Guinea coast. The two surface forces (minus the Akagi and Kaga, which had already been detached from the operation) then stood by north of New Britain to await possible counterattack by enemy naval forces. Meanwhile, the invasion convoy entered Rabaul Harbor on schedule at 2300 on 22 January. Beginning at midnight, a single Allied plane dropped parachute flares over the convoy anchorage for three hours consecutively, but no active interference materialized. The South Seas Detachment landed at daybreak on 23 January, encountering only weak resistance at the Vunakanau airfield, which was occupied by noon of the same day.
Simultaneously with the Rabaul landing, two companies of special naval landing force effected the bloodless occupation of Kavieng, on the northwest coast of New Ireland.10 Mopping-up operations continued on New Britain, New Ireland and adjacent islands until the end of January, and by 5 February the South Seas Detachment on New Britain had posted its troops north of a line from the Warangoi River to the Keravat River, then shifting its attention to the construction of defense installations throughout the Rabaul area. On 9 February additional naval landing force was put ashore at Surumi, on the south coast of New Britain, and the small adjacent island of Gasmata in order to strengthen the outer defenses of Rabaul.
Within a week of the initial landing, the Rabaul airstrip was operational, and on 30 January the first unit of nine Zero fighters flew in from Truk. Early in February approximately 20 medium bombers arrived at the Vunakanau airfield, 10 miles southwest of Rabaul, and by the end of the month the entire complement of the 4th Air Group of the 24th Air Flotilla-48 medium bombers, 48 fighters and 12 flying boats-was based in the Rabaul area.11
Although the seizure of advance bases in the Bismarcks represented the maximum southeastward penetration to which the Army12 and Navy High Commands felt able to commit themselves pending the outcome of the initial major operations, the staff of the Fourth Fleet, based at Truk, had strongly urged during the early planning stage that, in order to secure Rabaul, it would also be essential to occupy strategic points beyond the Bismarcks, principally Tulagi in the Solomons, and Lae-Salamaua in New Guinea.13 This recommendation did not obtain sufficiently strong backing from
Combined Fleet headquarters to win inclusion in the plan of first-phase operations, but it nevertheless was adopted as a tentative item of future Navy action conditional upon over-all war developments.14
By late January 1942 these developments, especially the crippling blows dealt to Allied fleet and air power, had increased the optimism of the High Command to such an extent that the Navy, with the virtually unopposed seizure of the Bismarcks, took the initiative in urging a further advance to bases in the Solomons and southeastern New Guinea, including not only Lae and Salamaua but Port Moresby, on the Gulf of Papua. The principal reasons advanced in support of this plan were:
Extension of the Navy's offensive plans to take in Port Moresby, only a little over 300 miles across the Torres Strait from the northeast tip of Australia, was largely in recognition of the decisive importance of air power, which had again been amply demonstrated by the success of Japan's opening military operations. Port Moresby was considered a potentially important base for Allied air operations, and its seizure for Japanese use was regarded as essential to avert a prolonged aerial stalemate in the southeast area, which would tax Japan's limited aircraft production resources.16
On 29 January an Army-Navy agreement embodying the main lines of the Navy's recommendations was reached in Tokyo, and the Army and Navy Sections of Imperial General Headquarters dispatched implementing orders to the South Seas Detachment and the Combined Fleet. These orders, which were identical in substance, read in part:
At this stage, no large concentrations of Allied troops had been observed in eastern New Guinea, and the number of enemy planes operating in the area was likewise known to be small.18 It was estimated that only two companies and one machine-gun platoon of Australian garrison troops were present in the Wau, Lae and Salamaua areas. The local operational agreement concluded between the South Seas Detachment and Fourth Fleet commands on 16 February, therefore, assigned only the 2d battalion of the 144th Infantry Regiment, plus one mountain artillery battery and other smaller units, to the Salamaua operation,19 while a naval landing force of approximately battalion strength was designated to occupy Lae.20 The invasion convoy was allotted a naval escort of one light cruiser, six destroyers, one minelayer and one seaplane tender, commanded by Rear Adm. Sadamichi Kajioka, and an additional supporting force of four heavy cruisers, two light cruisers and two destroyers, commanded by Rear Adm. Goto. It was agreed that the Navy's 4th Air Group, based at Rabaul, would provide the air support for these operations.21
Leaving Rabaul on 5 March, the invasion convoy skirted the south coast of New Britain and reached the scheduled landing points on the Huon Gulf on the night of 7 March, without incident. The landing forces went ashore early on 8 March, capturing Lae and Salamaua, with their adjacent airfields, against almost no opposition.22 Mopping-up and unloading operations progressed without interference until the morning of 10 March when approximately 60 American carrier planes and 16 bombers attacked the Japanese naval and transport ships at anchor and the Lae and Salamaua airfields. Considerable damage was sustained,23 but there were no further largescale Allied air attacks on this area until May.
From 12 March, naval landing force took over the defense of Salamaua, releasing the South Seas Detachment units which had carried out the landing operation. Naval units, according to plans, remained in charge of the defense of the entire Lae-Salamaua area, and all elements of the South Seas Detachment returned to Rabaul on 15 March.24 Small enemy forces, organized in guerrilla units, continued to operate from interior bases in the
vicinity of Mubo, southwest of Salamaua, and Gabmatsung, west of Lae. Occasional raids were carried out on Japanese sentry posts around Lae and Salamaua, but were not made in substantial force until late June.25
Although the Fourth Fleet, concerned over the gradual reinforcement of Allied air strength in Australia, had planned to carry out the scheduled operations against Port Moresby and Tulagi immediately after the capture of Lae and Salamaua, intervening developments forced a postponement. The Fourth Fleet was now without carrier support,26 and when an American Task Force suddenly appeared in the waters southeast of the Solomons about 20 February, the naval command at Truk decided that amphibious operations as far as Port Moresby and Tulagi supported only by the Navy's shore-based air strength in the Rabaul area would be too risky.27 These operations were consequently deferred until the Combined Fleet could again dispatch carrier elements to the southeast area.28
The Fourth Fleet nevertheless proceeded on its own initiative to carry out limited operations against the Admiralties and northern Solomons for the purpose of bolstering Rabaul and paving the way for the Tulagi invasion. On 30-31 March Navy forces landed in the Shortland Islands and at Buka and Kieta, on Bougainville. The Hermit Islands, Lorengau in the Admiralties, and Talasea on the north central coast of New Britain, were occupied on 7-8 Apri1.29 (Plate No. 30)
While the Port Moresby and Tulagi invasions were in abeyance, discussions between the Army and Navy High Commands on the whole issue of future operational policy regarding Australia came to a head. These discussions had been initiated by the Navy as early as February, following the invasion of the Bismarcks, but had produced no concrete results owing to a sharp divergence of opinion with the Army.
On the basis of its estimate that the United States Fleet would not recover from its Pearl Harbor losses quickly enough to assume the offensive in the Western Pacific before the end of 1942, the Navy, particularly the staff of the Combined Fleet, contended that Japan should not switch to a defensive policy of merely holding on to its already-established gains. A reversion to negative policies based on the original war plans, it was argued, would nullify Japan's early victories and invite a prolonged stalemate in which America's growing material strength would spell Japan's defeat.30
In support of this thesis, the Fourth Fleet command at Truk pointed to the gradually increasing flow of American war materiel, especially aircraft, to Australia, warning that this clearly indicated Allied intent to build up the subcontinent as a powerful counter-offensive base. Were this intent allowed to materialize, the Navy's existing defense line from eastern New Guinea to the Bismarcks and northern Solomons might prove inadequate to check an Allied counter-thrust.31 Consequently, the Navy insisted that Japan's wisest course lay in remaining actively on the offensive in the southeastern area, with the ultimate objective of attacking Australia itself.
In addition to these strategic considerations, the Navy proponents of an Australian invasion also advanced the political advantages to Japan of knocking Australia out of war and the added economic strength which would be gained through the acquisition of Australian wool, wheat, fertilizers and other resources.32
The dominant section of the Navy thus demanded a complete change-over from the original defensive concept of the southeastern front to one in which it would become a stepping-stone to further expansion. The Army Section of Imperial General Headquarters, however, strongly opposed over-extension of army commitments in that area and rejected the proposed invasion of Australia as a reckless undertaking far in excess of Japan's capabilities.33 Ground force strength required for such an operation was estimated at 12 combat divisions, which would strip other fronts considered more important by the Army. Also, Japan's available shipping, the Army contended, was unequal to the logistical task of transporting and supplying a force of such size.34
As a result of adamant Army objection, the idea of a direct assault on Australia died in the discussion stage.35 However, the Navy's insistence upon positive action to check the
growth of Allied strength in the southeast area36 led the Army to concur finally, by 28 April, in a compromise plan envisaging the occupation of strategic points in New Caledonia, the Fiji and Samoa Islands, to be carried out following execution of the deferred invasions of Port Moresby and Tulagi. As further steps to strengthen the Japanese strategic position and disrupt the flow of American supplies to Australia, the Navy had already ordered intensification of submarine warfare in the Pacific and Indian Oceans,37 and planned the early seizure of Nauru and Ocean Islands, west of the Gilberts.38
Preparations by the Fourth Fleet and South Seas Detachment for the Tulagi and Port Moresby invasions were already complete, and the start of the operations waited the impending arrival at Truk of a supporting Task Force dispatched by the Combined Fleet, including the 5th Carrier Division (Zuikaku and Shokaku) and the 5th Cruiser Division.39
Through the subsequent conquest of New Caledonia, Fiji and Samoa, in particular, the Navy planned to establish air and submarine bases which would enable it to command both air and shipping routes from the United States to eastern Australia. Special emphasis was to be placed upon stopping the ferrying of American aircraft to Australia via the South Pacific, and the destruction of tankers transporting fuel supplies. It was estimated that such a blockade, if effective, would retard, if not prevent, Australia's development into an Allied offensive base.40
Before any concrete operational plans were worked out for the New Caledonia-Fiji-Samoa invasions, however, Imperial General Headquarters on 5 May issued orders for the prior execution of operations against Midway and the western Aleutians.41 This crucial decision, which swayed the whole future course of the
war, was again taken at the strong insistence of the Combined Fleet and further influenced by the Doolittle raid on Tokyo of 18 April 1942.42
Although the decision to invade Midway and the Aleutians meant the deferment of the New Caledonia-Fiji-Samoa operations, joint staff planning for these operations continued, culminating in the issuance on 18 May of Imperial General Headquarters Army and Navy Section orders, which directed the Commander-in-Chief, Combined Fleet, and the Commanding General, Seventeenth Army, to:
On the same day that these orders were issued, the Seventeenth Army, with a nuclear strength of nine infantry battalions, was activated in Tokyo under command of Lt. Gen. Haruyoshi Hyakutake,44 and the Combined Fleet assigned the Second Fleet (with attached carrier forces) and Eleventh Air Fleet to the operations.45 The New Caledonia invasion force was to assemble at Rabaul in the latter part of June, and the Fiji-Samoa forces at Truk in early July. Dependent upon Combined Fleet commitments, the operations were tentatively scheduled for the first part of July.46
With the arrival of the 5th Carrier Division and 5th Cruiser Division at Truk on 29 April, the long-delayed seaborne invasion of Port Moresby at last got under way. Speed was essential because the Combined Fleet now planned to use these units in the subsequent Midway operation.
The final operations plans set the time of landing at dawn on 10 May, with the main South Seas Detachment forces to go ashore southeast of the Pari Mission and other elements (one battalion plus) to effect a secondary landing near the Barute Mission. (Plate No. 32) These forces were to attack the Kila Kila airfield and the Walter Peninsula immediately, while the beachheads were being secured by a battalion of the Kure 3d Special Naval
A source of some concern during the planning of the operations was the fact that the six Army transports assigned to carry the South Seas Detachment were old ships with a maximum speed in convoy of only 6.5 knots, which meant increased vulnerability to enemy air attack.48 To minimize this danger, the naval escort, which consisted of only the 6th Destroyer Squadron (six destroyers, one light cruiser) with five minesweepers and one minelayer, was reinforced by the addition of a support force comprising the aircraft carrier Shoho and the 6th Cruiser Division (four heavy cruisers, one attached destroyer) under command of Rear Adm. Goto. This released the 5th Carrier Division (Zuikaku and Shokaku) and the 5th Cruiser Division (three heavy cruisers and seven attached destroyers), under command of Vice Adm. Takeo Takagi, to operate as a striking task force against any enemy naval units which might attempt interference.
As a further move to strengthen air support, seizure of the Deboyne Islands, east of Papua, was scheduled prior to the Port Moresby invasion, with the object of employing them as a seaplane base from which to support the later landing.49 The Deboyne operation was assigned to a force commanded by Rear Adm. Kuninori Marumo, consisting of the 18th Cruiser Division (two light cruisers), with 12 seaplanes, two gunboats and two minesweepers.50 In addition, two submarines were dispatched to positions in the Coral Sea, and four others were dispersed along the eastern coast of Australia to await the probable emergence of an enemy fleet.
On 25 April the 25th Air Flotilla based at Rabaul51 began attacks against northeastern Australia. Three days later, part of its strength moved up to the Shortland Islands to expand its radius of action. The Tulagi invasion, scheduled as a prelude to the operation against Port Moresby, was successfully accomplished on 3 May, the Shoho support force covering the invasion.
On 4 May, after Vice Adm. Inouye, Commander-in-Chief of the Fourth Fleet, had transferred his headquarters to Rabaul from Truk, the Port Moresby invasion force sailed from Rabaul. The same day, the Zuikaku and Shokaku, en route from Truk, received reports of an American carrier-plane attack on the Tulagi beachhead and convoy anchorage. They proceeded southward at top speed but were unable to spot the American carriers due to bad weather.
At 0930 on 6 May, however, a navy search plane reported an enemy task force, including a carrier and two other large units believed to be battleships, moving south 450 miles from Tulagi. Later in the day a radio report was intercepted from an Allied patrol plane to the effect that the Deboyne landing force and the Port Moresby invasion convoy had been spotted. The Japanese Task Force and convoy escort were alerted to prepare for action, but no change in the invasion schedule was ordered.
Both the Japanese and American naval groups were now committed to an engagement.
Early on 7 May, a Japanese scout plane reported the American Task Force only 163 miles from the Japanese carrier group. The Battle of the Coral Sea had begun. (Plate No. 32) All the attack planes of the Zuikaku and Shokaku (18 figthers, 36 bombers, 24 torpedo planes) took off at 0610 for an attack, but at 0640 another scout plane reported sighting the enemy force approximately 150 miles southeast of the Louisiade Archipelago, indicating that the first report had been erroneous (the destroyer Sims and tanker Neosho had been reported as the "enemy Task Force"). The Japanese carrier planes, which could not be recalled, attacked these ships, sinking the Sims and setting fire to the Neosho, which pilots reported abandoned by its crew.
Meanwhile at 0550 on 7 May, three B-17s flew over the Port Moresby invasion transports, and at 0700, the Port Moresby invasion transports, with the Deboyne force and part of the escort and support forces, began withdrawing to the northwest. The 6th Cruiser Division and 6th Destroyer Squadron broke off from the convoy to maneuver for a night attack on the enemy fleet in conjunction with the task force closing in from the southeast.
At 0900, 75 planes from the American Task Force struck at the Shoho group escorting the Port Moresby invasion convoy. Concentrated torpedo and bombing attacks sank the Shoho at 0930. At this time the Japanese Task Force was still about 250 miles distant from the American carrier group.
The Zuikaku and Shokaku, though unable to launch a further daylight attack on the 7th, sent up 27 torpedo and dive bombers manned by crews skilled in night-fighting to search for the enemy carriers.52 These planes, however, were suddenly attacked by American fighters emerging from the clouds, and with darkness approaching they abandoned the search. Heading back to the carriers, the dive bombers passed directly over the enemy force but could not attack since they had already jettisoned their bombs.53
At dawn on 8 May, a scout plane again located the American force (now reported to include two carriers and one large unit, probably a battleship) on a bearing of 205 degrees 235 miles from the Japanese carriers. The Zuikaku and Shokaku immediately launched all 69 of their attack planes, which contacted the enemy group at 0920. Despite fierce antiaircraft fire and fighter opposition, the Japanese planes damaged the Lexington so severely that it subsequently was abandoned and sunk by American destroyers.54
Simultaneously, the Japanese Task Force underwent heavy attack by waves of enemy carrier planes from 0850 to 1020. The Shokaku, receiving three direct hits and eight near misses, caught fire and was unable to launch or receive planes, forcing the Zuikaku to accommodate all returning Japanese aircraft. By 1300, when the last plane was accommodated, it was found that only 24 fighters, nine bombers and six torpedo planes remained out of the total original complement of 36 fighters, 36 bombers and 24 torpedo planes, including both attack planes and fighters assigned to defense.
Due to these heavy losses and the fact that the Port Moresby invasion convoy was now without carrier protection, Vice Adm. Inouye
ordered the Task Force at about 1500 on 8 May to suspend the attack and head north. All units had turned about, when it was further learned that the Port Moresby landing had been postponed and the invasion convoy ordered back to Rabaul.
Vice Adm. Inouye's passive tactics, however, drew swift disapproval from Admiral Yamamoto, Combined Fleet Commander-inChief, who radioed orders "to make every effort to annihilate the remnants of the enemy fleet." The Task Force consequently turned south again and sought to re-establish contact, without success, until sundown on 10 May. The tactical advantage had been lost, and the Task Force withdrew.55
The Coral Sea battle, the world's first duel between aircraft carriers, had not resulted in a decisive naval victory for either side. However, Japanese plans for the speedy occupation of Port Moresby suffered a serious setback. Without high-speed transport and the support of powerful carrier forces, a new attempt at seaborne invasion could not be undertaken.56 The Combined Fleet, already committed to the Midway operation in June, could not spare its carrier forces and advocated postponement of any further attempt until July.57 Consequently, on 9 May, Imperial General Headquarters issued an army order stating:
If the Battle of the Coral Sea upset the Japanese plan to tighten the encirclement of Australia, the disastrous defeat suffered at Midway59 in the succeeding month of June 1942 dealt Japanese naval power a crippling blow that abruptly redressed the balance at sea in favor of the United States Fleet. Apart from the failure of the invasion attempt itself, the loss of the Combined Fleet's four carrier mainstays-the Akagi, Kaga, Soryu and Hiryu-against the sinking of a single American carrier, the Yorktown, meant the precipitate collapse of the hitherto superior Japanese carrier position and, consequently, of the combat strength of the Combined Fleet.
This disaster, the full extent of which was not revealed to the Japanese public, had swift repercussions on the southeast area front. On 11 June, four days after the Midway battle ended, Imperial General Headquarters ordered a two months' postponement of the New Caledonia-Fiji-Samoa operation, previously scheduled for early July, and one month later the operations were cancelled completely.60 At the same time attention forcibly shifted from a direct amphibious assault on Port Moresby, now deemed impracticable, to a possible land drive from the east coast of Papua across the
Owen Stanley Range.
The severe losses in carriers and aircraft suffered in the Midway battle, indeed, only served to increase the importance placed by the Army and Navy High Commands upon the capture of Port Moresby. More than ever, possession of this base was considered necessary to wrest from the Allies air control over the vital Coral Sea area, and to check the mounting threat of enemy air power not only to the Japanese outposts in eastern New Guinea but to the key stronghold of Rabaul itself.61
Simultaneously with the postponement of the New Caledonia-Fiji-Samoa operations, Imperial General Headquarters ordered the Combined Fleet and the Seventeenth Army (activated 18 May) to drop temporarily any plans for a second seaborne assault on Port Moresby and instead to begin formulating plans for a possible land drive. To facilitate this planning, elements of the Seventeenth Army62 were to occupy a section of the east coast of Papua along the Mambare River as a base for reconnaissance.63 This was designated as "Research Operation Ri-Go."
The Fourth Fleet, convinced that any future land or sea operations in the direction of Port Moresby required the establishment of air bases in eastern Papua, immediately began surveying the area to locate possible sites. On the basis of this survey, it was estimated that the airfield at Buna, about 60 miles south of the Mambare River mouth, could be expanded into a major base. Immediately thereafter, aerial photographic reconnaissance was made of the land route leading from Buna across the Owen Stanley Range to Port Moresby, and the Seventeenth Army, after conferring with the Fourth Fleet, ordered the South Seas Detachment on 1 July to prepare for a reconnaissance operation in the Buna-Kokoda sector to determine its suitablility as a staging area for a major land drive against the Allied base. The order stated:
Preparations for the movement of the reconnaissance force to Buna were still in progress when Imperial General Headquarters, going beyond the terms of its initial order, issued
a new order on 11 July stating that "the Seventeenth Army, in cooperation with the Navy, shall at the opportune time capture and secure Port Moresby, and mop up eastern New Guinea."65 This order made it clear that Imperial General Headquarters was no longer thinking in terms of a purely exploratory operation but had virtually decided upon an overland invasion of Port Moresby,66 for which the Buna landing force was to act as a probing spearhead. Reflecting this step-up in plans, Lt. Gen. Hyakutake issued the following order at Davao on 18 July:
Four days prior to this order, Maj. Gen. Horii, Commanding the South Seas Detachment at Rabaul, had ordered the Yokoyama Advance Force to prepare for the Buna landing and subsequent operations. This force, under command of Col. Yosuke Yokoyama, was made up of the 15th Independent Engineers, who had gained fame in the Malayan jungles, and the 1st battalion of the 144th Infantry, veterans of the Guam and Rabaul campaigns. After landing at Buna, the force's principal missions were to push to the southwestern slopes of the Owen Stanleys, secure a perimeter along this range, reconnoiter and improve roads, and build up supply depots in preparation for a drive on Port Moresby by the main body of the South Seas Detachment, to be landed later.68
Although the mission of the Advance Force was no more than exploratory reconnaissance, this remained necessary to later operations since the Japanese possessed virtually no information regarding the Papua interior. Military topographic surveys were non-existent, and hydrographic charts, containing data of little value to land operations, were the only operational maps available. Knowledge of terrain, climatic conditions and prevalent diseases was also lacking. The Yokoyama Advance Force therefore planned to undertake its advance relying largely upon native guides.
Aerial photographs taken by naval reconnaissance planes of the Buna-Kokoda-Moresby route and distributed to the Army units concerned were the most important contribution to pre-operation planning. These photographs, however, revealed only fragments of the junglehidden trail, and the information gleaned from them was pitifully inadequate.69 For example,
the orders to the Yokoyama Advance Force directed that the road north of the Stanley Range be improved for motor, or at the very least, for wagon traffic, and the road to the south of the range for pack-horse and if possible wagon traffic. Actually, the Buna-Moresby "road" was nothing but a native trail which alternately ran through jungle swamps and over precipitous mountains. Throughout the entire campaign the use of vehicular transport was out of the question.70
The final operational plans agreed upon between the South Seas Detachment and Fourth Fleet commands at Rabaul called for the execution of the Buna landing with a strength of about 3,600 Army and Navy personnel. The Yokoyama Advance Force, comprising 1,002 men of the 15th Independent Engineers, 855 men of the 1st battalion, 144th Infantry, a mountain artillery battery (200 men) and service units was to embark on two Army transports, while a third transport, the Kinryu Maru, was to carry a company of the Sasebo 5th Special Naval Landing Force (about 300 men) and the 15th Naval Construction Unit (about 800 men). The naval landing force was assigned the mission of securing the beachhead and the Buna Village area, and the construction unit was to begin immediate enlargement of the airfield.
The Rabaul-based 25th Air Flotilla, with 60 fighters and 48 bombers under its command, was ordered to provide air cover for the operation, while the 18th Cruiser Division (two light cruisers) under Rear Adm. Koji Matsuyama, with three destroyers and other smaller units, was assigned as naval escort. The landing was scheduled for 21 July.
On 20 July the convoy weighed anchor from Rabaul, undergoing an attack by American B-17 bombers during the run across to New Guinea. The Kinryu Maru sustained slight damage from five near misses but was able to continue in convoy to the Buna anchorage, where the invasion force arrived on schedule at 1600 on the 21st. The naval landing force went ashore three miles northwest of Buna at 1730, while the Yokoyama Advance Force began disembarking at Basabua, a short distance farther to the northwest, at 1900. No resistance was encountered, and within 14 hours of the landing, Buna Village and the airfield were securely in Japanese hands.71
Simultaneously with the Buna landing, the 82d Naval Garrison Unit holding Lae and Salamaua72 launched attacks on the Australian strongpoints at Gabmatsung Mission, about 18 miles west of Lae, and Mubo, about 15 miles southwest of Salamaua. The operations had been decided upon to put a stop to increasing guerrilla activities in these areas and were also timed to serve as a feint covering the Buna landing. At Gabmatsung the Australians promptly withdrew south of the Markham River, and the Japanese discontinued the action
on 22 July, returning to Lae. At Mubo, however, the Japanese attack force encountered resistance by about 200 Australian troops, who inflicted some losses before retreating to the south. The Japanese returned to Salamaua on 23 July, ending the operation.73
Meanwhile, at the Buna beachhead, the Japanese landing forces underwent heavy air attack on 22 July by approximately 100 Allied planes, including B-17's, B-26's and P-39's. These attacks continued daily thereafter, inflicting damage to one transport and a destroyer of the invasion convoy. Despite these attacks, additional troops were successfully put ashore from a destroyer on 26 July, and from two transports, a light cruiser and a destroyer on 29 July, but the unloading of war materials ended in failure.74
Due to the steady intensification of Allied air attacks, however, the transport of reinforcements to Buna became rapidly more perilous. On 30 July the transport Kotoku Maru had to be abandoned after receiving hits in a strike by eight Flying Fortresses. On 31 July, another transport en route to Buna under naval escort was forced to turn back to Rabaul due to air attack.75
Initial reports to Seventeenth Army headquarters by the Yokoyama Advance Force were optimistic. Immediately after the landing, a spearhead patrol of company strength set out along the trail to Kokoda, meeting only sporadic resistance from a small Australian force about 100 strong, which retreated before them. After dispersing these remnants, the patrol advanced as far as Oivi Hill, about nine miles east of Kokoda, where it was shortly joined by the main body of the Yokoyama Advance Force. Launching an attack on the night of 28 July, the Force routed the Australian 39th Battalion and moved into Kokoda at dawn on 29 July, occupying the nearby airfield at noon the same day.76
Although the capture of Kokoda was effected earlier than anticipated, the advance had not been without hardship. TheYokoyama Advance Force, in its rapid drive along the arduous jungle trail, had shed all excess equipment and rations, and when it reached Kokoda, the problem of bringing up food and ammunition assumed prime importance. To the rear, the engineers doggedly worked to widen and improve the trail and could not be spared to move supplies. This vital task therefore had to be undertaken by elements of the naval construction unit, which was engaged in improving the Buna airfield.
On the basis of the early reports sent in by the Yokoyama Advance Force, Lt. Gen. Hyakutake, whose headquarters had now moved to Rabaul, hastily advised Imperial General Headquarters that an overland attack on Port Moresby was feasible and recommended adop
tion of definite plans to move the main forces of the Seventeenth Army across the Owen Stanleys to effect the capture of this important base.77 The Army and Navy Sections of Imperial General Headquarters thereupon drew up the main lines of an operational plan, issued in the form of orders to the Combined Fleet and the Seventeenth Army on 28 July. The essential portion of these orders read:
Upon receipt of these orders, the Eighth Fleet79 and Seventeenth Army immediately began working out the details of the final plan reaching agreement on 31 July. The essential points of the plan were as follows:
These plans were ready to be put into execution when last-minute delay in the completion of the Buna airfield, followed by the sudden landing of American marines on Guadalcanal on 7 August, forced a postponement of the scheduled date for the debarkation of the South Seas Detachment main body at Buna until 16 August. It was estimated that, by that date, preparations for the recapture of Guadalcanal would be complete, and sufficient air strength would be available to cover the Buna landing operations.
Up to 7 August, when the American invasion of the Solomons began, the total number of Japanese troops and naval personnel put ashore at Buna for the Port Moresby operation approximated 7,430.82 Of these, 430 were naval landing troops, and 2,000 naval construction personnel. The remaining 5,000 represented the original Yokoyama Advance Force plus reinforcements and replacements sent in subsequent to the 21 July landing.
A radio dispatched to Eighth Fleet headquarters in Rabaul at 0530 on 7 August reported both Guadalcanal and Tulagi83 under heavy enemy naval and air bombardment. From the strength and make-up of the enemy naval force-two aircraft carriers, one battleship, three cruisers, 15 destroyers and 30 to 40 transports-it was evident that landings were contemplated.
The Japanese forces on Guadalcanal at that time numbered only 250 naval garrison troops and two construction units of about 1,600, stationed near Lunga Point.84 Before communications ceased, the Eighth Fleet received a report that they were retreating into the interior after engaging the enemy landing forces. Meanwhile, on Tulagi, the Japanese naval garrison of approximately company strength was believed annihilated.
Despite the success of the American landings, Imperial General Headquarters in Tokyo took the optimistic view that the operation was nothing more than a reconnaissance in force, and that, even if it were the beginning of a real offensive effort, Japanese recapture of Guadalcanal would not be excessively difficult.85 Reports were lacking from the Japanese forces on the spot, and the situation was vague.86
On the other hand, Admiral Yamamoto, Commander-in-Chief of the Combined Fleet, regarded the American counterthrust more seriously and promptly appointed Vice Adm. Nishizo Tsukahara, Commander of the Eleventh Air Fleet, as Commander of the Southeast Area Force, a new intermediate fleet command.87 First priority was given to the recapture of Guadalcanal, and all available ships and planes were assembled for an immediate and decisive counterattack.
While the 25th Air Flotilla threw all its operational strength88 into a series of damaging air assaults, the Eighth Fleet's most powerful combat ships, under personal command of Vice Adm. Gunichi Mikawa, Eighth Fleet Commander-in-Chief, sailed from Rabaul at 1430 on 7 August to attack the enemy vessels off Guadalcanal. In this attack (Plate
No. 35), carried out on the night of 8 August,89 heavy losses were inflicted on the Allied convoy force, and although the marine beachhead remained intact, active reinforcement efforts did not immediately develop.
The absence of further American attempts to send in troops was interpreted by Imperial General Headquarters as confirming the first estimate that a major offensive was not developing,90 and that recapture of Guadalcanal could be speedily achieved. Accordingly, on 13 August, a new operational directive was issued for the southeast area, stipulating that elements of the Seventeenth Army should be dispatched immediately to recapture Guadalcanal and Tulagi, and that "the invasion of Port Moresby shall be speedily carried out in accordance with previous plans."91
In order to seize the tactical opportunity before the enemy foothold on Guadalcanal could be consolidated, the Army General Staff advised employment of small forces which could be swiftly moved to the scene of action by destroyers, rather than an attempt to transport the Seventeenth Army's larger uncommitted units-the 35th Inf. Brigade at Palau, and Aoba Detachment at Davao.92 The Ichiki Detachment93 of approximately regimental strength, which had been placed under Seventeenth Army command on 10 August for use on Guadalcanal, was already at Truk. Hence it was decided to use this detachment plus a naval landing force in the initial recapture attempt.
Embarking from Truk on six destroyers, the main strength of the Ichiki Detachment landed on 18 August at Taivu Point, while a force of naval troops landed simultaneously at Lunga Point. The Ichiki Detachment launched a vigorous attack on the airfield area but were driven back in retreat west of the Tenaru River, Col. Ichiki himself having been killed. Not only had the attempt failed, but on 21 August it was confirmed that American planes had begun to operate from Henderson Field, while increasing numbers of troop reinforcements were landing from transports. Abruptly the situation darkened.
On 19 August, the day following the landing of the Ichiki Detachment main strength, the Seventeenth Army had issued new orders for the immediate advance to Guadalcanal of the remainder of the detachment plus the 35th Inf. Brigade,94 whose Commanding General (Maj.
Gen. Seiken Kawaguchi) was assigned to command all Army and Navy forces in the Guadalcanal-Tulagi area.95 As the transport groups carrying these forces moved south from Truk, powerful naval screening forces, including three carriers (Zutkaku, Shokaku, Ryujo), swept around the eastern side of the Solomons to divert and crush enemy naval and air forces. In the ensuing Second Battle of the Solomons,96 fought on 24 August, damage was sustained on both sides, the Ryujo going down under heavy attack by carrier and land-based aircraft. The transport convoy, which also underwent attack by enemy land-based bombers, was forced to turn back, and the reinforcement attempt failed.
In view of these developments, Imperial General Headquarters began to show increased concern over the Guadalcanal situation and, on 31 August, issued orders giving first priority to the recapture of the Solomons. In accordance therewith, efforts were pushed by the Seventeenth Army and Southeast Area Force Commands to get in reinforcements in preparation for a general offensive. Little by little, between 30 August and 7 September, night runs by destroyers and landing barges succeeded in putting ashore the remainder of the Ichiki Detachment and the entire 35th Brigade. In all, a total of about 5,200 troops were transported by this means subsequent to the enemy landing of 7 August.97
Despite the limited strength of these forces, plans were laid for the start of a general offensive on 11 September. The 35th Brigade was to launch a surprise attack on the American perimeter guarding Henderson Field, while a powerful naval force made up of the Eighth Fleet supported by elements of the Second and Third Fleets was to move directly up to the Lunga anchorage to cut off both possible reinforcements and enemy retreat.98
Owing to delay in bringing up artillery support and maneuvering all forces into position through the jungle, the general offensive did not begin until 2000 on 13 September. As the 35th Brigade troops pressed forward, they met increasingly severe resistance by the entrenched marines, and heavy losses finally forced them into retreat. Following this debacle, Maj. Gen. Kawaguchi decided to reassemble all the Japanese forces on the west bank of the Matanikau River. (Plate No. 37)
Despite two failures, the High Command still remained determined to recapture Guadalcanal at any cost. Preparations were consequently begun for the dispatch of still further reinforcements, upon the arrival of which another general offensive was to be attempted.99
In spite of the American invasion of the Solomons, the over-all strategic plan decided upon by Imperial General Headquarters on 28 July for the capture of Port Moresby remained unchanged during August. The Seventeenth Army, although obligated to furnish.
troops in support of Navy attempts to recapture Guadalcanal and Tulagi, was not relieved of its prior New Guinea commitments, and a radio from Imperial General Headquarters on 8 August instructed that the Port Moresby campaign be vigorously intensified insofar as the local naval situation permitted. Voicing concurrence with this directive, Lt. Gen. Hyakutake, in a report to Imperial General Headquarters on 9 August, stated:
The operational policy indicated in this exchange of views was formally confirmed by the Imperial General Headquarters directive of 13 August, which ordered that the operations against Port Moresby be carried out as already planned. The Navy's support of these operations, however, was inevitably limited by the channeling of its primary effort into the recapture of the Solomons, an area of more immediate Navy concern.
Under the 13 August directive, preparations for the scheduled movement of the main strength of the South Seas Detachment to New Guinea were speedily brought to completion. On the night of 13 August, three transports loaded with construction personnel, equipment, and supplies safely negotiated the crossing to Buna, where at the same time the finishing touches were being put on the enlarged airfield in preparation to receive fighter planes of the 25th Air Flotilla assigned to protect the landing area.101
The convoy carrying the South Seas Detachment headquarters and the remaining two battalions of the 144th Infantry Regiment reached the Basabua anchorage, northwest of Buna, at 1730 on 18 August without undergoing enemy air attack. Three days later, on the night of 21 August, the 41st Infantry Regiment (placed under South Seas Detachment command), less its 1st Battalion, also debarked safely at Basabua and immediately joined the general movement of the Detachment toward Kokoda. Virtually the entire strength of the South Seas Detachment was now deployed in New Guinea for the final assault on Port Moresby.102
While the main forces of the South Seas Detachment moved up to throw their weight into the drive across the Owen Stanleys, the Eighth Fleet, in compliance with the Imperial General Headquarters directive of 13 August, turned its attention to that phase of the joint Army-Navy operational plan which called for an amphibious landing to the east of Port Moresby in coordination with the land attack from the north.
It was apparent, in view of increasing Allied air strength in northern Australia and the Port Moresby area, that such an amphibious operation would have little chance of success unless an intermediate base at the southeastern tip of Papua were first acquired as a staging point for troops and supplies and as an air base for covering the movement of amphibious forces. The operational agreement of 31 July had merely called for the seizure of Samarai as a Navy seaplane base, but to cope with mounting Allied air power the Eighth Fleet now deemed it essential to acquire a base adequate for land-based planes. It therefore decided in favor of an amphibious assault on Rabi, strategically located on the north shore of Milne Bay.
According to Japanese intelligence, approximately 30 Allied fighter planes were already based in the Milne Bay area, operating from the Rabi airfield and new airstrips constructed to the west. It was also assumed that Allied defenses had been strengthened considerably, since there had been a noticeable augmentation of transport activity to that area from Australia. Nevertheless, it was believed probable that the area was not yet strongly held, and the Eighth Fleet proceeded to plan its attack without taking effective measures for preliminary reconnaissance. This omission was furthered by the current concentration of naval air strength in the operations to reinforce Guadalcanal.
The operation was to be a two-pronged assault, with the main force landing in the vicinity of Lehoa, about five miles east of Rabi, while a second force was to land at Taupota, seven miles northeast of Rabi on the shore of Goodenough Bay. (Plate No. 38) Two special naval landing forces were assigned to the main landing, and 353 men of the Sasebo 5th Special Naval Landing Force, then at Buna, to the secondary landing at Taupota.103 The latter were to move by landing barge down the coast from Buna and after debarking were to cross over the Stirling Mountains to take the enemy from the rear in conjunction with the frontal assault of the main force.
The Eighth Fleet plan called for the launching of the Milne Bay operation immediately upon the expected recapture of Guadalcanal by the Ichiki Detachment, which erected a counter-landing on 18 August. A report of the detachment's failure reached the Eighth Fleet Commander, Vice Adm. Mikawa, aboard
his flagship during the subsequent operations to move in the 35th Brigade. However, still confident that the recapture of Guadalcanal would be effected at an early date, Vice Adm. Mikawa dispatched orders to the 18th Cruiser Division, held at Rabaul in readiness for the Milne Bay operation, to begin execution of the attack plan without awaiting the outcome on Guadalcanal.
The forces assigned to the main landing sailed from Rabaul on 24 August, undergoing a light attack by about ten Allied planes as they neared Milne Bay on the afternoon of the 25th. The convoy, which entered the Bay late on the 25th, included two transports carrying 811 naval landing troops104 and 363 personnel of the 10th Naval Construction Unit, all under command of Comdr. Shojiro Hayashi. Two light cruisers, five destroyers and two submarine-chasers composed the naval escort.
The Lehoa landing was carried out with reasonable ease at 2150 on 25 August. The next morning, however, Allied planes suddenly attacked the beachhead, destroying a large part of the food and ammunition supplies which had been unloaded. As the landing force began moving forward toward the Rabi airfield, its main objective, enemy air strikes increased in intensity, making daylight movement impossible. Advancing by night over unknown terrain, the troops floundered through jungle swamps to reach the eastern edge of the airfield on the night of 27 August. Here they met such unexpectedly savage resistance by the Allied troops defending the airstrip that, at dawn on the 28th, it was decided to retire into the jungle and await reinforcements.
At 2100 on the 29th, 769 additional naval landing troops under105 Comdr. Minoru Yano landed slightly to the west of Lehoa and joined the initial force in a second advance on Rabi, which began at 2330 the same night. A diary account portrayed the optimistic mood in which the Japanese moved up for the attack:
On the following day, however, constant air attacks again pinned down the Japanese advance in the jungle, but with nightfall the attacking force succeeded in advancing to the eastern perimeter of the airfield, where it again met withering fire from the Australian defenders. Beginning at daybreak on 31 August, Allied tactical aircraft joined in the battle, and Japanese Navy fighters, hurriedly dispatched to the scene, were unable to gain air control.107
Eighth Fleet headquarters, recognizing the need of sending further reinforcements, alerted a newly-arrived naval landing force at Rabaul, but on 2 September, just as preparations began for their embarkation, Allied reinforcements were put ashore at Giligili, threatening the Japanese force from the rear. A radio dispatched to Eighth Fleet headquar
ters reported: "Situation most critical. We shall defend key position to the last man."108
It was now evident that the piecemeal commitment of small naval forces would not retrieve the situation, and that the circumstances called for large-scale army reinforcements. Accordingly, agreement was reached between the Eighth Fleet and Seventeenth Army to dispatch the Aoba Detachment, approximately 1,000 strong, to relieve the hard-pressed naval force at Milne Bay. However, the situation at Guadalcanal made it impossible for this plan to be put in to effect despite the above local ArmyNavy agreement. Consequently the naval forces were ordered to avoid major action and resort to delaying action.
Relentless Australian counterattacks, however, soon produced a situation in which it was clear that the battle was irretrievably lost. On 4 September, the Eighth Fleet issued orders for the withdrawal of all forces from Milne Bay, and the Seventeenth Army subsequently relieved the Aoba Detachment of its reinforcement mission, assigning it instead to Guadalcanal.109
Evacuation of the naval landing forces by one light cruiser and three patrol boats began on 5 September and was carried out with reasonably satisfactory results. Of the 1,943 troops landed on 25 and 29 August, 1,318 were eventually withdrawn.110 All of the survivors, however, were incapable of further combat due to sickness, wounds or battle fatigue, a testimonial to the bitter hardships they had been through.111
A contributory cause of the failure at Milne Bay was the fact that the planned rear attack from Taupota never materialized. The naval landing force assigned to this operation had sailed from Buna on 24 August aboard seven landing barges, but while temporarily anchored off the shore of Goodenough Island, the group underwent a concentrated Allied air attack which destroyed all seven barges, together with their radio equipment.112 Suffering from near-starvation and malaria, the survivors remained stranded on the island for two months, twice making desperate efforts to con
tact the Japanese forces at Buna by sending messengers across to the New Guinea coast by canoe.
When approximately 300 Allied troops began landing on the eastern and southern shores of Goodenough Island on 23 October, the plight of the Japanese unit became still more serious, although it retained sufficient strength to repulse the enemy landing force in the southern shore sector.113 Finally, using two landing barges which had been sent in response to its appeals to Buna, the unit withdrew to Upurapuro, on adjacent Fergusson Island, where it was picked up on 26 October by the cruiser Tenryu and evacuated to Rabaul.114
With the collapse of the Milne Bay invasion attempt and the steady deterioration of the situation on Guadalcanal, Japanese hopes on the southeast area front now centered on the advance of the South Seas Detachment, which had forged its way over the Owen Stanley Range almost within striking distance of Port Moresby.
After capturing Kokoda on 29 July, the Yokoyama Advance Force pressed forward into the Owen Stanley range on 7 August, meeting almost continuous resistance by a force of about 200 Australian troops. (Plate No. 39) From about 20 August there was a marked intensification of Allied air reconnaissance, followed by severe bombing and strafing attacks against the advancing Japanese column. On 26 August the Yokoyama Advance Force ran into stiff opposition by an enemy force of estimated battalion strength on the heights near Isurava, and as soon as the first elements of the South Seas Detachment, newly-arrived from the Buna beaches, were able to move up to the front line, the battle was joined.
Due to stubborn enemy resistance and difficulties encountered in moving up supplies over the steeply mountainous and junglecovered terrain, the initial attacks failed to dislodge the Australians from their strong position, and the advance was stalled until the arrival on 27 August of the 2d Battalion of the 41st Infantry, led by the regimental commander, Col. Kiyomi Yazawa. On the 29th the 144th Infantry threw its full strength into a combined frontal assault and enveloping attack around the enemy's right flank, succeeding after eight hours of bitter fighting in overrunning the Australian outer perimeter and part of the main enemy positions, but only at the cost of heavy casualties. On 30 August the 2d Battalion of the 41st Infantry successfully enveloped the enemy's left flank by a difficult advance over the mountains, and by the 31st the Australians were encircled and defeated with heavy losses. On 1 September the South Seas Detachment forces entered Isurava.115
Despite its own heavy casualties, the South Seas Detachment was heartened by its success and pushed on beyond Isurava, its progress becoming ever more difficult as it penetrated deeper into the Stanley Range. The hardships
of the advance were graphically recorded in this passage from a soldier's diary:
After suffering from the intense heat of the lower altitudes, the troops, as they climbed toward the summit of the Stanley Range, now began to suffer from the frigid nights and icy rains, against which their tropical battle-dress gave little protection. Still more serious was the appearance of shortages of rations and ammunition, partially resulting from a tendency among the foot-weary troops to lighten their packs during the gruelling advance. So alarming was the situation that Maj. Gen. Horii, in a special order issued 1 September, enjoined strict measures of economy:
Indeed, the problem of supply was the most critical one facing the Japanese forces pushing toward Port Moresby. It was now recognized that roads capable of accommodating vehicular traffic were non-existent. At best, in the jungle, troops could follow the native trails, tangled with undergrowth, but in the mountains these trails narrowed down to nothing more than forgotten tracks clinging precariously to the sides of cliffs, or vanishing perpendicularly into steep canyons.
In the course of its advance, the South Seas Detachment carved 20,000 steps in the mountainsides to facilitate its march, yet at the end of the operation it was still impossible to use even pack horses south of Isurava. Rains held up all transport for days at a time. Moreover, in good weather, Allied air attacks soon reached a degree of intensity which made it
impossible to move men or supplies during daylight hours.118
In addition to the obvious fact that the South Seas Detachment was outstripping its supply lines, Seventeenth Army headquarters in late August recognized the unwisdom of attempting a headlong advance on Port Moresby without regard for the progress of the parallel operation at Milne Bay, which was to pave the way for a coordinated amphibious assault. The situation at Milne Bay was critical, and plans were being formulated to send in the Aoba Detachment to turn the tide of battle. Dependent upon the success of this operation, it was planned to move part of the main strength of the 2d Division, scheduled to be transferred from Java, to the area for the projected amphibious assault on Moresby.119
Pending the execution of these plans, the Seventeenth Army decided to slow the advance of the South Seas Detachment so as to conserve and build up its combat strength for the final push from the Owen Stanleys. Accordingly, on 28 August, the following order was received by Maj. Gen. Horii from Seventeenth Army headquarters at Rabaul:
Meanwhile, in Tokyo, the thinking of Imperial General Headquarters had also undergone a marked change since its 13 August directive calling for swift execution of the Port Moresby campaign "in accordance with previous plans". The failure of the initial attempts to recapture Guadalcanal, which indicated that the American foothold was considerably stronger than at first estimated, led to a shift of emphasis to the Solomons, where Imperial General Headquarters now foresaw the probable necessity of committing a large portion of Seventeenth Army strength previously intended for New Guinea.
The Army Section of Imperial General Headquarters therefore reached the decision that the strength of the Seventeenth Army should not be further expended in New Guinea until the recapture of the Solomons was assured. In accordance with this decision, a radio to the Seventeenth Army on 29 August explicitly directed that the South Seas Detachment halt its advance at the southern edge of the Owen Stanleys,121 and on 31 August a formal Imperial General Headquarters directive stipulated that major operations in New Guinea
would be held in abeyance pending the cleanup of the Solomons. The latter order stated:
This order came as a severe blow to the South Seas Detachment. In particular, it meant that the Detachment could continue to expect no naval air support of its operations. Although Navy fighters had operated briefly from the Buna airstrip to cover the landings of the main Detachment forces, they had soon been diverted to Guadalcanal, with the result that Allied aircraft dominated the skies over New Guinea, hammering constantly at the Japanese ground troops as they advanced and disrupting their supply lines to the rear.
Nevertheless, the troops on the Isurava front, encouraged by their successes of late August, pushed on toward the summit of the Stanley Range with the main body of the 41st Infantry spearheading the advance. On 1 September the 41st vigorously attacked the Australian position at Camp Gap, held by a force of approximately battalion strength, and succeeded in taking it by 0400 the following day. At dawn on 3 September, Eora was penetrated after three separate charges. The 41st Infantry drove on, meeting scattered opposition from the Australians who retreated to still another defense position estimated to be at the summit of the range. Throughout 4 September the 41st Infantry prepared for the assault, which was launched after nightfall. By 0200 5 September, the summit was in Japanese hands.
In the fighting from Camp Gap to the summit, the first Infantry had lost 44 killed and 62 wounded, but it had also inflicted considerable losses on the Australians, whose combat strength was estimated to be greatly reduced. Large amounts of abandoned stores were found during the advance from Camp Gap, and it was noted that the Australians were no longer using the main road in their retreat.
At this juncture a sudden intensification of Allied air strikes against the Buna area, coupled with intelligence reports of the presence of American air borne troops in Australia, led to fears that the enemy might be contemplating amphibious or airborne landings in that area in order to cut off the South Seas Detachment from the rear. To meet this threat, the Seventeenth Army on 8 September ordered Maj. Gen. Horii to reassemble the 41st Infantry Regiment at Kokoda, and a further order on 14 September directed that one battalion of the 41st Infantry be stationed near Buna to assure the defense of that area.
Meanwhile, the 144th Infantry Regiment, which had relieved the 41st at the front on 5 September, pushed off from the summit in the wake of the retreating Australians. Morale was high with the goal of the Moresby plain not far away, and the men advanced thinking of the ancient battle of Hiyodorigoe, famed in Japanese history and legend.123
On a hill south of Efogi, the 144th Infantry encountered its first stubborn opposition from the Australians, who were supported by heavy mortar fire. Sustaining considerable losses, the regiment was held up for three days until 8 September, when enemy resistance was finally overcome. After the battle, a company com
mander recorded in his diary:
Despite its heavy casualties, the regiment moved forward past Efogi, meeting scattered resistance from an Australian force in the hills south of the Nauro River and then advancing to attack strong enemy positions on a hill south of Ioribaiwa. "Climbing breath-taking hills and wading through muddy swamps"125 to reach Ioribaiwa, the exhausted troops, after close-quarter fighting and severe losses to both sides, finally penetrated the enemy position at 1530 on 16 September.
That night the troops, footsore and spent, could see searchlight beams from one of the Allied airstrips around Port Moresby, and they knew that only one more ridge separated them from the Moresby plain. But the 144th, like the 41st, had paid a heavy price for its gains. Battle casualties were high, with little means of transporting the wounded back the trail to base hospitals. Malaria was rampant. The men's nerves were shattered by constant enemy air attacks. Above all, rations were exhausted,126 and the troops near starvation. Just after the capture of Ioribaiwa, an officer wrote:
In view of the exhausted, semi-starved condition of its troops, aggravated by the completely inadequate trickle of supplies from the rear, the South Seas Detachment would hardly have been capable of further offensive action had it been called upon to continue the advance. However, with the capture of Ioribaiwa, it had fulfilled its restricted mission of pushing the enemy from the Owen Stanleys and establishing a foothold at the southern edge of the range. Now, its task was to consolidate its position, regroup its forces and prepare for the final drive on Port Moresby to be launched as soon as the American thrust into the Solomons had been overcome. On 20 September, Maj. Gen. Horii set forth the Detachment's future mission in the following message of instruction to all troops under his command:
Pursuant to Maj. Gen. Horii's message of instructions, the South Seas Detachment prepared to consolidate its hard-won positions on the southern slopes of the Stanley Range and simultaneously regroup its forces for the later assault on Moresby. However, crucial developments on other sectors of the southeast area front outdated this plan even before its execution began.
On Guadalcanal, the first general offensive of the 35th Inf. Brigade on 13 September had failed, and the Seventeenth Army was now preparing to commit its remaining reservesAoba Detachment and main strength of the 2d Division, previously intended for the final campaign against Moresbyin a second general offensive in October. At the same time, in New Guinea, Japanese supply difficulties became more acute, and there were mounting indications that General MacArthur planned early landings in the Buna area, which would, if successful, seal the fate of the South Seas Detachment and doom the entire Port Moresby invasion plan.129
Faced by this new situation, Seventeenth Army headquarters saw no alternative but to divert a substantial portion of South Seas Detachment strength back to the Buna area to counter enemy landing attempts. Consequently, on 23 September, the following order was dispatched to Maj. Gen. Horii:
Two main points of operational policy were clear from this order. The first was that the Seventeenth Army intended to suspend positive operations in the Owen Stanleys sector until Guadalcanal had been recaptured. The second was that the Army still desired to hold the Isurava-Kokoda sector, north of the Owen Stanleys, as a staging area from which to mount an ultimate attack on Port Moresby; but its major concern was now to secure the vital Buna area against threatened enemy attack, if necessary at the cost of relinquishing the vantage points gained by the South Seas Detachment almost within striking distance of Port Moresby.
Maj. Gen. Horii and his staff, conscious of the sacrifices paid to win possession of these vantage points, doubted the wisdom of relinquishing them. However, the Army order to move the 41st Infantry Regiment, which now composed the main combat strength of the Detachment,131 immediately back to the Buna area, rendered it necessary to pull the Detachment front line back from Ioribaiwa to a point closer to Isurava and Kokoda. After a nightlong staff conference, Maj. Gen. Horii on 24 September ordered the weakened remnants of the 144th Infantry to begin the withdrawal to Eora.132
On the 25th, headquarters personnel, supply and hospital units began moving to the rear, followed on the 26th by the combat troops, who withdrew under constant mortar fire from enemy positions. Active pursuit by the Australians did not begin immediately, however, and no enemy ground attack was received until the 144th Regiment had pulled back to the area south of Eora. (Plate No. 42) There, the 2d Battalion, with a mountain artillery battery and engineer company attached (henceforth designated as the Stanley Detachment) took up a strong position near Eora and covered the withdrawal of the remaining elements of the regiment. The latter completed their movement to Kokoda by 4 October.
Meanwhile, the 41st Infantry Regiment, less the 2d and 3d Battalions, had left Kokoda on 25 September arriving in Buna on 28 September, at which time the 3d Battalion rejoined the Regiment and by 4 October the Regiment had taken up defensive positions in the Buna-Gona-Giruwa area. The 2d Battalion remained at Kokoda with the main strength of the 144th Infantry to serve as a reserve force. These new dispositions were substantially
confirmed by a Seventeenth Army order on 30 September, which directed Maj. Gen.Horii:
However, beginning early in October, Australian attacks on the position held by the Stanley Detachment at Eora mounted in severity. Mercilessly pounded by enemy mortar fire and constant attacks from the air, the unit suffered extremely heavy casualties,134 and its position was rapidly becoming untenable. On 14 October, to save the Detachment from annihilation, Maj. Gen. Horii ordered the 144th Regiment less 2d and 3d Battalions back to the front, from which they had been withdrawn only ten days earlier. Even after these troops had reached Eora, however, the situation was so critical that the 3d Battalion of the 144th Regiment and 2d Battalion of the 41st Regiment, still in reserve at Kokoda, was ordered to prepare to cover the further withdrawal of all front-line forces by 25 October.
Already forced to withdraw to a new position north of Camp Gap on 21 October, the Stanley Detachment again attempted to make a stand, only to sustain further Australian attacks which steadily mounted in ferocity. The defense of the Gap soon became so precarious that Maj. Gen. Horii, on 24 October, ordered the main body (1st and 3d Battalions) of the 41st Infantry guarding the Buna-Gona area, to move up to the front again for the purpose of relieving the battered Stanley Detachment. Two days later, on 26 October, a further order by Maj. Gen. Horii conceded the probable necessity of a retreat as far as Oivi, relinquishing Kokoda to the enemy. The order stated:
Two days following this order, a Seventeenth Army dispatch on 28 October advised an even further withdrawal to the east bank of the Kumusi River, but Maj. Gen. Horii and his staff rejected this as unwise on the ground that the low terrain east of the Kumusi was unfavorable both for defense and as the starting-point of future offensive operations.
In accordance with Maj. Gen. Horii's order of 26 October, the Stanley Detachment and the 1st and 3d Battalions of the 144th Infantry hastily pulled out of their position near the Gap on 28 October, the 2d Battalion of the 41st Infantry covering their withdrawal. The plan was now to establish a strong north-south
defense line at Oivi, with the 41st Infantry on the right flank around Oivi itself and the 144th Infantry on the left flank slightly to the south, guarding a secondary trail from Kokoda to the Buna area. South Seas Detachment headquarters was to be at Gorari, approximately three miles east of Oivi.136
All dispositions were complete by 2 November, when the 41st Infantry's 2d Battalion fell back to Oivi, joining the 1st and 3d Battalions which had moved up from the Buna-Gona area. The Stanley Detachment and most of the remaining strength of the 144th Infantry meanwhile took up their left-flank position to the south of Oivi. The stage was set for battle.
The Australian forces now split into two elements, the first advancing on Oivi in a frontal assault while the second swept to the south in a flanking movement, launching a surprise dawn attack on 5 November against the 144th Infantry position. Driven back by the unexpected weight of the enemy assault, the 144th began retreating eastward on 9 November, crossing the Kumusi and heading toward Buna. The Australian force then wheeled swiftly northward to attack the 41st Regiment from the rear and cut off its retreat at Gorari.
Caught between the closing Australian pincers and cut off from contact with the 144th Regiment, the 41st, together with South Seas Detachment headquarters, found itself under heavy fire and facing imminent danger of encirclement. On 10 November Maj. Gen. Horii decided to withdraw toward the Kumusi under cover of a daring night attack against the eastern prong of the enemy pincers at Gorari to open a retreat passage. Preparations for a full-scale attack could not be completed in time, however, and a preliminary attack by two companies on the night of the 10th failed to breach the enemy positions. Maj. Gen. Horii then ordered the 41st Regiment to cross Oivi Creek, skirt around the northern enemy flank, and recross the creek farther to the east to get back on the trail to Buna. The withdrawal began at 0900 on 11 November.
Although the Japanese troops successfully crossed to the north bank of Oivi Creek on the 11th, heavy rains on the afternoon of that day flooded the creek to such an extent that attempts to recross to the south bank after skirting around the enemy at Gorari proved unsuccessful. Maj. Gen. Horii and his troops therefore continued to retreat along the north bank of Oivi Creek toward its juncture with the Kumusi River. They still had not succeeded in effecting a crossing when the approach of pursuing Australian troops on 13 November forced them to turn northward and flee along the trackless west bank of the Kumusi toward Pinga.
As the Japanese troops approached Pinga, the sound of gunfire was heard from across the river in the direction of Gona, and it was feared that the anticipated Allied landings had already taken place. Maj. Gen. Horii, gravely concerned over the situation, decided to attempt to reach the Buna area by canoe down the Kumusi. Setting out on 19 November with a staff officer and a runner, he succeeded in reaching the mouth of the river, and from there the canoe headed down the seacoast toward Buna. When directly off Gona, a sudden squall arose and capsized the canoe. Attempting to swim ashore, both Maj. Gen. Horii and his staff officer were drowned.
The 41st Infantry Regiment at Pinga, under the regimental commander, Col. Kiyomi Yazawa, had meanwhile built rafts, crossed the Kumusi River and started overland toward Gona. Losing many additional men and abandoning a large part of their weapons and equipment in the difficult overland trek, the depleted rem
nants did not reach the Gona area until 27 November.137
The 144th Regiment, after its hasty retreat from the Oivi sector on 9 November, withdrew northeastward toward Giruwa. Most of its remaining troops reached the Giruwa area by 17 November, only two days before strong American and Australian forces suddenly attacked from the sector south of the Buna airstrip.
Without time in which to reorganize its command and regroup its scattered, demoralized and weakened forces, the South Seas Detachment was now called upon to resist a powerful Allied pincers assault which threatened to wrest from the Japanese forces their last remaining foothold in Papua.