Japanese Imperial Army
WAR IN THE PACIFIC
Rise of militarism
In the 1920s the Imperial Japanese Army expanded rapidly and by 1927 had a force of 300,000 men. Unlike western countries, the Army enjoyed a great deal of independence from government. Under the provisions of the Meiji Constitution, the War Minister was held accountable only to the Emperor (Hirohito) himself, and not to the elected civilian government. In fact, Japanese civilian administrations needed the support of the Army in order to survive. The Army controlled the appointment of the War Minister, and in 1936 a law was passed that stipulated that only an active duty general or lieutenant-general could hold the post. As a result, military spending as a proportion of the national budget rose disproportionately in the 1920s and 1930s, and various factions within the military exerted disproportionate influence on Japanese foreign policy.
The Imperial Japanese Army was originally known simply as the Army (rikugun) but after 1928, as part of the Army's turn toward romantic nationalism and also in the service of its political ambitions, it retitled itself the Imperial Army (kōgun).
n 1941, the Imperial Japanese Army had 51 divisions and various special-purpose artillery, cavalry, anti-aircraft, and armored units with a total of 1,700,000 men. At the beginning of the Second World War, most of the Japanese Army (27 divisions) was stationed in China. A further 13 divisions defended the Mongolian border, due to concerns about a possible attack by the Soviet Union. From 1942, soldiers were sent to Hong Kong (23rd Army), the Philippines (14th Army), Thailand (15th Army), Burma (15th Army), Dutch East Indies (16th Army), and Malaya (25th Army). By 1945, there were 5.5 million men in the Imperial Japanese Army.
The New Guinea campaign of the Pacific War lasted from January 1942 until the end of the war in August 1945. During the initial phase in early 1942, the Empire of Japan invaded the Australian-administered territories of the New Guinea Mandate (23 January) and Papua (8 March) and overran western New Guinea (beginning 29/30 March), which was a part of the Netherlands East Indies. During the second phase, lasting from late 1942 until the Japanese surrender, the Allies—consisting primarily of Australian and US forces—cleared the Japanese first from Papua, then the Mandate and finally from the Dutch colony.
The campaign resulted in a crushing defeat and heavy losses for the Empire of Japan. As in most Pacific War campaigns, disease and starvation claimed more Japanese lives than enemy action. Most Japanese troops never even came into contact with Allied forces, and were instead simply cut off and subjected to an effective blockade by the US Navy. Garrisons were effectively besieged and denied shipments of food and medical supplies, and as a result, some claim that 97% of Japanese deaths in this campaign were from non-combat causes.
According to John Laffin, the campaign "was arguably the most arduous fought by any Allied troops during World War II".
Crossing the Owen Stanleys
Buna was easily taken as the Allies had no military presence there (MacArthur wisely chose not to attempt an occupation by paratroopers since any such force would have been easily wiped out by the Japanese). The Japanese occupied the village with an initial force of 1,500 on 21 July and by 22 August had 11,430 men under arms at Buna. Then began the grueling Kokoda Track campaign, a brutal experience for both the Japanese and Australian troops involved. On 17 September, the Japanese had reached the village of Ioribaiwa, just 30 kilometres (20 mi) from the Allied airdrome at Port Moresby. The Australians held firm and began their counterdrive on 26 September. "...the Japanese retreat down the Kokoda Trail had turned into a rout. Thousands perished from starvation and disease; the commanding general, Horii, was drowned." Thus was the overland threat to Port Moresby permanently removed.
Since Port Moresby was the only port supporting operations in Papua, its defence was critical to the campaign. The air defences consisted of P-39 and P-40 fighters. RAAF radar could not provide sufficient warning of Japanese attacks, so reliance was placed on coastwatchers and spotters in the hills until an American radar unit arrived in September with better equipment. Japanese bombers were often escorted by fighters which came in at 30,000 ft (9,100 m)—too high to be intercepted by the P-39s and P-40s—giving the Japanese an altitude advantage in air combat. The cost to the Allied fighters was high. By June, 20–25 P-39s had been lost in air combat, while three more had been destroyed on the ground and eight had been destroyed in landings by accident. The Australian and American anti-aircraft gunners of the Composite Anti-Aircraft Defences played a crucial part. The gunners got a lot of practice; Port Moresby suffered its 78th raid on 17 August 1942. A gradual improvement in their numbers and skill forced the Japanese bombers up to higher altitude, where they were less accurate, and then, in August, to raiding by night.
Although RAAF PBY Catalinas and Lockheed Hudsons were based at Port Moresby, because of the Japanese air attacks, long-range bombers like B-17s, B-25s, and B-26s could not be safely based there and were instead staged through from bases in Australia. This resulted in considerable fatigue for the air crews. Due to USAAF doctrine and a lack of long-range escorts, long-range bomber raids on targets like Rabaul went in unescorted and suffered heavy losses, prompting severe criticism of Lieutenant General George Brett by war correspondents for misusing his forces. But fighters did provide cover for the transports, and for bombers when their targets were within range. Aircraft based at Port Moresby and Milne Bay fought to prevent the Japanese from basing aircraft at Buna, and attempted to prevent the Japanese reinforcement of the Buna area. As the Japanese ground forces pressed toward Port Moresby, the Allied Air Forces struck supply points along the Kokoda Track. Japanese makeshift bridges were attacked by P-40s with 500 lb (230 kg) bombs.
Papua New Guinea, the Bismarcks and the Northern Solomons
The struggle for New Guinea began with the capture by the Japanese of the city of Rabaul at the northeastern tip of New Britain Island in January 1942 (the Allies responded with multiple bombing raids, of which the Action off Bougainville was one). Rabaul overlooks Simpson Harbor, a considerable natural anchorage, and was ideal for the construction of airfields. Over the next year, the Japanese built up the area into a major air and naval base.
The Japanese 8th Area Army (equivalent to a Euroamerican army), under General Hitoshi Imamura at Rabaul, was responsible for both the New Guinea and Solomon Islands campaigns. The Japanese 18th Army (equivalent to a Euroamerican corps), under Lieutenant General Hatazō Adachi, was responsible for Japanese operations on mainland New Guinea.
The colonial capital of Port Moresby on the south coast of Papua was the strategic key for the Japanese in this area of operations. Capturing it would both neutralize the Allies' principal forward base and serve as a springboard for a possible invasion of Australia. For the same reasons, General Douglas MacArthur, Supreme Commander Allied Forces South West Pacific Area was determined to hold it. MacArthur was further determined to conquer all of New Guinea in his progress toward the eventual recapture of the Philippines. General Headquarters Southwest Pacific Area Operational Instruction No.7 of 25 May 1942, issued by Commander-Allied-Forces, General Douglas MacArthur, placed all Australian and US Army, Air Force and Navy Forces in the Port Moresby Area under the control of New Guinea Force.
Japanese seizure of Lae and Salamaua
Due north of Port Moresby, on the northeast coast of Papua, are Huon Gulf and the Huon Peninsula. The Japanese entered Lae and Salamaua, two locations on Huon Gulf, unopposed in early March 1942. MacArthur would have liked to deny this area to the Japanese, but he had neither sufficient air nor naval forces to undertake a counterlanding. The Japanese at Rabaul and other bases on New Britain would have easily overwhelmed any such effort (by mid-September, MacArthur's entire naval force under Vice Admiral Arthur S. Carpender consisted entirely of 5 cruisers, 8 destroyers, 20 submarines 7 small craft). The only Allied response was a bombing raid of Lae and Salamaua by aircraft flying over the Owen Stanley Range from the carriers USS Lexington and USS Yorktown, leading the Japanese to reinforce these sites.
Japanese attempt on Port Moresby
Operation Mo was the designation given by the Japanese to their initial plan to take possession of Port Moresby. Their operation plan decreed a five-pronged attack: one task force to establish a seaplane base at Tulagi in the lower Solomons, one to establish a seaplane base in the Louisiade Archipelago off the eastern tip of New Guinea, one of transports to land troops near Port Moresby, one with a light carrier to cover the landing, and one with two fleet carriers to sink the Allied forces sent in response. In the resulting 4–8 May 1942 Battle of the Coral Sea, the Allies suffered higher losses in ships, but achieved a crucial strategic victory by turning the Japanese landing force back, thereby removing the threat to Port Moresby, at least for the time being.
After this failure, the Japanese decided on a longer term, two-pronged assault for their next attempt on Port Moresby. Forward positions would first be established at Milne Bay, located in the forked eastern end of the Papuan peninsula, and at Buna, a village on the northeast coast of Papua about halfway between Huon Gulf and Milne Bay. Simultaneous operations from these two locations, one amphibious and one overland, would converge on the target city.