Pacific War

The Pacific War was the part of World War II fought between Japan and the Allies. It took place in East and Southeast Asia, the Pacific and Indian Oceans, and Oceania. This was the largest area of fighting in the whole war, with many big naval battles happening.

It began when Japan attacked many places, including the American base at Pearl Harbor in Hawaii in December 1941. Japan took control of several islands and areas, but the Allies slowly pushed back. Important battles included the Battle of Midway, which turned the war in the Allies' favor.

As the war went on, the Allies used a strategy called island hopping to move closer to Japan. This led to battles on islands like Iwo Jima and Okinawa. The war ended after the United States atomic bombings of Hiroshima and Nagasaki and the Soviet invasion of Manchuria in August 1945. Japan surrendered unconditionally soon after, ending World War II.

Names of the war

During World War II, the fight between Japan and the Allies in the Pacific area was often just called the war against Japan, especially in countries that were part of the Allies. In the United States, people commonly used the term "Pacific theater" to describe this part of the war. The United States also saw the fighting in China Burma India theater as a separate area from the larger fight in the Asiatic-Pacific theater.

Japan called this conflict the "Greater East Asia War." They chose this name on December 10, 1941, to include both their war with Western countries and their ongoing fight in China. Japan said this war helped Asian nations gain independence from Western powers. After World War II, during the time when Allied forces oversaw Japan, these names were not allowed in official documents, though people still used them sometimes. The war is now officially called the Pacific War. Some also refer to it as the "Fifteen Years' War," starting from 1931 and ending in 1945.

Participants

Allies

The main countries fighting against Japan were China, the United States, and the British Empire. China had already been fighting Japan since 1937. The United States and its territories, like the Philippine Commonwealth, joined the war after Japan attacked Pearl Harbor in 1941. This led Japan to declare war on several other countries, including Australia, Canada, New Zealand, and the United Kingdom. The Dutch government-in-exile also fought back, controlling the Dutch East Indies.

Other groups helped too, such as the Hukbalahap, Korean Liberation Army, Free Thai Movement, Việt Minh, Khmer Issarak, and Malayan Peoples' Anti-Japanese Army. The Soviet Union had small fights with Japan in 1938 and 1939 but stayed neutral until 1945, when it joined the Allies and attacked Japanese-held areas.

Axis powers and aligned states

Countries that supported Japan included Thailand and groups in areas Japan controlled, like Manchukuo and parts of China under the Wang Jingwei regime. Japan also used soldiers from its colonies, such as Korea and Taiwan, and formed local groups in places like Hong Kong, Singapore, the Philippines, and Dutch East Indies.

Germany and Italy had small roles, mainly using submarines and ships in the Indian and Pacific Oceans.

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. In the United States, people often talked about two main parts of the war: the Pacific theater and the China Burma India Theater (CBI). These were not actual commands that controlled troops.

In the Pacific, the Allies split their forces into two main groups, called the Pacific Ocean Areas and the Southwest Pacific Area. The Imperial Japanese Navy did not organize its ships into fixed groups. The Imperial Japanese Army had already set up armies for Manchukuo and China and later created the Southern Expeditionary Army Group to lead its forces in South East Asia. This group led most of the Japanese army troops fighting against the Western Allies in the Pacific and South East Asia.

Historical background

Conflict between China and Japan

The war between China and Japan began in 1931 when Japan invaded Manchuria without declaring war. They wanted resources for their growing economy. By 1937, Japan had taken control of Manchuria and moved deeper into China. A battle at the Marco Polo Bridge on July 7, 1937, led to full-scale war. China’s Nationalist Party and Communist forces paused their own fighting to work together against Japan. Japan took many cities, including Nanjing, but faced strong resistance.

Japan kept pushing into China, taking more land and fighting long battles. However, they couldn’t fully defeat the Chinese army, which kept fighting from new bases. Japan also tried to invade areas near the Soviet Union but were stopped. By 1941, the fighting had settled into a stalemate with Japan controlling much of southern and eastern China, while Chinese forces held out in other areas.

Tensions between Japan and the West

Japan wanted more resources like oil and wanted to expand its power. They built up their military and prepared for possible conflict with Western countries. In response, countries like the United States stopped selling oil and other important supplies to Japan. This made Japan very concerned about their economy and led them to plan for war to get the resources they needed.

Japanese preparations

Japan started planning for war with Western powers in early 1941. They wanted to take control of areas rich in resources, like the Dutch East Indies and Malaya, to overcome the loss of supplies from embargoes. Their plan included attacking the Philippines, Wake Island, and Guam. Japan hoped to quickly seize these areas and then defend them against any counterattacks. They believed this would force other countries to negotiate for peace, allowing Japan to keep the lands they had taken.

Main article: Second Sino-Japanese War

Japanese offensives, 1941–1942

Following tensions between Japan and Western powers, Japanese forces launched surprise attacks on the United States and the British Empire on December 7, 1941. These attacks included locations like Hawaii, the Philippines, Guam, Wake Island, Malaya, Singapore, and Hong Kong. Japan also invaded southern and eastern Thailand, where they met brief resistance before Thailand agreed to work with Japan.

Attack on Pearl Harbor

Main article: Attack on Pearl Harbor

On December 7, 1941, Japanese aircraft attacked the US naval base at Pearl Harbor in Hawaii. This surprise attack damaged many American ships and aircraft. The Japanese hoped this would weaken the US enough to negotiate peace, but instead, it united the United States against Japan. The United Kingdom, the United States, Canada, and the Netherlands all declared war on Japan shortly after the attack.

South-East Asian campaigns of 1941–1942

Thailand quickly surrendered to Japan and allied with them. Japan also captured British colonies like Penang and Hong Kong, as well as American bases on Guam and Wake Island. British, Australian, and Dutch forces, already fighting in other parts of the world, could only put up small resistance. Two large British warships were sunk by Japanese aircraft off Malaya in December 1941.

In January 1942, Japan invaded parts of Burma, the Dutch East Indies, New Guinea, and the Solomon Islands. They captured important cities like Manila, Kuala Lumpur, and Rabaul. Allied forces in Singapore tried to resist but were forced to surrender in February 1942. Japan also bombed northern Australia, starting with an attack on Darwin in February 1942.

Philippines

Main article: Philippines campaign (1941–1942)

Japanese bombers attacked American airfields in the Philippines on December 8, 1941, destroying many planes. By December 13, all major airfields were destroyed. Most American ships left the Philippines, leaving only ground troops and a few aircraft to defend. Japanese forces landed on Luzon in December 1941 and moved toward Manila. American and Filipino forces retreated to the Bataan Peninsula and the island of Corregidor. After months of fighting with little supplies, Bataan fell in April 1942, and Corregidor surrendered in May 1942.

Threat to Australia

Australia was unprepared for war and had most of its forces fighting in other places. After seeing how quickly Japan overpowered forces in Malaya and Singapore, Australia asked the United States for help. Japan set up a base in New Guinea and attacked mainland Australia for the first time in February 1942 when they bombed Darwin. Over the next year, Australia was attacked from the air nearly 100 times. In early 1942, Japan considered invading Australia but decided instead to try to cut Australia off by advancing through the South Pacific. American and Australian forces prepared to defend Australia together.

Allies re-group, 1942–1943

In early 1942, smaller Allied nations formed a council to coordinate their efforts in the Asia-Pacific region. This group, called the Pacific War Council, included leaders from Britain, China, Australia, the Netherlands, New Zealand, and Canada, among others. The council helped plan strategies but did not control military operations directly.

Japan planned to expand its control by capturing areas like New Guinea, the Aleutians, and the islands of Fiji and Samoa. However, their plans faced challenges. American aircraft attacked Japanese forces, and the United States carried out a raid on Japan itself, boosting American spirits. The Japanese also planned to capture the island of Midway to draw out the American navy, but American codebreakers learned of the plan in advance. This led to a major battle at Midway, where American forces surprised and defeated the Japanese fleet, marking a turning point in the war.

The Japanese also tried to capture Port Moresby in New Guinea but were stopped by Allied forces. Battles continued in places like the Solomon Islands and Guadalcanal, where both sides fought fiercely. The Allies gradually gained the upper hand, and by early 1943, they had successfully defended key positions against Japanese attacks. These battles showed that the Allies could withstand Japanese advances and begin to push back.

Stalemate in China and Southeast Asia

China 1942–1943

In early 1942, Japanese troops in China tried to move south but were stopped by Chinese forces, who won a key battle at Changsha. Later, Japan launched another attack to find American airmen and punish those who helped them. This effort was stopped by Chinese troops. During this time, Japan used harmful methods that spread diseases, causing many deaths.

In November 1943, Japanese forces attacked Changde. The Chinese fought hard, and although the Japanese took the city, the Chinese held them long enough to bring in reinforcements. The Chinese then cut off supplies, forcing the Japanese to retreat.

Burma 1942–1943

Main article: Burma campaign (1942–1943)

After Japan took control of Burma, there were problems in nearby areas, including a serious food shortage. Despite this, British leaders planned to push back against Japan in Burma.

The British started an attack to capture an important island with a port and airfield. However, they faced strong Japanese defenses and were unable to move forward. A Japanese division counterattacked, forcing the British to withdraw to the Indian border.

Leaders believed the British needed better training for jungle fighting. To boost morale, they highlighted a long-distance raid by special forces, though it did not achieve major results. In 1943, new leadership was appointed to improve organization and training for the forces in the region. The Thai army tried to invade China but was pushed back by Chinese troops.

Allied offensives, 1943–1944

After a big battle called Midway, the United States started making many more ships, planes, and training more pilots. Japan, however, could not keep up because they did not have enough factories or resources. The Allies began moving across the Pacific, taking control of islands one by one. They sometimes skipped over strong Japanese bases to get closer to Japan itself.

The US Navy did not look for big battles with the Japanese fleet. Instead, they kept moving forward, knowing that Japan’s lack of oil would make it hard for them to stop the Allies.

Allied offensives on New Guinea and up the Solomons

Main articles: New Guinea campaign, Operation Cartwheel, and Bougainville campaign

In June 1943, the Allies started a plan called Operation Cartwheel to take back islands like the Solomon Islands and New Guinea. They wanted to cut off a big Japanese base at Rabaul. They fought many battles to take back places like Salamaua, Lae, New Georgia, and Bougainville.

Invasion of the Gilbert and Marshall Islands

Main article: Gilbert and Marshall Islands campaign

In November 1943, US Marines fought hard to take an island called Tarawa. After this, they learned to plan better for future battles. In early 1944, they moved on to the Marshall Islands.

Cairo Conference

On 22 November 1943 US President Franklin D. Roosevelt, British Prime Minister Winston Churchill, and ROC Generalissimo Chiang Kai-shek met in Cairo, Egypt, to discuss a strategy to defeat Japan. The meeting was also known as the Cairo Conference and concluded with the Cairo Declaration.

Submarine warfare

Main article: Allied submarines in the Pacific War

During the war, submarines from the United States, Britain, and the Netherlands played an important role. They attacked Japanese ships, cutting off supplies of oil and troops. By early 1945, Japan’s oil supplies were so low that their navy could not move easily.

Japanese leaders said they sank many Allied submarines, but in fact, only a small number were lost. American submarines were very effective, sinking many Japanese ships and helping to rescue pilots who had been shot down.

American submarines faced dangers, with many not returning from their missions. The Japanese also lost many submarines during the war.

Japanese offensives in Asia, 1944

Japanese counteroffensives in China, 1944

In mid-1944, Japan gathered over 500,000 soldiers in China and started its biggest ground attack of the war, called Operation Ichi-Go. The aim was to connect Japanese areas in China and French Indochina by land and capture important air bases used by American bombers. Although Japan faced about 100,000 losses, it took control of more land in China before the operation stopped near Guangxi. However, Japan did not gain any major strategic benefits overall. Most Chinese forces managed to move away and later attacked Japanese positions at the Battle of West Hunan. Japan's losses in the Pacific made it hard for them to win in China. The operation caused confusion in the areas it affected, which helped Chinese Communist guerrillas gain more control in rural areas.

Japanese offensive in India, 1944

Main article: Burma Campaign 1944

After some difficulties for the Allies in 1943, they prepared to move into Burma from several directions in 1944. Chinese and American troops, led by General Joseph Stilwell, started extending a road from India into northern Burma, while Indian troops advanced along the coast in Arakan Province. In February 1944, Japanese forces tried to counter-attack in Arakan but were defeated at the Battle of the Admin Box.

In March 1944, Japan launched a major attack into India, called Operation U-Go, led by Lieutenant General Renya Mutaguchi. The Allied forces, led by General Slim, planned to retreat to the Imphal plain and make the Japanese fight with long supply lines. Although they were slow to react at first, Allied troops gathered around Imphal by April. A Japanese division reached Kohima in Nagaland, cutting off the main road to Imphal, but could not capture Kohima. In April, Japanese attacks on Imphal failed, and Allied forces relieved Kohima and pushed Japanese troops back.

The Japanese troops suffered greatly from lack of supplies and disease, especially after the rainy season began in May. By June, Allied forces from Kohima and Imphal met and broke the Japanese siege of Imphal. Japan ended the operation in July after losing over 50,000 troops, mostly from starvation and disease. This was Japan's worst defeat up to that point.

While the attack in Arakan was stopped, American and Chinese forces continued to move forward in northern Burma. By the end of the monsoon season, they had captured a key airfield at Myitkyina, making it easier to supply China from India over "The Hump".

Beginning of the end in the Pacific, 1944

In May 1943, the Japanese prepared a plan called Operation Z to use their naval power against American forces. The plan aimed to protect Japan's defenses in the Pacific. By 1943–1944, Allied forces were moving toward a key Japanese base at Rabaul. The Japanese changed their plan and focused on defending a smaller area including the Marianas, Palau, Western New Guinea, and the Dutch East Indies.

In the Central Pacific, American forces began an offensive in November 1943 with landings in the Gilbert Islands. They captured islands like the Gilberts and Marshalls, making it hard for Japan to defend distant locations. In February 1944, US Navy forces attacked a major Japanese naval base at Truk, causing heavy losses to Japanese aircraft and ships. The Japanese navy had to move their ships and could no longer effectively fight the Americans.

Marianas and Palaus

On March 12, 1944, the US planned to capture the Northern Marianas, targeting Saipan by June 15. This would help disrupt Japanese airpower, allow building bases closer to Japan, and provide airfields for bombers to reach Japan. American forces landed on Saipan on June 15, facing strong Japanese resistance. After intense fighting, they captured key areas by late June. A large Japanese attack on July 6 was repelled. By July 9, organized resistance ended, though some hidden Japanese soldiers remained.

A month later, the US recaptured Guam and captured Tinian. Saipan and Tinian were used by the US military to bomb Japan. Japanese attacks on these bases continued until the war’s end. The invasion of Peleliu in September was tough, with heavy losses for US forces. The battle lasted two months, showing new Japanese tactics.

Philippine Sea

When Americans landed on Saipan, Japan launched plan A-GO. The Japanese sent a large carrier force against the US Fifth Fleet. The battle on June 19 was one of the largest carrier battles ever. Strong American defenses destroyed many Japanese planes and ships. The Japanese lost three carriers and many aircraft and pilots, severely weakening their navy’s ability to fight at sea.

Leyte Gulf, 1944

After losing at the Philippine Sea, Japan had to choose between attacking the next American landing or letting them cut supply lines. Japan chose to attack the American beachhead at Leyte in October 1944. They split their forces into three groups to try to destroy American ships.

American forces attacked the Japanese ships, sinking many, including battleships and carriers. The battle was very large and ended with Japan losing many ships and men. This defeat cut Japan off from important resources.

Philippines, 1944–1945

On October 20, 1944, US forces landed on Leyte in the Philippines. They faced heavy rains and tough terrain but continued to advance. By December, they had control of Leyte. Landings on Mindoro followed in December 1944, leading to the invasion of Luzon in January 1945. American forces pushed inland, taking important areas and moving toward Manila. The battle for Manila was very hard and caused many civilian deaths.

Fighting continued on Luzon, with many Japanese troops killed. The US also invaded other Philippine islands like Palawan, Mindanao, Panay, Cebu, Negros, and islands in the Sulu Archipelago. These islands helped US forces attack targets in the Philippines and nearby seas.

Final stages

See also: End of World War II in Asia and Aftermath of World War II

Allied offensives in Burma, 1944–1945

Main article: Burma campaign (1944–1945)

In late 1944 and early 1945, the Allies launched offensives into Burma to recover the country, including its capital, Rangoon, before the rainy season began in May. These offensives were fought mainly by British, Chinese, and American forces, with help from Thailand, the Burma National Army, and the Indian National Army. The land forces came mostly from the United Kingdom, British India, and Africa.

The Indian XV Corps advanced along the coast, capturing Akyab Island and other key locations, establishing airfields for support. The Chinese Expeditionary Force and American forces also moved forward, linking up in northern Burma. The Japanese tried to stop the Allies by moving behind the Irrawaddy River, but the British Fourteenth Army outflanked them.

In February, the Fourteenth Army secured areas across the Irrawaddy. In March, mechanized units captured Meiktila, causing confusion in Japanese defenses. Mandalay fell soon after. By April, the Fourteenth Army moved toward Rangoon but was delayed. An amphibious operation, Operation Dracula, was launched on May 1 to capture Rangoon, but the city had already been evacuated by the Japanese. The Allies secured their supply lines.

Japanese forces attempting to retreat suffered heavy losses, and overall, they lost around 150,000 men in Burma. The Allies were preparing for landings in Malaya when Japan surrendered.

Iwo Jima

Main article: Battle of Iwo Jima

The island of Iwo Jima was important because it could serve as a landing site for planes and protect American ships. The Japanese built strong defenses there, including caves and hidden guns. In February 1945, American Marines landed on Iwo Jima and faced fierce resistance. The battle was very tough, and many soldiers on both sides were hurt or lost their lives. The Americans finally took control of the island by the end of March.

Okinawa

Main article: Battle of Okinawa

The battle for Okinawa was one of the largest and hardest fights in the Pacific. Okinawa was important because it could give America air bases to bomb Japan and support an invasion. American forces landed on Okinawa in April 1945 and faced strong Japanese defenses. The fighting was very tough, especially in the south of the island. The battle lasted longer than expected and caused many casualties on both sides. Organized Japanese resistance ended in June, but the campaign officially ended in July.

China, 1945

Main articles: Battle of West Hunan and Second Guangxi Campaign

In 1945, despite earlier Japanese successes, they were losing in Burma and facing attacks from Chinese Nationalist forces and Communist guerrillas. The Japanese began an operation in West Hunan to seize airfields and railroads. Chinese forces, supported by American aircraft, fought back successfully. Later, Chinese forces pushed back Japanese advances in Henan and Hubei and went on to retake Hunan and Hubei. By August 1945, Chinese forces had also retaken Guangxi.

Borneo, 1945

Main article: Borneo campaign (1945)

The Borneo campaign was the last major campaign in the Southwest Pacific. Between May and July 1945, Australian forces, supported by American and Australian naval and air forces, launched attacks on Japanese forces in Borneo. The campaign began with a landing on Tarakan in May, followed by assaults on Labuan and Brunei in June, and North Borneo. The final major amphibious assault happened at Balikpapan in July.

Although some thought the campaign was not necessary, it helped isolate Japanese forces, capture oil supplies, and free prisoners of war who were in very bad conditions. Sadly, only a few prisoners survived from one of the worst camps in Sandakan.

Landings in the Japanese home islands (1945)

Main articles: Japan campaign, Operation Downfall, and Air raids on Japan

Battles on islands like Iwo Jima and Okinawa were very hard and caused many losses on both sides. The Japanese used special attack planes called kamikazes to try to hurt the Allies. The United States considered blockading Japan and bombing it from the air to force a surrender.

As bombing became more important, a new command was created to oversee all US strategic bombing in the Pacific. Japanese cities were heavily bombed, and large areas were destroyed. In March 1945, Tokyo was bombed, causing huge damage and many casualties.

Atomic bombs

Main article: Atomic bombings of Hiroshima and Nagasaki

In August 1945, the United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki. This was the first time nuclear weapons were used in war. Many people lost their lives as a result of these bombings. The bombings led to debates about whether they were necessary to end the war or if other methods could have been used.

Soviet entry

In August 1945, the Soviet Union entered the war against Japan, invading Manchuria. This was important because it showed Japan that the Soviets would no longer try to help them negotiate peace. The Soviet forces quickly took over areas in Manchuria and northern Korea.

Surrender

Main article: Surrender of Japan

After months of attacks from the air and sea, the atomic bombings, and the Soviet invasion, Japan decided to surrender. On August 15, 1945, Emperor Hirohito announced Japan’s surrender. The formal surrender document was signed on September 2, 1945, marking the end of World War II in the Pacific.

Casualties

Total losses for the United States in the Pacific War included around 161,000 killed and 248,000 wounded. Over half of these losses happened between July 1944 and July 1945. The US and its allies lost nearly 200 warships and almost 30,000 aircraft.

China faced very heavy losses, with estimates of around 14 to 15 million people dead. This included both soldiers and civilians. Many died from disease, starvation, or attacks.

Other Allied nations also suffered losses. Britain lost around 235,000 people, including about 82,000 killed. Australia lost about 45,841, with 17,501 killed. New Zealand, Canada, and other nations also had casualties.

On the Axis side, Japan lost over 2 million soldiers and 800,000 civilians. The Japanese Navy lost many warships, including battleships and aircraft carriers. Germany lost a small number of submarines and auxiliary ships in the Pacific.