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The Japanese Strategy for New Guinea

After the setbacks at the naval battles of the Coral Sea and Midway in May and June 1942, the Japanese planned to secure Port Moresby to protect their base at Rabaul, to enable an expansion of operations to the north of Australia, and to blockade the supply routes in the region. The operation was not, however, based in sound research, especially concerning the stability of lines of communications and logistical support.

The decision was taken to undertake the campaign regardless of these difficulties. The offensive on Port Moresby commenced with the landing of the Yokoyama Advance Force at Buna and Gona on 21 July. Later, the South Seas Force, based on the 144th Infantry Regiment, landed with the intention of invading Port Moresby over the Owen Stanley Range via the village of Kokoda.

By mid-1942, the Allied presence in Port Moresby had grown from a relatively small, poorly equipped and defended outpost. It was, however, along with the developing base at Milne Bay at the east of Papua, the jumping point for aerial attacks on the main Japanese base at Rabaul. Occupation of Port Moresby by the Japanese would remove this immediate threat and provide a springboard of their own for continued raids against Allied bases in the north of Australia, and for disruption of supply routes in the area.

The setbacks at the battles of the Coral Sea and Midway in May and June resulted in the postponement of the planned Japanese naval advance to Fiji, Samoa and New Caledonia (FS Operation). The Army Section of Japanese Imperial GHQ responded by ordering the 17th Army to study the feasibility of conducting an overland offensive against Port Moresby (Ri Operation Feasibility Study).

The South Seas Force, under the command of Major General HORII Tomitarô, had provided the main strength of the successful invasions at Guam in December 1941 and Rabaul in January 1942. Since the failure of the May sea-route offensive against Port Moresby, the South Seas Force had been attached to the 17th Army, and was subsequently ordered to undertake the overland offensive. The 1st Battalion of the 144th Infantry Regiment joined the 15th Independent Engineer Regiment and other support units to form the Yokoyama Advance Party.

The main concern for planning, despite the obvious deficiencies of materiel strength and air-support over the planned battlefield, was logistical: could a force be supplied and marched across the rugged mountains with sufficient strength at the end to defeat a growing Allied presence at Port Moresby? Major General HORII expressed to his superiors at the end of June that he felt the task would require too great an investment in manpower to transport the required food, munitions and other supplies unless a substantial part of the distance could be traversed by vehicle.

The geography of the proposed route from Buna on the north coast, through Kokoda in the rugged Owen Stanley Range and on to Port Moresby, was determined from local testimony, documents, maps, and aerial reconnaissance photos. The evidence available to Staff Officers of the 17th Army was inconclusive as to the existence and quality of roads over the mountains. Despite this, the misjudgement that a vehicular road could be available for supply from Buna to Kokoda had disastrous consequences later in the campaign.

The 17th Army sought cooperation from the 4th Fleet, who assigned Rear Admiral MATSUYAMA Kôji to command the 18th Flotilla (Tenryû and Tatsuta) and the 29th Destroyer Squadron (Asanagi, Yuzuki and Uzuki). The transportation of men, horses, vehicles and supplies from Rabaul to Buna would be undertaken by the high-speed transports Ryoyo Maru and Ayatozan Maru. Aerial protection for the transports and landings were provided by the 25th Air Flotilla and the Tainan Air Corps.

The main strength of the South Seas Force remained at Rabaul to prepare for transportation to Buna in mid-August. It was originally formed around the 144th Infantry Regiment and support units from the 55th Division. It had also acquired additional engineer, marine transport, communications and water supply units to provide specific services in the jungles and mountains of the Owen Stanley Range.

On 15 July, one week before the planned departure of the Advance Force, 17th Army Headquarters was advised to proceed with the overland offensive without waiting for the results of the feasibility study. Imperial Headquarter's Staff Officer TSUJI Masanobu was sent to Davao and then Rabaul to make arrangements for these operations. The determination to proceed with the offensive was made on his own authority, but was soon followed by detailed army orders.

The Yokoyama Advance Force, along with one company of the Sasebo Special Naval Landing Party and naval base unit troops, effected a successful landing in the Buna and Gona areas in the evening of 21 July. They met little resistance and soon pushed inland to prepare roads and supply lines for the imminent advance of the main strength of the invasion force.

HORII supply proposal

In mid-June 1942, during the early planning phase for the overland operation to capture Port Moresby, the commander of the South Seas Force, Major General HORII Tomitarô, and his Chief of Staff, Lieutenant Colonel TANAKA Toyonari, met with staff of the 17th Army Headquarters at Davao in the Philippines to discuss the operation. HORII was unenthusiastic about the prospects of the success of the mission, and reportedly gave the following assessment to his superiors.

The South Seas Force will identify the best route from Buna through Kokoda to Port Moresby. From Buna to Kokoda is approximately 100 kilometres as the crow flies, but is in fact around 160 kilometres. Likewise, Kokoda to Port Moresby is 120 kilometres direct but is judged to be around 200 kilometres actual distance. In short, this route requires over 260 kilometres of trudging.

The problem is securing supplies. This would not be an issue if there was a road suitable for motor transport. However, without so much as a pack-horse trail, the actual conditions will require all supplies to be transported by human carriers.

The current number of men on the front line would be approximately 5,000. Given an average daily food requirement of 600 grams per person, this would result in a daily supply requirement for the Force amounting to 3 tonnes. If each man could carry 25 kg of supplies, this would limit a days march in the mountains to 20 kilometres.

A round trip march to the front line would take 20 days if the Force were to advance to the saddle of the Owen Stanley Range approximately 100 kilometres from Buna. Given that supplies for each soldier would be depleted by 12 kg after 20 days, the amount he could deliver to the front line would be 13 kg.

Securing the daily 3 tonne supply for the Force would require approximately 230 carriers per day reaching the front line. This amounts in total, given the 20 day round trip, to a requirement for approximately 4,600 carriers. If the front were to advance to Port Moresby, some 360 kilometres distant from Buna, then to supply food alone would require 32,000 carriers.

If one considers munitions and other supplies, the requirement for carriers would be immense. Ultimately, the overland route is probably not possible unless a road for motor transport can be pushed out from Buna.

Training

In order to prepare for landing and fighting in New Guinea, Japanese troops received various levels of training depending on their expected roles.

The soldiers who were going to land in New Guinea for the Port Moresby attack were to carry all their provisions (including 12 kg of rice) as well as their full equipment. Thus, their main training in Rabaul was to march with heavy loads on their backs. KANEMOTO Rinzô, a member of the supply company, recalled that soldiers spent many days marching with sacks stuffed with volcanic ash in their backpacks.

In contrast, 1st Class Private ISHIGURO Kiyoichi, who was captured near Papaki Bridge by the Allies in November 1942 only ten days after landing in New Guinea, listed a comprehensive range of training he had received in Sumatra. In addition to routine training in marching and handling arms, his training included rifle firing in various positions and range practice. Drills to handle gas masks were also carried out. They also went through assault exercises of attacking an enemy who has taken cover. Furthermore, in Sumatra, his company had comprehensive training on how to attack the enemy, including: bayonet and hand-to-hand fighting, daylight raiding exercises, dummy-grenade throwing, machine-gun firing and night and day landing operations.

YAMADA Kazuo was a 1st Class Private and pack-horse leader. When in Palau in May 1942, he received no training ashore, but had ship-board drills against submarine attack. After he arrived in Rabaul in June 1942, his training included climbing up the volcano in Rabaul with pack-horses.

TAMURA Hikoichi was a 22 year old Superior Private who was captured in Oivi on 11 November 1942. He was a member of 55th Engineer Regiment 1st Company which was attached to the 144th Regiment. The main training he received was in trench digging and road building. He said that bridge building was left for older soldiers with longer service. He told Allied interrogators that in spite of receiving drills with rifle and bayonet, his training was for defence rather than for attack.

In spite of various levels of training, the Japanese troops did not have the sufficient knowledge or skill to adapt to jungle warfare in New Guinea. They found it difficult to cope with the problems which were caused by disease and scarce supplies.

Equipment

In an ordinary situation, a full kit for a Japanese infantry soldier weighed about 28 kg. It consisted of a rifle with 120 rounds, a gas mask, a water bottle, two hand-grenades, a steel helmet and camouflage net, a set of uniforms, one pair of shoes and provisions consisting of four bags of iron rations and six kilograms of rice. However, special adjustments needed to be made for the Port Moresby attack. For example, the amount of ammunition to be carried was reduced to sixty or thirty rounds according to their tasks, and gas masks were not brought to New Guinea.

The most difficult aspect of logistics for the attack was how the troops could secure their supplies. The conclusion was that each soldier would carry 12 kg of rice to last for twenty days. In Rabaul, wooden back carriers, in the similar style used by farmers, were constructed on the spot by soldiers themselves. The total weight of the load was as heavy as 49 kg. For the machine gun unit, packs were heavier still and weighed up to 56 kg. Since those items needed to be piled up on the carriers, the top of the pack was 30 cm higher than a soldier's head.

Each unit transported different equipment to carry out their tasks. TAMURA Hikoichi was a 22 year-old Superior Private who was captured in Oivi on 11 November 1942. He was a member of 55th Engineer Regiment 1st Company which was attached to the 144th Regiment. He told his interrogators that each section in his company, which consisted of twelve men, carried a set of equipment for engineering work: including four shovels, three picks, one axe, one hatchet, one hammer, one pair of wire cutters, and one large saw to cut down trees. In addition, nails and staples were carried by each man. A shortage limited ammunition to only thirty rounds per man.

YAMAMOTO Tarô, 1st class Private in the 3rd Artillery Platoon of the 3rd Battalion of the 144th Regiment, was captured by the Allies on 3 October 1942 at Ioribaiwa. In interrogation sessions, he stated that each soldier in his unit carried sixty rifle rounds. Native carriers recruited in Rabaul carried supplementary supplies of ammunition.. In addition, each soldier carried two shells for battalion guns. Each shell was 50 cm in length, 5 cm in diameter, and weighed about 8 kg. A Type 94 Mountain Gun, which had a total weight of 530 kg was also transported as the troops advanced towards Port Moresby. It could be separated into pack loads, but it still would take seventy-two "healthy and strong" soldiers to transport it manually over the mountain.

Packhorses were used to carry loads of about 80 kg up to Kokoda. A typical load for a horse was ten pairs of wire cutters, five coils of rope, 1800 rounds of machine gun ammunition, and 800 round of SAA ammunition. Beyond Kokoda, they could not use horses due to the rough terrain, and the soldiers needed to carry the load on their backs.

Lack of information on the type of terrain they had to cross could be symbolised by the fact that two companies in the 1st Battalion of the 144th Regiment carried thirty bicycles each as IGAUE, Tokio, 1st Class Private who was captured near Papaki on 15 November 1942 stated in an interrogation report. The bicycles did not prove to be totally useless as sick soldiers rode them on some of the way, but they were eventually abandoned as the road condition became too rough and muddy for bicycles.

Morale

The morale among the troops was high as the South Seas Force was getting ready for the Port Moresby attack across the Owen Stanley Range. After the Force left Shikoku in late November 1941, the troops had series of extraordinarily successful campaigns. Their attack of Guam on 10 December 1941 and its subsequent occupation went smoothly. On 22 January 1942, the landing in Rabaul was successfully carried out without many Japanese casualties. After experiencing these impressive victories within a short time since the Pacific War began the South Seas Force had begun to feel invincible.

Some Japanese troops, however, were aware that the Australians would not be easy to beat. They acknowledged the considerable logistic advantage of the Allies in supplies, weapons and ammunition. Furthermore, they were aware that the Australians were formidable foes in combat - after the Force's advance party encountered strong defence by the Australians at Kokoda, the main contingent was cautioned that "The fighting spirit of the Australian infantry soldier is strong". Furthermore, the Australians' fighting spirit was regarded to be superior to that of the American troops in the area and their skills in marksmanship and use of cover and grenades were acknowledged.

The Japanese Army believed that its fighting spirit was much superior to the Allied soldiers and that the mental power of Japanese soliders would manage to overcome the obvious disadvantages in material power. General ADACHI, Commander of the 17th Army, called it "the unique and peerless spiritual superiority of the Imperial Army". The belief that strength of the spirit would overcome any type of difficulty and that it would eventually bring about victory was corrected to a certain degree after their defeat and withdrawal from Buna in January 1943. The appreciation which was written after those battles acknowledged the importance of providing supplies to the combat soldiers, but it still emphasised the importance of mental power. The 13th point of the general items of the appreciation stated as follows:

13. It is especially important for soldiers to train their mental power and boost their morale in order to carry out the campaign when they have to endure all types of difficulties and overcome disease. It is needless to say that strength and health are required, but those without sufficient mental power would often became ill and die within a short time.

In contrast, some of the soldiers on the ground had more realistic views on the cause of their defeat. IGAUE, Tokio, 1st Class Private in the 144th Regiment who was captured near Papaki on 15 November 1942, pointed out two reasons for their defeat to his Allied interrogator. According to him, the Japanese force underestimated the Allied strength and could not get supplies. (ATIS IR-17)

The obvious fact that morale of the soldiers could be sustained only with sufficient supplies of food and weapons was not appreciated properly throughout the war, and caused horrendous casualties among Japanese troops. Often, campaign plans were ordered to proceed without well established logistics support which would secure supply of weapons, ammunitions and most importantly, food to its troops.

Reconnaissance by KANEMOTO Rinzô

Maintaining supply proved one of the great difficulties for the Japanese in campaigns conducted in the relatively unknown area of Papua. The condition of pre-existing roads inland from the coast, and the distance that these could support vehicular traffic, was a vexed problem for South Seas Force Headquarters prior to the landing of the advance party in July 1942.

Evidence from initial investigations led to a determination that native trails led to Kokoda along the Manbare and Kumusi Rivers, and that a pack-trail existed from Buna to Kokoda. Aerial reconnaissance by planes from the 25th Air Flotilla based at Rabaul on 27 and 30 June discovered what seemed to be a vehicular road between Buna and Kokoda. The following report was consequently telegraphed to related units.

There exists a 2 or 3 metre wide track along the Mambare and Kumusi rivers for approximately 5 kilometres inland, and a 1 metre wide track for a further 10 kilometres. Thereafter a road was not detected due to thick jungle.

There is a road passable by motor transport between Buna and Kokoda. There is a bridge over the Kumusi River passable by motor transport to the east of Papaki. This road is in flat terrain devoid of ravines.

Detected a prominent road winding through the rugged valleys between Kokoda and Fada (mountains north of Isurava – author’s note). Determined areas passable by motor transport and areas where difficulties would arise.

This road emerges from Fada at the summit of the mountain, and then runs west along the Waume Creek (probably the Brown River – author’s note) until it disappears in the clouds. It is judged to be a road passable by motor transport that proceeds to Port Moresby.

No other prominent roads were detected in the area.

The unit responsible for arranging vehicular supply for the South Seas Force was the 55th Regiment Supply 2nd Company. Lt KANEMOTO Rinzô, a platoon leader with the Supply Company, was dispatched as an observer on the second of these reconnaissance flights. It was his first time in a plane, and after circling over what looked like Giruwa for several minutes, he lost all sense of direction. From an altitude of one to two thousand metres, however, it was impossible to tell how wide or in what condition was the ribbon-like road that wound in and out of the jungle to the south of the proposed landing position. The appearance of several Allied P-38s, though engaged by the five escort Zero fighters, only added to KANEMOTO’s sense of confusion.

His report to HORII, the Force commander, as follows, was consequently quite unsatisfactory.

Unfortunately, I cannot report with any confidence. There is certainly a road from Giruwa. That is all I can confirm. Only after landing can it be determined if it is suitable for vehicular traffic.

After further aerial reconnaissance, 17th Army Headquarters determined that while it was essential to investigate and improve the condition of these roads, it was likely that supply for an overland force was possible.

TSUJI Masanobu

Lieutenant Colonel TSUJI Masanobu arrived in Rabaul from the Philippines on 24 July 1942 along with the staff of 17th Army Headquarters. He had been sent as a representative of Imperial Headquarters to direct operations in Papua. He was originally intended to make a judgement about the overland offensive on Port Moresby based on the report of the Advance Party. TSUJI, however, acting on his own authority, ordered the overland offensive to be conducted without waiting for the feasibility study report. Staff of the 17th Army were advised on 15 July after TSUJI’s arrival in the Philippines.

In order to effectively carry out an air war of attrition against eastern New Guinea, it is imperative that Port Moresby be attacked as soon as possible. Even the Emperor is particularly concerned about this issue. Therefore, without waiting for the results of the Ri-gô study, Imperial GHQ has ordered the 17th Army, by this Great Order, to attack Port Moresby. It is expected that central Army and Navy agreements concerning this will be telegraphed to Rabaul and Davao no later than 24 July. The Ri-gô Operation must now be executed without the feasibility study. I would like the 17th Army to proceed with local agreements with the Navy and begin the offensive against Port Moresby. I would like this achieved at all haste and with firm resolve.

TSUJI’s initiative was not challenged at the time, as many in Imperial Headquarters were leaning towards the idea of the overland offensive, despite the logistical difficulties. Consequently, TSUJI began mobilising for the campaign, specifically by procuring additional supply and engineering units. In order to assess the situation first-hand, and to encourage the commander of the Advance Party whom he had known from Malaya, TSUJI headed for Buna by Navy patrol vessel on 25 July.
Unfortunately, TSUJI was seriously wounded when his vessel came under Allied air attack near the Buna coast several days later, and he was subsequently repatriated to Tokyo.

A career soldier of undoubted ability, TSUJI attracted as many critics as admirers with his fanaticism and zeal. Acclaimed for his role in the brilliant strategies of the Malaya campaigns, he was influential on strategic decisions of the Japanese Army at one time or another in most theatres of war in Asia and the Pacific. TSUJI was implicated in several atrocities against Chinese civilians in Malaya and Singapore, and against Allied POWs in the Philippines and Burma, but escaped from Bangkok at the end of the war, thus denying the Allies the opportunity to prosecute him as a war criminal.

He was elected to the Japanese parliament in 1952 on the popularity of his best-selling accounts of his escape from the Allies and his role in the Malaya campaigns. Always controversial, he disappeared, presumed dead, from Laos in 1961 after a turbulent political career from which the shadow of his military past was never fully erased. He was pronounced dead in 1968.

Source:
Australia-Japan Research Project