During the 1930s, the United States found itself in a situation that would end up changing it forever. Relations between the US and Japan had been strained ever since the latter began their conquests in China and Southeast Asia. Although the Americans tried to maintain their policy of non-intervention, they eventually found themselves forced into action in the South West Pacific Theater of Operations.

American isolationism came to an abrupt end when a series of failed negotiations and a tightening trade embargo led Japan to launch the December 7, 1941 attack on Pearl Harbor. Japan’s surprise assault on the American naval base launched a conflict in the Pacific Theater that would last four years.

From December 8, 1941 to September 2, 1945, the Pacific was a battleground. The armed forces of the United States and its Allies fought Japan in a series of battles throughout the Pacific, each side trying to get a leg up on the other. Over the course of the war, the following major campaigns were launched, each one an attempt to take or hold onto different islands or advantageous locations.

First Philippines Campaign

Japanese troops landing on Corregidor

Japanese troops landing on Corregidor

The first of two campaigns in the Philippines, the initial struggle in the South West Pacific Theater between the Filipino forces, backed by American troops, and Japan started shortly after the attack on Pearl Harbor. The United States, still trying to recover from the stunning attack, proved to be outmatched by the Japanese forces.

Over the course of the Battles of Bataan and Corregidor, the lengthy campaign lasted until May 8, 1942, when Japan occupied all of the Philippines.


Dutch East Indies Campaign

HMS Exeter sinking during the battle of the Coral Sea 28 February, 1942

HMS Exeter sinking during the battle of the Coral Sea, 28 February 1942

Consisting of four battles, the Dutch East Indies campaign was partly the reason for the attack on Pearl Harbor. Fearing the US Pacific Fleet would interfere in the takeover of the Dutch East Indies, the Japanese leadership knew they would have to take the Americans out of the equation.

Battles were fought at Badung Strait, twice in the Java Sea, and Sunda Strait, eventually leading to the Japanese occupation of the Dutch East Indies for three and a half years.




Guadalcanal Campaign

US Marines storming the beaches on Guadalcanal, 7 August 1942

US Marines storming the beaches on Guadalcanal, 7 August 1942

In the earlier months of the War in the Pacific, the Allies were forced to remain on the defensive. On August 7, 1942, Allied forces sought to change that and launched an invasion of Guadalcanal, Tulagi, and the southern Solomon Islands. For the US and the Allies to be able to gain any ground in the Pacific, they would need to relieve supply and communication routes being blocked by Japan.

The invading Allied troops greatly outnumbered Japan’s forces, eventually earning a much-needed victory for the Allies. Comprised primarily of United States Marines, the Allies surprised Japan with the invasion and were able to initially secure the islands of Tulagi and Florida, as well as an airfield on Guadalcanal. With the Japanese forced back from Guadalcanal, the Allies secured their resupply routes and the opportunity to turn the war into an offensive one.


Solomon Islands Campaign

The Solomon Islands campaign spanned the duration of the War in the Pacific, starting in January 1942 and ending mere weeks before Japan officially surrendered. Japan suffered heavy losses in the Battles of Kula Gulf, Kolombangara, Vella Gulf, Vella Lavella, Empress Augusta Bay, and Cape St. George, with an estimated 86,000 men killed and 1,500 aircraft lost.

Though Japan saw successes at the Battle of Vella Lavella and the Battle of Kolombangara, the Allies ultimately emerged the victors, cutting off Japan’s ability to block Australia and New Zealand from American resources.


New Guinea Campaign

Explosion of the USS <em>Lexington</em> (CV-2), 8 May, 1942

Explosion of the USS Lexington (CV-2), 8 May 1942

The New Guinea campaign proved to be one of the most active campaigns of the war, comprising 14 separate battles that occurred between May 1942 to November 1944. The Battle of the Coral Sea was the first in the campaign and ended ambiguously, with the United States earning a strategic victory by stopping a Japanese advance, but Japan inflicting heavier losses. Since the failed attempt in the Coral Sea, Japan failed to make much progress in the New Guinea Campaign, with the Allies scoring a victory in each of the 13 battles and smaller campaigns that followed.




Timor Campaign

Timorese village burning, 12 December 1942

Timorese village burning, 12 December 1942

For the span of a year, Japanese and Allied forces were locked in battle in both the Portuguese and Dutch parts of the island of Timor. When the Japanese invaded the island on February 20, 1942, they were met by a small force of Australia, UK, and Dutch East Indies forces.

The campaign was fought by approximately 15,000 men and Japan suffered the greatest loss of almost 4,000. Though Japan may have suffered more casualties, the Timor campaign wound up being a tactical Japanese victory as Australian troops were forced to withdraw beginning in December of 1942.

Though Japan retained control of Timor, troops locked up in that campaign were unable to assist in the New Guinea Campaign.


Second Philippines Campaign

General Douglas MacArthur wading ashore at Leyte, 20 October 1944

General Douglas MacArthur wading ashore at Leyte, 20 October 1944


Though Japan took the Philippines at the start of the war, the United States and the Allies were determined to regain control of the archipelago. The eleven battles fought during the campaign proved that after the Battle of Midway in 1942, Japan could not get a clear victory against the Allied forces.

Each battle, from Leyte Gulf to Maguindanao, liberated more and more territory of the Philippines. The campaign came to an end when Japan’s forces were ordered to surrender on August 15, 1945, after the atomic bombings of Hiroshima and Nagasaki.



Borneo Campaign

Australian machine gunners on Borneo, 2 July 1945

Australian machine gunners on Borneo, 2 July 1945

In hopes of ending Japan’s control of valuable natural resources and isolating their forces from other parts of the Netherlands East Indies, the Allies launched the Borneo Campaign. Three battles were fought between May and July of 1945, and were the last major amphibious assaults in the South West Pacific Theater.

Approximately 50,000 servicemen took part in the campaign and by the time it ended with Japan’s surrender, the Allies had suffered 2,100 casualties and Japan 4,700.

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