The Pacific War lasted from 1941 to 1945, with the Empire of Japan fighting against the United States, the British Empire and their allies. Most of the campaign was fought on a variety of small islands in the Pacific region. Ground fighting in the Pacific was characterized by its intense ferocity, and combat conditions were marked by illness and logistical difficulties, especially for Japanese soldiers. The Imperial Japanese Army (IJA) typically fought alone in these engagements, often with very little naval or aerial support, and the IJA quickly garnered a reputation for tenacious resistance as well as brutality.
At the beginning of the Pacific War in 1941, the Imperial Japanese Army contained 51 divisions, 27 of which were stationed in China. A further 13 divisions defended the Manchurian–Soviet border, due to concerns about a possible attack by the Soviet Union. From 1942 onwards, troops were sent to Hong Kong (23rd Army), the Philippines (14th Army), Thailand (15th Army), Burma (15th Army), the Dutch East Indies (16th Army), and Malaya (25th Army). A total of 5.473 million men served in the Imperial Japanese Army over the course of the war.
Japanese troops suffered from a shortage of supplies, especially food, medicine, munitions, and armaments, largely due to the crippling losses inflicted on Japan's merchant fleet by Allied submarines. Logistical issues were worsened by a longstanding rivalry with the Imperial Japanese Navy, with army and navy planners generally viewing support for the other as transactional instead of collaborative. As many as two-thirds of Japan's total military deaths were a result of illness or starvation.
First offensive maneuvers (1941–1942) Once the Pacific War began, the Imperial Japanese Army quickly captured many critical areas across the Pacific. These included British Malaya, Guam, the Philippines and Wake Island. A combination of Japanese naval supremacy, the Allied doctrine of"Europe first", and poor Allied defensive preparations meant the Japanese encountered relatively little opposition during this stage of the war. About 85% of American resources, including 68% of US Army personnel, went towards the European Theater in early 1942. The Japanese control of large parts of Oceania and Asia afforded them the strategic initiative, as these territories were rich in resources critical to the Japanese war economy, including rubber, tin, bauxite and oil. Japan lacked domestic oil reserves, but in 1942 the Dutch East Indies was the fourth largest global producer of oil.
Loss of momentum (1942-1943) Throughout late 1942 and early 1943, the Japanese offensive in New Guinea lost momentum during engagements with Australian and US forces at Milne Bay, along the Kokoda Track and around Buna–Gona. The most significant setback for the Imperial Japanese Army was the months-long Battle of Guadalcanal, a battle of attrition in which the Japanese lost over 25,000 men before abandoning the island in early 1943. Guadalcanal subsequently became one of the largest Allied naval and air bases in the south Pacific. The battle was the first major Allied victory on land in the Pacific Theater, and Guadalcanal would later be used as a staging ground for Allied attacks on the Palau Islands, Bougainville, and Guam.
After the defeat at Guadalcanal, the Japanese were largely forced onto the defensive. Throughout 1943, American forces engaged in an island hopping campaign against Japanese garrisons in the Pacific, adopted a strategy of unrestricted submarine warfare against the Japanese merchant fleet, and began to launch air raids on Japan that gradually destroyed Japan's war economy. Japan's industrial capacity was equivalent to only 10% of that of the United States. Japanese Vice Admiral Raizō Tanaka remarked, "There is no question that Japan's doom was sealed with the closing of the struggle for Guadalcanal."
During the island hopping campaign, American forces captured islands that were deemed strategically essential, and blockade those deemed unimportant, preventing Japanese troops from being resupplied or reinforced. A notable Japanese garrison that was "bypassed" by Allied forces was based on New Britain, where 69,000 Japanese soldiers and 20,000 civilian workers were trapped around Rabaul from late 1943 until the end of the war. The effectiveness of the island hopping strategy came from the fact that it generated significant results despite the limited Allied resources allocated to the Pacific theater, and that the Japanese were largely unable to reinforce isolated island strongholds. Most Japanese-held islands were garrisoned by less than a single division, because so many Japanese troops were dedicated to the China Burma India Theater.
As such, the Allies were able to quickly acquire naval and aerial supremacy over islands they chose to attack. During 1943 and early 1944, many Japanese island garrisons were overcome in less than a week of ground fighting. However, towards the end of the war, the Japanese defense of their island garrisons became more protracted, such as on Iwo Jima and Okinawa, two islands close to the Japanese mainland. The Battle of Peleliu in September 1944 had the highest casualty rate of any American amphibious invasion (40%), but American forces were still able to secure the island after several months. After the capture of Okinawa, Allied strategists planned an invasion of the Japanese mainland, codenamed Operation Downfall, the first stage of which would have been the invasion of Kyūshū island in November 1945.
In Manchuria, despite the impending catastrophe facing Japan on all fronts by mid-1944, the Kwantung Army commander, General Yamada, as well as his top leadership, continued to live "in a fool's paradise." Many of the elite Kwantung Army units had been sent to other theaters by 1945, hollowing out the combat effectiveness of Japanese forces in Manchuria. Even after the atomic bombing of Hiroshima on 6 August, there was no sense of crisis, and special war games (expected to last for five days and attended by a number of high-ranking officers) were conducted near the Soviet border, with Yamada flying to Dairen to dedicate a shrine. The Kwantung Army was taken by complete surprise when the Soviets launched their general offensive at midnight on August 8/9 1945, and swiftly overrun.
The Japanese offered vicious resistance to the Soviet advance when they were able to stand and fight, such as at Mutanchiang, Karafuto, and Shumshu but almost without exception they were overwhelmed and pushed back from the front. After just about a week of combat, reacting to the Soviet declaration of war and the second nuclear strike on Nagasaki, Hirohito overrode his military and ordered the surrender of Japan to the Allies in accordance with the Potsdam Declaration. After some clarifications and a second Imperial rescript reaffirming Japan's surrender, General Yamada and his staff abandoned a plan to withdraw to Tonghua, even though his command was still mostly intact.
The Kwantung Army officially laid down its arms on 17 August 1945, with some sporadic clashes persisting until the end of the month. By the end of the war the IJA had about 664,000 men in Manchuria and 294,200 in Korea.Australian War Memorial: Dispositions and Deaths Retrieved 21 March 2017 The USMC Official History noted that "Although the Kwantung Army reeled back from Soviet blows, most of its units were still intact and it was hardly ready to be counted out of the fight. The emperor's Imperial Rescript ordering Japanese troops to lay down their arms was the only thing which prevented a protracted and costly battle." The final casualties on both sides numbered 12,031 killed and 24,425 wounded for the Soviets and 21,389 killed and about 20,000 wounded for the Japanese. In the end, as Foreign Minister Shigemitsu signed the unconditional surrender of Japan aboard USS Missouri in Tokyo Bay, the men of the vaunted Kantogun, having once dreamed of driving into Siberia as conquerors, instead found themselves transported there as prisoners of war.
Overarching goals
Japanese grand strategy involved expanding its borders and acquiring strategic war materials to offset Japan's lack of economic self-sufficiency, which was exacerbated by its lack of natural resources. Similar to the Nazi German concept of Lebensraum, the Japanese perceived the conquest of Asia and Oceania as a preordained, quasi-divine right. Japanese expansion was also motivated by Pan-Asianism, and a desire to remove American and European influence from the continent.
Furthermore, in response to the Great Depression, the United States passed the Smoot–Hawley Tariff Act, greatly increasing the price of exports, which Japan was reliant on. This furthered the Japanese idea that they needed to be able to survive economically without the help of other nations, prompting the invasion of Manchuria in 1931.
After the Attack on Pearl Harbor and the invasion of Malaya in December 1941, the Empire of Japan was officially at war with the United States and the British Empire. Japan recognized that it would not be able to win a protracted war with the Allied Powers, and Japanese strategists believed that such operations should take no longer than 150 days. They were expecting that Germany would be able to force a British surrender, and subsequently, the United States would be compelled to end the war on terms agreeable to Japanese interests.
Leadership, Control, Organization The official commander-in-chief of the Japanese army was the emperor. He determined its structure, declared war, made peace and concluded treaties. He was supported by two military councils: The Council of Marshals and Admirals (jap. , ) and the Supreme Military Council. (jap. , ) In times of war or serious emergencies, an imperial high command was established under the supervision of the emperor to support him in the exercise of his office. Subordinate to the emperor and the Imperial high command, the Imperial Japanese Army was managed by four main bodies. These were the General Staff, the War Ministry, the General Inspectorate of Military Training and the Inspectorate General of Aviation.
The General Staff (jap. ) comprised the five offices of General Affairs, Operations, Intelligence, Transportation and History. This body was in charge of drafting war plans, training and deploying the combined forces, directing major maneuvers, deploying troops, drafting field regulations, maps and military history, and supervising the General Staff School and the Land Survey Department. The Chief of the General Staff was appointed by the Emperor.
The Ministry of the Army (jap. ) was the administrative, supply and mobilization authority of the army. Its head, the Minister of War, was a member of the cabinet and the liaison between the army and parliament. He had to be a general or lieutenant general, and was directly subordinate to the emperor. The ministry was divided into a secretariat and eight offices. The General Inspectorate of Military Training consisted of an Office for General Affairs and several inspectorates. It was responsible for the technical and tactical training of the individual branches of the armed forces, with the exception of the Army Air Force and other services that were not subordinate to the ministry.
The General Aviation Inspectorate (jap. ) was created by decree on December 7, 1938, to oversee the training of the aviation corps. It comprised a general affairs department and a training department and was headed by a general or lieutenant general. Only in matters of aviation training was it directly subordinate to the Kaiser; otherwise the Inspector General of Aviation was subordinate to the Chief of the General Staff, the Minister of War and the Inspector General of Military Training.
Army organization