The Pacific War, sometimes called the Asia–Pacific War or the Pacific Theater, was the theater of World War II fought between the Empire of Japan and the Allies in East and Southeast Asia, the Pacific and Indian Oceans, and Oceania. It was geographically the largest theater of the war, including the Pacific Ocean theater, the South West Pacific theater, the Second Sino-Japanese War, and the brief Soviet–Japanese War, and included some of the largest naval battles in history. War between the Empire of Japan and the Republic of China had begun in 1937, with hostilities dating back to Japan's invasion of Manchuria in 1931, but the Pacific War is more widely accepted to have begun in 1941, when the United States and United Kingdom were brought into the war.
Japan invaded French Indochina in 1940, and extended its control over the entire territory in July 1941. On 7–8 December 1941, Japan attacked the American naval base at Pearl Harbor in Hawaii; the U.S.-held Philippines, Guam, and Wake Island; and the British colonies of Malaya, Singapore, and Hong Kong – followed by a Japanese declaration of war. The Japanese achieved great success over the next six months, allying with Thailand and capturing the listed territories (except for Hawaii) in addition to Borneo, New Britain, the Dutch East Indies, Burma, the Solomon and Gilbert Islands, and parts of New Guinea. In May 1942, Japanese and Allied aircraft carriers fought at the Battle of the Coral Sea, resulting in the retreat of a Japanese invasion force headed for Port Moresby. In June, Japan both invaded the Aleutian Islands and was defeated at the Battle of Midway, considered a key turning point in the war; the Japanese subsequently experiencing great difficulty replacing their losses in ships and aircraft as the U.S. produced ever increasing numbers of both.
Major Allied offensives in the Pacific began in August 1942 with the Guadalcanal and New Guinea campaigns. These were followed by Operation Cartwheel from June 1943, which neutralized the major Japanese base at Rabaul on New Britain by early 1944. Elsewhere, Allied forces recaptured the Aleutian Islands by August 1943, and initiated the Gilbert and Marshall Islands campaign in November 1943, which lasted until February 1944. In the Battle of the Philippine Sea in June 1944, the Japanese fleet took heavy damage; the Allied campaign to recapture the Philippines began in October and set off the Battle of Leyte Gulf, after which the Japanese were unable to fight further surface engagements and resorted to kamikaze attacks. The rest of the war was characterized by an Allied strategy of island hopping, with invasions of the Mariana and Palau Islands, Iwo Jima, and Okinawa between June 1944 and June 1945. This enabled a blockade of the Japanese home islands and the start of a strategic air raid campaign which caused widespread urban destruction.
In China, Japan made large gains in Operation Ichi-Go between April and December 1944, while in Burma, the Japanese launched an offensive into India which was reversed by July 1944 and led to its liberation by the Allies in May 1945. From the start of the war, the Allies had adopted a "Europe first" stance, giving priority to defeating Germany; after Germany's surrender in May 1945, Allied forces were shifted to the Pacific in anticipation for Operation Downfall, a planned invasion of Japan. This became unnecessary after the U.S. atomic bombings of Hiroshima and Nagasaki on 6 and 9 August 1945 and Soviet invasion of Manchuria on 9 August, after which Japan surrendered unconditionally on 15 August and signed a surrender document on 2 September, ending World War II. Japan lost its former possessions in Asia and the Pacific, and was occupied by the Allies until 1952.
Names of the war
In Allied countries during the war, the "Pacific War" was not usually distinguished from World War II, or was known simply as the War against Japan. In the United States, the term Pacific theater was widely used. The US Armed Forces considered the China Burma India theater to be distinct from the Asiatic-Pacific theater during the conflict.
Japan used the name Greater East Asia War (大東亜戦争, Dai Tō-A Sensō), as chosen by a cabinet decision on 10 December 1941, to refer to both the war with the Western Allies and the ongoing war in China. This name was released to the public on 12 December, with an explanation that it involved Asian nations achieving their independence from the Western powers through armed forces of the Greater East Asia Co-Prosperity Sphere. Japanese officials integrated what they called the Japan–China Incident (日支事変, Nisshi Jihen) into the Greater East Asia War. During the Occupation of Japan (1945–1952), these terms were prohibited in official documents (although their informal usage continued). The war became officially known as the Pacific War (太平洋戦争, Taiheiyō Sensō). The Fifteen Years' War (十五年戦争, Jūgonen Sensō) is also used, referring to the period from the Mukden incident of 1931 through 1945.
Participants
Allies
The major Allied participants included China, the United States, and the British Empire. China had already been engaged in a war against Japan since 1937. The US and its territories, including the Philippine Commonwealth, entered the war after the Japanese attack on Pearl Harbor in 1941, which was followed by declarations of war by Japan on Australia, Canada, New Zealand and the United Kingdom, as well as the Dutch government-in-exile which retained control of the Dutch East Indies. All of these were members of the Pacific War Council. From 1944 the French commando group Corps Léger d'Intervention also took part in resistance operations in Indochina. Some active pro-allied guerrillas in Asia included the Hukbalahap, the Korean Liberation Army, the Free Thai Movement, the Việt Minh, the Khmer Issarak, and the Malayan Peoples' Anti-Japanese Army.
The Soviet Union fought two short, undeclared border conflicts with Japan in 1938 and again in 1939, then remained neutral through the Soviet–Japanese Neutrality Pact of April 1941, until August 1945 when it (and Mongolia) joined the rest of the Allies and invaded the territory of Manchukuo, China, Inner Mongolia, and the Japanese territories such as Korea and South Sakhalin (Karafuto).
Mexico provided air support in the form of the 201st Fighter Squadron and Free France sent naval support in the form of Le Triomphant and later the Richelieu.
The Kingdom of Italy, following the day after the Armistice of Cassibile on 9 September 1943 was involved in multiple military confrontations with Japan in the numerous Italian Concessions in China, and later on, soon after Italy's official declaration of war on Japan on 15 July 1945, sent the Italian destroyer Carabiniere which participated in a total of 38 missions in the Pacific War.
Axis powers and aligned states
The Axis-aligned states which assisted the Empire of Japan included Thailand under a military government of Plaek Phibunsongkhram. Also involved were members of the Greater East Asia Co-Prosperity Sphere, which included the Manchukuo Imperial Army and Collaborationist Chinese Army of the Japanese puppet states of Manchukuo (consisting of most of Manchuria), and the collaborationist Wang Jingwei regime (which controlled the coastal regions of China), respectively.
Japan conscripted many soldiers from its colonies of Korea and Taiwan. Collaborationist security units were also formed in Hong Kong, Singapore, the Philippines, the Dutch East Indies, British Malaya, British Borneo, British Burma, former French Indochina (after the overthrow of the French regime in 1945), as well as Timorese militia. Macau was the only notable unoccupied European colony in the region, but its administrators Gabriel Maurício Teixeira and Pedro José Lobo were forced to accept Japanese demands anyway.
Germany and Italy both had limited involvement in the Pacific War. The German and the Italian navies operated submarines and raiding ships in the Indian and Pacific Oceans, notably the Monsun Gruppe.
Theaters
Between 1942 and 1945, there were four main areas of conflict in the Pacific War: China, the Central Pacific, South-East Asia and the South West Pacific. US sources refer to two theaters within the Pacific War: the Pacific theater and the China Burma India Theater (CBI). However, these were not operational commands.
In the Pacific, the Allies divided operational control of their forces between two supreme commands, known as Pacific Ocean Areas and Southwest Pacific Area.
The Imperial Japanese Navy (IJN) did not integrate its units into permanent theater commands. The Imperial Japanese Army (IJA), which had already created the Kwantung Army to oversee its occupation of Manchukuo and the China Expeditionary Army during the Second Sino-Japanese War, created the Southern Expeditionary Army Group at the outset of its conquests of South East Asia. This headquarters controlled the bulk of the Japanese Army formations which opposed the Western Allies in the Pacific and South East Asia.
Historical background
Conflict between China and Japan
By 1937, Japan controlled Manchuria and was prepared to move deeper into China. The Marco Polo Bridge Incident on 7 July 1937 provoked full-scale war between China and Japan. The Nationalist Party and the Chinese Communists suspended their civil war in order to form a nominal alliance against Japan, and the Soviet Union quickly lent support by providing large amounts of materiel to Chinese troops. In August 1937, Generalissimo Chiang Kai-shek deployed some of his best troops to defend Shanghai against some 300,000 Japanese troops attempting to seize the city, which fell to Japan after three months of fighting. The Japanese continued to push deeper into China, capturing the capital Nanjing in mid-December 1937 and committing atrocities in the Nanjing Massacre, including rape, murder and torture.
In March 1938, Nationalist forces won their first victory at Taierzhuang, but the city of Xuzhou (徐州) was taken by the Japanese in May. In June 1938, Japan deployed about 350,000 troops to invade Wuhan and captured it in October after a four-month campaign. The Japanese achieved major military victories, but world opinion—in particular in the US—was hostile to Japan's invasion, especially after the Panay incident. In addition, the Japanese had failed to destroy the Chinese army, which continued to resist from the new Nationalist capital in Chongqing, or in the case of the Communists, Yan'an.
In 1939, Japanese forces tried to push into the Soviet Far East. They were defeated in the Battle of Khalkhin Gol by a mixed Soviet and Mongolian force led by Georgy Zhukov. This caused the Japanese to abandon attempts to expand to the north, while Soviet aid to China ceased as a result of the Soviet–Japanese Neutrality Pact. In September 1940, Japan decided to invade French Indochina, which was controlled at the time by Vichy France. On 27 September Japan signed a military alliance with Germany and Italy, becoming one of the three main Axis powers.
The war entered a new phase with Japanese defeats at the Battle of Suixian–Zaoyang, the 1st Battle of Changsha, the Battle of Kunlun Pass and the Battle of Zaoyi. After these victories, Chinese nationalist forces launched a large-scale counter-offensive in early 1940; however, due to a lack of military-industrial capacity, they were repulsed in late March 1940. In August 1940, Chinese communists launched an offensive in Central China; in retaliation, Japan instituted the "Three Alls Policy" ("Kill all, Burn all, Loot all") in occupied areas, killing at least 2.7 million civilians.
By 1941 the conflict had become a stalemate. Although Japan had occupied much of northern, central, and coastal China, the Nationalist Government had retreated to the interior and set up a provisional capital at Chongqing, while the Chinese communists remained in control of base areas in Shaanxi. Japanese offensive action against the retreating and regrouping Chinese forces was largely stalled by the mountainous terrain in southwestern China, while the Communists organized widespread guerrilla and saboteur activities in northern and eastern China behind the Japanese front line.
Japan sponsored several puppet governments, one of which was headed by Wang Jingwei. Conflicts between Chinese Communist and Nationalist forces vying for territorial control behind enemy lines culminated in a major armed clash in January 1941, effectively ending their co-operation.
Japanese strategic bombing efforts mostly targeted large Chinese cities such as Shanghai, Wuhan, and Chongqing, with around 5,000 raids from February 1938 to August 1943. Japan's strategic bombing campaigns killed between 260,000 and 350,934 non-combatants.
By the eve of Pearl Harbor, some 7,500,000 Chinese soldiers and civilians had died in the Japanese invasion. Japanese casualties by the end of 1941, per their own records, were some 600,000 including 185,000 killed.
Tensions between Japan and the West
As early as 1935, Japanese military strategists had concluded that the Dutch East Indies were, due to their abundant oil reserves, crucially important for further expansion by the Japanese Empire. By 1940 the Japanese also included Indochina, Malaya, and the Philippines within their concept of the Greater East Asia Co-Prosperity Sphere. Japanese troop build-ups in Hainan, Taiwan, and Haiphong were noted in foreign media, Japanese military officers were increasingly and openly talking about the prospect of war, and Admiral Sankichi Takahashi was reported as stating that a showdown with the US was necessary.
In an effort to discourage Japanese militarism, Western powers including Australia, the US, Britain, and the Dutch government in exile, which controlled the Dutch East Indies, stopped selling oil, iron ore, and steel to Japan. In Japan, the government and Japanese nationalists viewed these embargoes as acts of aggression; imported oil made up about 80% of domestic consumption, without which Japan's economy would grind to a halt. The Japanese media, influenced by military propagandists, began to refer to the embargoes as the "ABCD line" ("American-British-Chinese-Dutch").
Japanese preparations
The Japanese Imperial General Headquarters (GHQ) began planning for a war with the Western powers in April or May 1941. Japan increased its naval budget and placed large formations of the Army, along with their attached air components, under the command of the Imperial Japanese Navy. Historically, the IJA consumed the majority of the state's military budget (with a 73% – 27% split in 1940), but from 1942 to 1945 the IJA would account for 60% of Japan's military spending, while the IJN would account for 40%. Japan's key initial objective was to seize economic resources in the Dutch East Indies and Malaya, in order to alleviate the effects of the Allied embargo. This was known as the Southern Plan. It was decided—because of the close relationship between the UK and the US, and the belief that the US would inevitably become involved in the ongoing war in Europe—that Japan would also seize the Philippines, Wake Island and Guam.