Imperial Japanese Army

The Imperial Japanese Army (Japanese: 大日本帝国陸軍, Hepburn: Dai-Nippon Teikoku Rikugun, "Army of the Greater Japanese Empire") was the official ground-based armed force of the Empire of Japan from 1868 to 1945. It was controlled by the Imperial Japanese Army General Staff Office and the Ministry of the Army, both of which were nominally subordinate to the Emperor of Japan as supreme commander of the army and the Imperial Japanese Navy. Later an Inspectorate General of Aviation became the third agency with oversight of the army. During wartime or national emergencies, the nominal command functions of the emperor would be centralized in an Imperial General Headquarters (IGHQ), an ad-hoc body consisting of the chief and vice chief of the Army General Staff, the Minister of the Army, the chief and vice chief of the Naval General Staff, the Inspector General of Aviation, and the Inspector General of Military Training.

Army
The Army is divided into 12 army groups.
 * Imperial Army (~230,000–250,000 men) – Commanded by Marshal HIH Prince Kan-in-Kotohito
 * General Army (総軍 Sō-gun equivalent to the Army Group or Front) – Commanded by a Marshal or General
 * Area Army (方面軍　Hōmen-gun 1942–1945 equivalent to the Field Army) – Commanded by a General or Lieutenant-General
 * Army (equivalent to the Corps)- Commanded by a Lieutenant-General
 * Division (~20,000 men) – Consisted of 3 infantry regiments, 1 cavalry regiment, 1 artillery regiment, 1 engineering battalion and 1 army service corps. Commanded by a Lieutenant-General.
 * Independent Brigade (~5600 men) – Consisted of 5 battalions, along with other units. Commanded by a Major-General.
 * Regiment (~3,800 men) – Consisted of 3 battalions, each of 1,100 men, along with other units. Commanded by a Colonel.
 * Battalion (~1,100 men) – Consisted of 4 companies, each of 180 men, along with other units. Commanded by a Lieutenant-Colonel.
 * Company (~180 men) – Consisted of 3 platoons, each of 54 men, and a headquarters unit with 19 men. Commanded by a Captain.
 * Platoon (~50 men) – Consisted of 3 sections, each of 15 men. Commanded by a Lieutenant.
 * Section (~12–15 men) – Consisted of 3 teams, each of about 4 men. Led by a Corporal.
 * Team (4 men) – Led by a Senior Private.

General Armies
The General Army (総軍, Sō-gun) was the highest level in the organizational structure of the Imperial Japanese Army. It corresponded to the army group in western military terminology. Intended to be self-sufficient for indefinite periods, the general armies were commanded by either a field marshal or a full general.

The initial General Army was the Japanese Manchurian Army, formed from 1904–1905 during the Russo-Japanese War as a temporary command structure to coordinate the efforts of several Japanese armies in the campaign against Imperial Russia.

In terms of a permanent standing organization, the Japanese Army created the Kantōgun, usually known in English as the Kwantung Army, to manage its overseas deployment in the Kwantung Territory and Manchukuo from 1906.

Subsequent general armies were created in response to the needs of the Second Sino-Japanese War and World War II, in which increased overseas deployment called for an organizational structure that could respond quickly and autonomously from the Imperial Japanese Army General Staff in Tokyo. As a result, Japanese forces were re-organized into three separate overseas operational commands: (Manchuria, China and Southeast Asia), with the Japanese home islands forming a fourth.

Towards the end of World War II, the home island command (i.e. the General Defense Command) was restructured geographically into the First General Army in the east, Second General Army in the west, and the Air General Army in charge of military aviation.

With the official Japanese surrender in September 1945, all of the general armies were dissolved, except for the First General Army, which continued to exist until November 30, 1945, as the 1st Demobilization Headquarters.

Kwantung Army

The Kwantung Army (Japanese: 関東軍, Kantō-gun) was the largest army group of the Imperial Japanese Army from 1919 to 1945. The Kwantung Army was formed in 1906 as a security force for the Kwantung Leased Territory and South Manchurian Railway Zone after the Russo-Japanese War, and was expanded into an army group during the Interwar period to support Japanese interests in China, Manchuria, and Mongolia. The Kwantung Army became the largest and most prestigious command in the Imperial Japanese Army, and many of its personnel were promoted to high positions in the Japanese military and civil government, including Hideki Tōjō and Seishirō Itagaki. The Kwantung Army was largely responsible for the creation of the Japanese puppet state of Manchukuo and was one of the main Japanese fighting forces during the Second Sino-Japanese War from 1937.

In August 1945, the Kwantung Army was engaged by Soviet troops during the Manchurian Strategic Offensive Operation. The Kwantung Army surrendered to the Soviets the day after the Surrender of Japan and was subsequently dissolved. The Kwantung Army was responsible for many of the worst Japanese war crimes during World War II, including the sponsorship of Unit 731 which performed biological warfare and human experimentation on civilians and prisoners of war.

China Expeditionary Army

The China Expeditionary Army (支那派遣軍, Shina hakengun) was an army group of the Imperial Japanese Army from 1939 to 1945. The China Expeditionary Army was established in September 1939 from the merger of the Central China Expeditionary Army and Japanese Northern China Area Army, and was headquartered in the pro-Japanese Reorganized National Government's capital city of Nanking. The China Expeditionary Army was responsible for all Japanese military operations in China and was the main fighting force during the Second Sino-Japanese War, with over 1 million soldiers under its command at its peak. The China Expeditionary Army was dissolved upon the Surrender of Japan in August 1945.

In military literature, the China Expeditionary Army is often referred to by the initials "CEA".

Central China Expeditionary Army

Central China Expeditionary Army (Japanese: 中支那派遣軍, Nakashina hakengun) was a field army of the Imperial Japanese Army during the Second Sino-Japanese War. On November 7, 1937 Japanese Central China Area Army (CCAA) was organized as a reinforcement expeditionary army by combining the Shanghai Expeditionary Army (SEF) and the IJA Tenth Army. General Iwane Matsui was appointed as its commander-in-chief, concurrent with his assignment as commander-in-chief of the SEF. Matsui reported directly to Imperial General Headquarters. After the Battle of Nanjing, the CCAA was disbanded on February 14, 1938 and its component units were reassigned to the Central China Expeditionary Army.

On September 12, 1939 by Army Order 362, the China Expeditionary Army was formed with the merger of the Central China Expeditionary Army with the Northern China Area Army.

Northern China Expeditionary Army

The Japanese North China Area Army (北支那方面軍, Kita Shina hōmen gun) was a field army of the Imperial Japanese Army during the Second Sino-Japanese War.

Southern Expeditionary Army

The Southern Expeditionary Army (南方軍, Nanpō gun) was an army group of the Imperial Japanese Army during World War II. It was responsible for all military operations in South East Asian and South West Pacific campaigns of World War II.[1] Its military symbol was NA. The Southern Expeditionary Army Group was formed on November 6, 1941, under the command of Gensui Count Terauchi Hisaichi, with orders to attack and occupy Allied territories and colonies in South East Asia and the South Pacific.

General Defense Command

The General Defense Command (防衛総司令部, 'Bōei Soshireibu') was a headquarters organization equivalent to an army group within the Imperial Japanese Army established to control all land and air units stationed within Japan proper, Korea and Taiwan during the Pacific War. The General Defense Command was established on July 5, 1941 under the direct command of the Emperor via the Imperial General Headquarters. For administrative, recruiting and accounting purposes, Japan was divided into six army districts, each with a garrison force equivalent to an army corps: The General Defense Command was also responsible for anti-aircraft defenses, and for organizing civil defense training.
 * Eastern District Army – HQ in Tokyo and responsible for the Kantō region and northern Honshū
 * Western District Army – HQ in Fukuoka and responsible for southwestern Honshū, Shikoku and the Ryukyu Islands.
 * Northern District Army – HQ in Sapporo and responsible for Hokkaidō and Karafuto.
 * Central District Army – HQ in Osaka and responsible for central Honshū.
 * Chosen Army – HQ in Keijo and responsible for Korea
 * Taiwan Army – HQ in Taihoku and responsible for Taiwan.

On April 8, 1945, in preparation for Operation Downfall (or Operation Ketsugō (決号作戦, Ketsugō sakusen) in Japanese terminology), the General Defense Command was dissolved, and its duties assumed by the new First General Army and Second General Army.

First General Army

The First General Army (第1総軍 (日本軍), Dai-ichi Sōgun) was an army group of the Imperial Japanese Army responsible for the defense of eastern and northern Honshū, including the Tōkai and Kantō regions during the final stage of the Pacific War.

Second General Army

The Second General Army (第2総軍 (日本軍), Dai-ni Sōgun) was an army group of the Imperial Japanese Army responsible for the defense of western Honshū, Kyūshū and Shikoku during the final stage of the Pacific War.

Air General Army

The Air General Army (航空総軍, Kōkū Sōgun) was a Japanese military unit responsible for the defense of the country against Allied air raids during the last months of World War II. The Air General Army was formed in April 1945 to better coordinate Japan's air defenses in response to the mounting air offensive against Japan and the expected invasion of the country later that year. The army was disbanded following the end of the war.

Area Army
Area Armies (方面軍, Hōmen-gun) in Japanese military terminology were equivalent to field armies in western militaries. Area Armies were normally commanded by a general or lieutenant general. There is much confusion between the similarly numbered Area Armies and Armies in historical records, as many writers often did not make a clear distinction when describing the units involved.

Japanese First Area Army

The Japanese First Area Army (第1方面軍, Dai-ichi hōmen gun) was a field army of the Imperial Japanese Army during World War II, based in northern Manchukuo and active in combat against the Soviet Union in the closing stages of the war.

Japanese Second Area Army

The Japanese Second Area Army (第2方面軍, Dai ni hōmen gun) was a field army of the Imperial Japanese Army during World War II. The Japanese 2nd Area Army was formed on July 4, 1942 under the control of the Kwantung Army as a reserve and garrison force to maintain security and public order in Manchukuo. It was disbanded on June 13, 1945, and its various components were reassigned to other commands.

Japanese Third Area Army

The Japanese Third Area Army (第3方面軍, Dai san hōmen gun) was a field army of the Imperial Japanese Army during World War II, based in southern Manchukuo and active in combat against the Soviet Union in the very final stages of the war.

Japanese Fifth Army

The Japanese Fifth Area Army (第5方面軍, Dai-go hōmen gun) was a field army of the Imperial Japanese Army during the closing stages of World War II. It saw combat against the Soviet Union in Japan’s northern territories.

Japanese Sixth Area Army

The Japanese Sixth Area Army (第6方面軍, Dai roku hōmen gun) was a field army of the Imperial Japanese Army during both the Second Sino-Japanese War and World War II. The Japanese 6th Area Army was formed on August 25, 1944 under the China Expeditionary Army primarily as a military reserve and garrison force for the occupation of the central provinces of China between the Yangtze River and the Yellow River. After the success of Operation Ichi-Go, many veteran units were transferred out of China to fronts in the Pacific War, which left the 6th Area Army to guard gains in central China. The 6th Area Army was demobilized at the surrender of Japan on August 15, 1945 at Hankou (part of modern Wuhan) in China, without having seen significant combat.

Japanese Seventh Army

The Japanese Seventh Area Army (第7方面軍, Dai nana hōmen gun) was a field army of the Imperial Japanese Army formed during final stages of the Pacific War and based in Japanese-occupied Malaya, Singapore and Borneo, Java, and Sumatra.

Japanese Eighth Army

The Japanese Eighth Area Army (第8方面軍, Dai-hachi hōmen gun) was a field army of the Imperial Japanese Army during World War II. The Japanese 8th Area Army was formed on November 16, 1942 under the Southern Expeditionary Army Group for the specific task of opposing landings by Allied forces in Japanese-occupied Solomon Islands and New Guinea.[1] It had its headquarters at Rabaul, New Britain and saw considerable combat in the Solomon Islands campaign, Bougainville campaign and New Guinea campaign.

Japanese Tenth Army

The Japanese Tenth Area Army (第10方面軍, Dai-jū hōmen-gun) was a field army of the Imperial Japanese Army during World War II. The 10th Area Army was originally formed out of the Taiwan Army of Japan on September 29, 1944 under the Imperial General Headquarters as part of the last desperate defense effort by the Empire of Japan to deter possible landings of Allied forces in Taiwan during Operation Downfall (or Operation Ketsugō (決号作戦, Ketsugō sakusen) in Japanese terminology). It was headquartered in Taipei. and consisted of the 32nd army, 40th army, and other smaller units.

As priorities after Battle of Okinawa shifted, the 40th army headquarters were reassigned to control the units being raised in Kagoshima Prefecture, and the former units of 40th army were subordinated directly to the 10th Area Army from 14 May 1945.

As with similar field armies raised on the Japanese home islands during this time, the 10th Area Army consisted mostly of poorly trained reservists, conscripted students and home guard militia. In addition, the Japanese had organized the Patriotic Citizens Fighting Corps — which included all healthy men aged 15–60 and women 17–40 — to perform combat support, and ultimately combat jobs. Weapons, training, and uniforms were generally lacking: some men were armed with nothing better than muzzle-loading muskets, longbows, or bamboo spears; nevertheless, they were expected to make do with what they had.

The 10th Area Army was demobilized at the surrender of Japan on August 15, 1945 without having seen combat in Taiwan, although units transferred to the Ryukyu islands for the Battle of Okinawa were annihilated by American forces.

Japanese Eleventh Area Army

The Japanese Eleventh Area Army (第11方面軍, Dai jyūichi hōmen gun) was a field army of the Imperial Japanese Army during World War II. The Japanese 11th Area Army was formed on February 6, 1945 under the Imperial General Headquarters and transferred to the control of the Japanese First General Army on April 8, 1945. It was part of the last desperate defense effort by the Empire of Japan to deter possible landings of Allied forces in central Honshū during Operation Downfall (or Operation Ketsugō (決号作戦, Ketsugō sakusen) in Japanese terminology). The Japanese 11th Area Army was responsible for the Tōhoku region of Japan and was headquartered in Sendai, Miyagi.

It consisted mostly of poorly trained reservists, conscripted students and home guard militia. In addition, the Japanese had organized the Volunteer Fighting Corps — which included all healthy men aged 15 to 60 and women 17 to 40 — to perform combat support, and ultimately combat jobs. Weapons, training, and uniforms were generally lacking: some men were armed with nothing better than muzzle-loading muskets, longbows, or bamboo spears; nevertheless, they were expected to make do with what they had.

The 11th Area Army was demobilized at the surrender of Japan on August 15, 1945 without having seen combat.

Japanese Twelfth Area Army

The Japanese Twelfth Area Army (第12方面軍, Dai-jūni hōmen gun) was a field army of the Imperial Japanese Army during World War II. The Japanese 12th Area Army was formed on February 2, 1945 under the First General Army as part of the last desperate defense effort by the Empire of Japan to deter possible landings of Allied forces in central Honshū during Operation Downfall (or Operation Ketsugō (決号作戦, Ketsugō sakusen) in Japanese terminology). The Japanese 12th Area Army was responsible for the Kantō region of Japan and was headquartered in Tokyo.

It consisted mostly of poorly trained reservists, conscripted students and home guard militia. In addition, the Japanese had organized the Volunteer Fighting Corps — which included all healthy men aged 15–60 and women 17–40 — to perform combat support, and ultimately combat jobs. Weapons, training, and uniforms were generally lacking: some men were armed with nothing better than muzzle-loading muskets, longbows, or bamboo spears; nevertheless, they were expected to make do with what they had.

The 12th Area Army was demobilized at the surrender of Japan on September 2, 1945 without having seen combat.

Japanese Thirteenth Area Army

The Japanese Thirteenth Area Army (第13方面軍, Dai-jyūhachi hōmen gun) was a field army of the Imperial Japanese Army during the final stages of World War II. The Japanese 13th Area Army was formed on 1945-02-01 under the Japanese First General Army as part of the last desperate defense effort by the Empire of Japan to deter possible landings of Allied forces in central Honshū during Operation Downfall (or Operation Ketsugō (決号作戦, Ketsugō sakusen) in Japanese terminology). The Japanese 13th Area Army was responsible for the Tōkai region of Japan and was headquartered in Nagoya.

It consisted mostly of poorly trained reservists, conscripted students and home guard militia. In addition, the Japanese had organized the Patriotic Citizens Fighting Corps — which included all healthy men aged 15–60 and women 17–40 — to perform combat support, and ultimately combat jobs. Weapons, training, and uniforms were generally lacking: some men were armed with nothing better than muzzle-loading muskets, longbows, or bamboo spears; nevertheless, they were expected to make do with what they had.

The 13th Area Army was demobilized at the surrender of Japan on August 15, 1945 without having seen combat.

Japanese Fourteenth Area Army

The Fourteenth Area Army (第14方面軍, Dai-jyūyon hōmen gun) was a field army of the Imperial Japanese Army (IJA) during World War II. It was formed in the Philippines on July 28, 1944, when Allied landings were considered imminent. The Fourteenth Area Army was formed by reinforcing and renaming the Japanese Fourteenth Army (第14軍, Dai-jyūyon gun). (An IJA "area army" was equivalent to a field army in other militaries, while an IJA "army" was a smaller, corps-level formation.)

Navy
The Imperial Japanese Navy was the third largest navy in the world by 1920, behind the Royal Navy and the United States Navy (USN).[2] It was supported by the Imperial Japanese Navy Air Service for aircraft and airstrike operation from the fleet. It was the primary opponent of the Western Allies in the Pacific War.

The origins of the Imperial Japanese Navy go back to early interactions with nations on the Asian continent, beginning in the early medieval period and reaching a peak of activity during the 16th and 17th centuries at a time of cultural exchange with European powers during the Age of Discovery. After two centuries of stagnation during the country's ensuing seclusion policy under the shōgun of the Edo period, Japan's navy was comparatively backward when the country was forced open to trade by American intervention in 1854. This eventually led to the Meiji Restoration. Accompanying the re-ascendance of the Emperor came a period of frantic modernization and industrialization. The navy had several successes, sometimes against much more powerful enemies such as in the Sino-Japanese War and the Russo-Japanese War, before being largely destroyed in World War II.

Army Air Force
The Imperial Japanese Army Air Service or Imperial Japanese Army Air Force (IJAAS or IJAAF) (大日本帝國陸軍航空部隊, Dainippon Teikoku Rikugun Kōkūbutai) or, more literally, the Greater Japan Empire Army Air Corps, was the aviation force of the Imperial Japanese Army (IJA). Just as the IJA in general was modeled mainly on the German Army, the IJAAS initially developed along similar lines to the Imperial German Army Aviation; its primary mission was to provide tactical close air support for ground forces, as well as a limited air interdiction capability. The IJAAS also provided aerial reconnaissance to other branches of the IJA. While the IJAAS engaged in strategic bombing of cities such as Shanghai, Nanking, Canton, Chongqing, Rangoon, and Mandalay, this was not the primary mission of the IJAAS, and it lacked a heavy bomber force.

It did not usually control artillery spotter/observer aircraft; artillery battalions controlled the light aircraft and balloons that operated in these roles.

Navy Air Force
The Imperial Japanese Navy Air Service (大日本帝國海軍航空隊, Dai-Nippon Teikoku Kaigun Kōkū-tai) was the air arm of the Imperial Japanese Navy (IJN). The organization was responsible for the operation of naval aircraft and the conduct of aerial warfare in the Pacific War.

The Japanese military acquired their first aircraft in 1910 and followed the development of air combat during World War I with great interest. They initially procured European aircraft but quickly built their own and launched themselves onto an ambitious aircraft carrier building program. They launched the world's first purpose-built aircraft carrier, Hōshō, in 1922. Afterwards they embarked on a conversion program of several excess battlecruisers and battleships into aircraft carriers. The IJN Air Service had the mission of national air defence, deep strike, naval warfare, and so forth. It retained this mission to the end.

The Japanese pilot training program was very selective and rigorous, producing a high-quality and long-serving pilot corps, who were very successful in the air during the early part of World War II in the Pacific. However, the long duration of the training program, combined with a shortage of gasoline for training, did not allow the IJN to rapidly provide qualified replacements in sufficient numbers. Moreover, Japan, unlike the U.S. or Britain, never altered its program to speed up the training process of its recruits. The resultant decrease in quantity and quality, among other factors, resulted in increasing casualties toward the end of the war.

Japanese navy aviators, like their army counterparts, preferred maneuverable aircraft, leading to lightly built but extraordinarily agile types, most famously the A6M Zero, which achieved its feats by sacrificing armor and self-sealing fuel tanks. Aircraft with armor and self-sealing fuel tanks, such as the Kawanishi N1K-J would not enter service until late 1944–1945, which was too late to have a meaningful impact. The Imperial Japanese Navy Air Service was equal in function to the Royal Navy's Fleet Air Arm (FAA).

Corps
The Japanese Army (軍, gun) corresponded to an army corps in American or British military terminology. It was usually commanded by a lieutenant general.
 * First Army – China
 * Second Army – China
 * Third Army – Manchukuo
 * Fourth Army – Manchukuo
 * Fifth Army – Manchukuo
 * Sixth Army – Manchukuo
 * Tenth Army – China
 * Eleventh Army – China
 * Twelfth Army – China
 * Thirteenth Army – China
 * Fourteenth Army – Philippines
 * Fifteenth Army – Burma
 * Sixteenth Army – Java
 * Seventeenth Army – Solomon Islands
 * Eighteenth Army – New Guinea
 * Nineteenth Army – eastern Netherlands East Indies
 * Twentieth Army – China
 * Twenty-First Army – China
 * Twenty-Second Army – China
 * Twenty-Third Army – China
 * Twenty-Fifth Army – Malaya, Singapore, Sumatra
 * Twenty-Seventh Army – Chishima Islands
 * Twenty-Eighth Army – Burma
 * Twenty-Ninth Army – British Malaya
 * Thirtieth Army – Manchukuo
 * Thirty-First Army – Truk
 * Thirty-Second Army – Okinawa
 * Thirty-Third Army – Burma
 * Thirty-Fourth Army – Manchukuo
 * Thirty-Fifth Army – Philippines
 * Thirty-Sixth Army – Japanese home islands
 * Thirty-Seventh Army – Borneo
 * Thirty-Eighth Army -Indochina
 * Thirty-Ninth Army -Thailand
 * Fortieth Army – Japanese home islands
 * Forty-First Army – Philippines
 * Forty-Third Army – China
 * Forty-Fourth Army – Manchukuo
 * Fiftieth Army – Japanese home islands
 * Fifty-First Army – Japanese home islands
 * Fifty-Second Army – Japanese home islands
 * Fifty-Third Army – Japanese home islands
 * Fifty-Fourth Army – Japanese home islands
 * Fifty-Fifth Army – Japanese home islands
 * Fifty-Sixth Army – Japanese home islands
 * Fifty-Seventh Army – Japanese home islands
 * Fifty-Eighth Army – Korea
 * Fifty-Ninth Army – Japanese home islands
 * China Garrison Army – China
 * Mongolia Garrison Army- Inner Mongolia
 * Army of Tokyo Bay
 * Tokyo defense Army


 * Imperial Japanese Army Air Force
 * First Air Army – HQ Tokyo, basing in the Kanto Plain covering the Japanese home islands, Taiwan, Korea and Karafuto.
 * Second Air Army – HQ Hsinking, covering Manchukuo
 * Third Air Army – HQ Singapore, covering Southeast Asia
 * Fourth Air Army – HQ Rabaul, covering the Solomon Islands and New Guinea
 * Fifth Air Army – HQ Nanking, covering Japanese-occupied portions of southern and eastern China.
 * Sixth Air Army – HQ Kyūshū covering Taiwan and Okinawa

Auxiliaries

 * Manchukuo Imperial Army
 * Mengjiang National Army
 * Indian National Army
 * Burmese National Army
 * Kempeitai
 * Japanese Korean Army