Japanese Expansion November 1941 to June 1942

Japanese Expansion November 1941 to June 1942

Japanese Expansion November 1941 to June 1942


The Pacific War component of the Second World War was part of the larger effort at imperial expansion by the Japanese and was the culmination of the colonial rivalry among Japan, Russia, the United States, and various European powers for control of the Pacific Oceans and islands therein. It is one of the numerous conflicts into which World War II is divided, and it was most closely related to the Japanese war efforts in eastern and southern Asia. The Pacific War constituted the largest geographic theater of World War II, being fought in the Pacific and the Indian Oceans and known as the Pacific War.


Learning Objectives 

  • Discuss the significance of Pearl Harbor and the early campaigns in the Pacific theater and connect the battles for Okinawa and Iwo Jima with the greater American “island hopping” strategy.


Key Terms / Key Concepts

Pacific Theater: a major theater of the war between the Allies and Japan defined by the Allied powers’ Pacific Ocean Area command 

Greater East Asia Co-Prosperity Sphere: an imperialist propaganda concept created by the Japanese government to disguise and/or rationalize Japanese conquest of the Pacific and portions of Asia

Pearl Harbor: site of main U.S. military complex in Hawaii, and target of Japanese attack on 7 December 1941, as part of larger Japanese offensive to take control of the Pacific Ocean


Background  of the Pacific War 


The Second Sino-Japanese War between the Empire of Japan and China had been in progress since 7 July 1937, with hostilities dating back as far as 19 September 1931 when the Japanese invaded Manchuria. However, it is more widely accepted that the Pacific War itself began on 7 December (8 December Japanese time) 1941, when the Japanese initiated their offensive against Thailand; the British colonies of Malaya, Singapore, and Hong Kong; and United States military and naval bases in Hawaii, Wake Island, Guam, and the Philippines. 


Summary of the Pacific War


The Pacific War saw the Allies pitted against Japan, the latter aided by Thailand and to a lesser extent by the Axis powers: Germany and Italy. This conflict was marked by naval battles across the Pacific and land campaigns on numerous Pacific islands. The war culminated in massive Allied air raids over Japan, and the atomic bombings of Hiroshima and Nagasaki, accompanied by the Soviet Union's declaration of war and invasion of Manchuria and other territories on 9 August 1945, causing the Japanese to announce an intent to surrender on 15 August 1945. The formal surrender of Japan ceremony took place aboard the battleship USS Missouri in Tokyo Bay on 2 September 1945. After the war, Japan lost all rights and titles to its former possessions in Asia and the Pacific, and its sovereignty was limited to the four main home islands and other minor islands as determined by the Allies. Japan's Shinto Emperor relinquished much of his authority and his divine status through the Shinto Directive in order to pave the way for extensive cultural and political reforms. 


Black and white photo
The Pacific War Council as photographed on 12 October 1942.
Pictured are representatives from the United States (seated),
Australia, Canada, New Zealand, the United Kingdom, China,
the Netherlands, and the Philippine Commonwealth 


Names for the War


Naming this war has been a challenge because of how it overlaps with World War II conflicts in Asia. In Allied countries during the war, the "Pacific War" was not usually distinguished from World War II in general; it was simply known as the War against Japan. In the United States, the term Pacific Theater was widely used, although this was a misnomer in relation to the Allied campaign in Burma, the war in China, and other activities within the South-East Asian Theater. However, 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, 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 into the Greater East Asia War. 

During the Allied military occupation of Japan (1945 – 52), these Japanese terms were prohibited in official documents, although their informal usage continued. The conflict eventually became officially known as the Pacific War. In Japan, the term Fifteen Years' War is also used, to refer to all the fighting in which Japanese forces participated from the Mukden Incident of 1931 through 1945. 




Political map of the Asia-Pacific region, 1939 


The major Allied participants were China, the United States, and the British Empire, but other nations assisted these allies in some fashion. China had already been engaged in a war against Japan since 1937. The United States and its territories, including the Philippine Commonwealth, entered the war after being attacked by Japan. The British Empire was also a major belligerent consisting of British troops along with large numbers of colonial troops from the armed forces of India, Burma, Malaya, Fiji, Tonga, in addition to troops from Australia, New Zealand, and Canada. The Dutch government-in-exile (as possessor of the Dutch East Indies) also participated. All of these were members of the Pacific War Council. Mexico provided some air support, and Free France sent the naval vessels Le Triomphant and the Richelieu. From 1944 the French commando group Corps Léger d'Intervention also took part in resistance operations in Indochina. French Indochinese forces faced Japanese forces in a coup in 1945. The commando corps continued to operate after the coup until liberation. Some active pro-allied guerrillas in Asia included the Malayan Peoples' Anti-Japanese Army, the Korean Liberation Army, the Free Thai Movement, the Việt Minh, and the Hukbalahap.

The Soviet Union fought two brief, undeclared border conflicts with Japan in 1938 and 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, the Japanese protectorate of Korea, as well as Japanese-claimed territory such as South Sakhalin. 


Axis Powers and Aligned States


The Axis-aligned states which assisted Japan included the authoritarian government of Thailand, which formed a cautious alliance with the Japanese in 1941, when Japanese forces issued the government with an ultimatum following the Japanese invasion of Thailand. 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). In the Burma campaign, the anti-British Indian National Army of Free India and the Burma National Army of the State of Burma, among others, were active and fighting alongside their Japanese allies.

Other units assisted the Japanese war effort in their respective territories. Japan conscripted many soldiers from its colonies of Korea and Taiwan. Collaborationist security units were also formed in Hong Kong (reformed ex-colonial police), Singapore, the Philippines (also a member of the Greater East Asia Co-Prosperity Sphere), the Dutch East Indies (the PETA), British Malaya, British Borneo, former French Indochina (after the overthrow of the French regime in 1945) (the Vichy French had previously allowed the Japanese to use bases in French Indochina beginning in 1941, following an invasion) as well as Timorese militia.

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. The Italians had access to concession territory naval bases in China, which was later ceded to collaborationist China by the Italian Social Republic in late 1943. After Japan's attack on Pearl Harbor and the subsequent declarations of war, both navies had access to Japanese naval facilities. 




Between 1942 and 1945, the Allies and Japan divided the Pacific War into several areas of conflict, including the central Pacific, the south Pacific, and the southwest Pacific. These areas overlapped with the China-Burma-India Theater—the Allies name for the area of fighting against the Japanese across south and east Asia. In the Pacific, the Allies divided operational control of their forces between two supreme commands, known as Pacific Ocean Areas and Southwest Pacific Area. In 1945, for a brief period just before the Japanese surrender, the Soviet Union and Mongolia engaged Japanese forces in Manchuria and northeast China.

The Imperial Japanese Navy did not integrate its units into permanent theater commands. The Imperial Japanese Army, 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 that opposed the Western Allies in the Pacific and South East Asia. 




War between Japan and the U.S. was a possibility each nation had been planning for since the 1920s, and serious tensions began with Japan’s 1931 invasion of Manchuria. Over the next decade, Japan continued to expand into China, leading to all-out war between those countries in 1937. Japan spent considerable effort trying to isolate China and achieve sufficient resource independence to attain victory on the mainland; the “Southern Operation” was designed to assist these efforts.

From December 1937, events such as the Japanese attack on USS Panay, the Allison incident, and the Nanking Massacre swung public opinion in the West sharply against Japan. Fearing Japanese expansion, the U.S., the United Kingdom, and France provided loan assistance for war supply contracts to the Republic of China. 

The U.S. ceased oil exports to Japan in July 1941 following Japanese expansion into French Indochina after the fall of France, in part because of new American restrictions on domestic oil consumption. This caused the Japanese to proceed with plans to take the Dutch East Indies, an oil-rich territory. On August 17, Roosevelt warned Japan that the U.S. was prepared to take steps against Japan if it attacked “neighboring countries.” The Japanese were faced with the option of either withdrawing from China and losing face or seizing and securing new sources of raw materials in the resource-rich, European-controlled colonies of Southeast Asia.

The Japanese attack had two  major aims. First, it was intended to destroy important American fleet units, thereby preventing the Pacific Fleet from interfering with Japanese conquest of the Dutch East Indies and Malaya, which would enable and enabling Japan to conquer Southeast Asia without interference. Second, it was meant to intimidate the U.S. into negotiating for terms favorable to Japan. 


Japanese Offensives, 1941 – 42


Following prolonged tensions between Japan and the Western powers throughout most of 1941, the Imperial Japanese Navy and Imperial Japanese Army launched simultaneous surprise attacks on a number of United States and British colonial possessions across the Pacific and east Asia on 7 December 1941 (8 December in Asia/West Pacific time zones). The targets of the first wave of Japanese attacks included the American territories of Hawaii, the Philippines, Guam, and Wake Island, as well as the British territories of Malaya, Singapore, and Hong Kong. Concurrently, Japanese forces invaded southern and eastern Thailand; they were resisted for several hours, before the Thai government signed an armistice and entered an alliance with Japan. Although Japan declared war on the United States and the British Empire, the declaration was not delivered until after the attacks began.

Subsequent attacks and invasions followed during December 1941 and early 1942, leading to the occupation of American, British, Dutch and Australian territories and air raids on the Australian mainland. The Allies suffered many disastrous defeats in the first six months of the war. 

Black and white photo
USS Arizona burned for two days
after being hit by a
Japanese bomb in the attack
on Pearl Harbor. 

The Japanese attack on Pearl Harbor was the centerpiece of the Japanese offensive against the U.S. It was a carrier-based air strike on Pearl Harbor in Honolulu that was conducted without explicit warning, and it crippled the US Pacific Fleet. The attack knocked eight American battleships out of action, destroyed 188 American aircraft, and caused the deaths of 2,403 Americans.

The Japanese had gambled that the United States, when faced with such a sudden massive blow and so much loss of life, would agree to a quick negotiated settlement and allow Japan free rein in Asia. This gamble did not pay off. American losses were not as expansive as initially thought: the American aircraft carriers, which would prove to be more important than battleships, were at sea. Additionally, vital naval infrastructure (fuel oil tanks, shipyard facilities, and a power station), submarine base, and signals intelligence units were unscathed. Even more detrimental to the Japanese plan was the fact the bombing happened while the US was not officially at war, which caused a wave of outrage across the United States. Japan's fallback strategy, relying on a war of attrition to make the US come to terms, was beyond the Imperial Japanese Navy's capabilities. 

On December 8, the United Kingdom, the United States, Canada, and The Netherlands declared war on Japan, followed by China and Australia the next day. Four days after Pearl Harbor, Germany and Italy declared war on the United States. These German and Italian war declarations on the U.S. are widely agreed to have been strategic blunders, as they negated both the benefit Germany gained by Japan's distraction of the US and the reduction in aid to Britain, which both Congress and Hitler had managed to avoid during over a year of mutual provocation. 


South-East Asian campaigns of 1941–42 


Black and white photo
Japanese aerial photo of battleship
HMS Prince of Wales 

(top) and battlecruiser
HMS Repulse under attack. 

Thailand, with its territory already serving as a springboard for the Malayan Campaign, surrendered within 5 hours of the Japanese invasion. The government of Thailand formally allied with Japan on 21 December. To the south, the Imperial Japanese Army had seized the British colony of Penang on 19 December, encountering little resistance. 

Hong Kong was attacked on 8 December; even though Canadian forces and the Royal Hong Kong Volunteers played an important part in the defense of Hong Kong, it fell on 25 December 1941. Japanese forces captured U.S. bases on Guam and Wake Island about the same time. British, Australian, and Dutch forces, already drained of personnel and material by two years of war with Germany, as well as heavily committed elsewhere, were unable to provide much more than token resistance to the battle-hardened Japanese.

As part of a Japanese air attack Japanese aircraft sank two major British warships, the battlecruiser HMS Repulse and the battleship HMS Prince of Wales, off Malaya on 10 December 1941.

Following the Declaration by United Nations (the first official use of the term United Nations) on 1 January 1942, the Allied governments appointed the British General Sir Archibald Wavell to the American-British-Dutch-Australian Command (ABDACOM), a supreme command for Allied forces in Southeast Asia. This gave Wavell nominal control of a huge force, albeit thinly spread over an area from Burma to the Philippines to northern Australia. On 15 January, Wavell moved to Bandung in Java to assume control of ABDACOM. Other areas, including India, Hawaii, and the rest of Australia remained under separate local commands.  

Black and white photo
British forces surrender Singapore
to the Japanese, February 1942

In January 1942, Japanese forces invaded British Burma, the Dutch East Indies, New Guinea, the Solomon Islands, and captured Manila, Kuala Lumpur, and Rabaul. After being driven out of Malaya, Allied forces in Singapore attempted to resist the Japanese during the Battle of Singapore, but they were forced to surrender to the Japanese on 15 February 1942, at which time about 130,000 Indian, British, Australian and Dutch personnel became prisoners of war. The pace of conquest was rapid, as Bali and Timor also fell in February. The rapid collapse of Allied resistance left the "ABDA area" split in two. Wavell resigned from ABDACOM on 25 February, handing control of the ABDA Area to local commanders and returning to the post of Commander-in-Chief, India.

Meanwhile, Japanese aircraft had all but eliminated Allied air power in Southeast Asia and were making air attacks on northern Australia, beginning with a psychologically devastating but militarily insignificant bombing of the city of Darwin on 19 February, which killed at least 243 people. 




Black and white photo
Surrender of US forces at
Corregidor, Philippines,
May 1942

At the Battle of the Java Sea in late February and early March, the Imperial Japanese Navy (IJN) inflicted a resounding defeat on the main ABDA naval force, under Admiral Karel Doorman. The Dutch East Indies campaign subsequently ended with the surrender of Allied forces on Java and Sumatra. Two months later Japanese forces completed their conquest of the Philippines, taking more than 80,000 U.S. soldiers and Marines prisoner. General Douglas MacArthur, commander of U.S. forces in the Philippines, had already withdrawn to Australia, where he assumed his new post as Supreme Allied Commander South West Pacific. The US Navy, under Admiral Chester Nimitz, had responsibility for the rest of the Pacific Ocean. This divided command had unfortunate consequences for the commerce war, and consequently, the Allied war effort in the Pacific, by then under U.S. control. The U.S. assumed this responsibility in the Pacific War because of its geographic proximity to the Pacific, its overwhelming superiority in human and material resources, and its status as the leading Allied Power in this theater. 




Black and white photo of bombing plume rising to the sky
The Bombing of Darwin,
Australia,19 February 1942

In late 1941, as the Japanese struck at Pearl Harbor, most of Australia's best forces were committed to the fight against Axis forces in the Mediterranean Theatre. Australia was ill-prepared for an attack, lacking armaments, modern fighter aircraft, heavy bombers, and aircraft carriers. While still calling for reinforcements from Churchill, the Australian Prime Minister John Curtin called for U.S. support with a historic announcement on 27 December 1941. 

Black and white photo of 4 emaciated men
Dutch and Australian
prisoners-of-war at
Tarsau, in Thailand in 1943,
numbering 22,000.

Many Australians were captured by the Japanese, and at least 8,000 died as prisoners of war. 

The Australian Government ... regards the Pacific struggle as primarily one in which the United States and Australia must have the fullest say in the direction of the democracies' fighting plan. Without inhibitions of any kind, I make it clear that Australia looks to America, free of any pangs as to our traditional links or kinship with the United Kingdom. 

— Prime Minister John Curtin 

Australia had been shocked by the speedy and crushing collapse of British Malaya and the fall of Singapore, in which around 15,000 Australian soldiers were captured and became prisoners of war. Curtin predicted the "battle for Australia" would soon follow. The Japanese established a major base in the Australian Territory of New Guinea, beginning with the capture of Rabaul on 23 January 1942. On 19 February 1942, Darwin suffered a devastating air raid, the first time the Australian mainland had been attacked. Over the following 19 months, Australia was attacked from the air almost 100 times. 

Black and white photo
US General Douglas MacArthur,
Commander of Allied forces in the
South-West Pacific Area,
with Australian Prime Minister John Curtin 

Two battle-hardened Australian divisions were moved from the Middle East for Singapore. Churchill wanted them diverted to Burma, but Curtin insisted on a return to Australia. In early 1942 elements of the Imperial Japanese Navy proposed an invasion of Australia. The Imperial Japanese Army opposed the plan, and it was rejected in favor of a policy of isolating Australia from the United States via blockade by advancing through the South Pacific. The Japanese decided upon a seaborne invasion of Port Moresby, capital of the Australian Territory of Papua, which would put all of Northern Australia within range of Japanese bomber aircraft.

U.S. President Franklin Roosevelt ordered General Douglas MacArthur to formulate a Pacific defense plan with Australia. Curtin agreed to place Australian forces under the command of MacArthur, who became Supreme Commander, South West Pacific. MacArthur moved his headquarters to Melbourne in March 1942, and American troops began massing in Australia. Enemy naval activity reached Sydney in late May 1942, when Japanese midget submarines launched a raid on Sydney Harbour. On 8 June 1942, two Japanese submarines briefly shelled Sydney's eastern suburbs and the city of Newcastle.


Japanese Advance until mid-1942


Japanese expansion across east Asia
and the Pacific to mid-1942

In early 1942, the governments of smaller powers began to push for an inter-governmental Asia-Pacific war council, based in Washington, DC. A council was established in London, with a subsidiary body in Washington. However, the smaller powers continued to push for an American-based body. The Pacific War Council was formed in Washington, on 1 April 1942, with representatives from the U.S., Britain, China, Australia, the Netherlands, New Zealand, and Canada. Representatives from India and the Philippines were later added. The council never had any direct operational control, and any decisions it made were referred to the US-UK Combined Chiefs of Staff, which was also in Washington. Allied resistance, at first symbolic, gradually began to stiffen. Australian and Dutch forces led civilians in a prolonged guerilla campaign in Portuguese Timor. 


Japanese Strategy and the Doolittle Raid


Black and white photo
A B-25 bomber takes off from
USS Hornet as part of the
Doolittle Raid. 

Having accomplished their objectives during the First Operation Phase with ease, the Japanese now turned to the second. Japan planned the Second Operational Phase to expand Japan's strategic depth by adding eastern New Guinea, New Britain, the Aleutians, Midway, the Fiji Islands, Samoa, and strategic points in the Australian area. However, limited resources and U.S. naval intervention in March 1942 stopped Japanese expansion across the south Pacific toward Australia. This intervention, along with the U.S. Doolittle bombing raid against Tokyo in April 1942, provoked Japanese leaders to try a series of riskier offensives against the U.S. naval presence in the central Pacific, specifically at Midway Island.


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