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bigpigeon.us webpage WWII Japan > Japan Summary, © 2026 by Robert A. Christiansen, updated by RAC 28 Dec 2025
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 The War with Japan began in December 1941 with multiple Japanese aerial attacks on United States and British military facilities, the deadliest being at Pearl Harbor in the United States territory of Hawaii.
​:::::::::::::::::::::::::::::::::::::::::::::::::: Scope of Big Pigeon's WWII Japan Submodules ::::::::::::::::::::::::::::::::::::::::::::::::::
Preliminary webpages provide contextual material: Japan's series of victories in the first five months of the war: The pivotal naval air battles of Coral Sea and Midway: The Allied response beginning with Papua and Guadalcanal:     Military action in Alaska:​ The massive United States Central Pacific campaign beginning with Tarawa and ending with Peleliu: ​The US recapture of the Philippine Islands:   ​​ Acquiring forward bases for the invasion of Japan: The final months of the Japanese Empire: ​Concluding WWII Japan webpages: Military action on the Asian mainland: About the above links to WWII Japan submodules:​
  • A concise list of these links is above the page header.
  • WWII Hub lists all WWII Japan subpages.
  • Some webpages are incomplete.
​  :::::::::::::::::::::::::::::::::::::::::::::::::::::: The War with Japan - a Brief Summary ​:::::::::::::::::::::::::::::::::::::::::::::::::::::: 
Japan was at war long before the attacks of December 1941. Japan had invaded China in 1937, initiating the Second Sino-Japanese War, which continued from December 1941 to August 1945 in what became known as the China-Burma-India (CBI) Theater and was a major part of the War with Japan.
  • ​The majority of deaths in the War with Japan occurred in the CBI Theater among Chinese civilians and troops.
  • However, the War with Japan was won by Allied forces in the Pacific Theater, a vastness encompassing the southwest, south, central and north Pacific oceans.
  • Thus the Pacific Theater rather than the China-Burma-India Theater receives the brunt of attention herein.
Japanese Home Islands
Japanese Home Islands
For the 70 years before 1941,  Japan expanded from the home islands, shown on the above map to a sizable empire. Japan hoped to expand further into China and into the resource-rich colonies of southeast Asia and the Netherlands Indies, but was constrained by opposition from the United States and the British Empire.

Despairing of a negotiated solution to its perceived grievances, Japan launched surprise attacks on December 7-8 against the United States and the British Empire in the Pacific area and in east and southeast Asia.

For the next five months, the Japanese military was wildly successful, as shown on the accompanying map. ​
The Japanese War
The Japanese War
In the Pacific Theater during the following three years, the Allies, led the United States, gradually forced the Japanese back to their home islands, the Netherlands Indies, and the portions of mainland Asia still held by Japan.

The War with Japan ended in August 1945 with the entry of the Soviet Union into the War with Japan and the dropping of two atomic bombs on Japanese cities.
​  ::::::::::::::::::::::::::::::::::::::::::::::::::: The War with Japan - a Longer Summary ​:::::::::::::::::::::::::::::::::::::::::::::​:::::​:::::

Background: In WWII, the United States War and Navy Departments had not yet been combined into what is now the Department of Defense. The Air Force was part of the Army, while the Marine Corps was closely associated with the Navy.
For much of WWII, the Pacific area was divided into two commands for US military planning and operations.
  • The Southwest Pacific Area, commanded by army General Douglas MacArthur, headquartered initially in Brisbane in eastern Australia.
  • The Pacific Ocean Areas, commanded by navy Admiral Chester Nimitz from Pearl Harbor in Hawaii Territory. The Pacific Ocean Areas were subdivided into the South Pacific, headquartered in Noumea, New Caledonia, the Central Pacific, under Admiral Nimitz's direct control, and the North Pacific, headquartered in Alaska Territory.
Each area command contained a mixture of army, navy, marine, and coast guard units, although Army units dominated in the Southwest Pacific and Navy and Marine Corps units in the South and Central Pacific.
The Pacific Areas
The Pacific Areas
  ...................................................... The South and Southwest Pacific Areas ......................................................
From August 1942 to November 1943, most US combat in the War with Japan took place in the area shown on the following map.
  • In the Southwest Pacific Area, US Army and Australian forces advanced northwest securing eastern New Guinea.
  • In the South Pacific Area, US Navy, Marine Corps and Army forces advanced northwest through the Solomon Islands.
This two-pronged movement, initiated to protect Australia against further Japanese threats, evolved into the goal of neutralizing the major Japanese base at Rabaul on the northern coast of New Britain.
Early War with Japan Combat
~ 1943 War with Japan Combat
The Southwest Pacific Area included the Philippine Islands, which had been lost in May 1942, and which MacArthur was determined to recapture.
  • After securing the New Guinea tail in 1943, MacArthur's forces leapfrogged in 1944 to the head of New Guinea and then beyond, to the island of Morotai in the Netherlands Indies.
As 1943 progressed, Admiral Nimitz began to reduce Navy and Marine involvement in the South Pacific to prepare for the pending Central Pacific Offensive.
The Southwest Pacific Theater
South & Southwest Pacific Battle Sites - Aug '42 - Sep '44
  ............................................................... The Central Pacific Areas ...............................................................
In less than a year beginning in November 1943, the Central Pacific Campaign advanced US forces in a counterclockwise semicircular path, from the Gilbert Islands in the bottom right of the following map to the Palau Islands in the bottom left. The four major operations each consisted of multiple amphibious landings of Marine and Army combat troops, supported by the now-massive American battle fleet.
  1. The Gilbert Islands of Tarawa and Makin.
  2. ​Kwajalein and Eniwetok in the Marshall Islands.
  3. The Mariana Islands of Saipan, Guam, and Tinian.
  4. The Palau Islands of Peleliu and Anguar.
The Marshall Islands were needed for fleet anchorages. The Mariana Islands were needed for the subsequent strategic bombing of Japan. Armchair historians sometimes question whether the Gilbert and Palau Islands operations were necessary.
Central Pacific Battle Sites - Nov '43 - Nov '44
Central Pacific Battle Sites - Nov '43 - Nov '44
  ..................................................... The Scope of WWII Pacific Operations .....................................................
 Except for Pearl Harbor, Midway, and the Aleutian Islands, major Pacific Theater combat before February 1945 took place in areas shown on the accompanying map,  thousands of miles west and south of Pearl Harbor.

Contained within this map are the areas shown in the previous three maps.

​For scale, note the superimposed outline of the continental United States. The red line shows the movement of General MacArthur's headquarters from Brisbane, Australia back to Manila on the island of Luzon in the Philippines. 
The Southwest Pacific
The Pacific Ocean Near Australia
  ................................................... The Final Campaigns in the Western Pacific ...................................................
The three final United States campaigns in the WWII Pacific areas, during the last year of WWII, were also the most costly in US lives lost in the War with Japan.
  • The recapture of the Philippines, October 1944-August 1945 by the US Sixth and Eighth Armies.
The Philippine IslandsThe Philippine Islands
  • Iwo Jima, February-March 1945 by three Marine Corps divisions.
  • Okinawa, April-June 1945 by four Army divisions and three Marine divisions organized into the US Tenth Army; heavy Navy losses from Japanese kamikaze aircraft.
Iwo Jima and Okinawa
Iwo Jima and Okinawa
​  ::::::::::::::::::::::::::::::: Sources for Big Pigeon's WWII Japan > Japan Summary webpage :::::::::::::::::::::::::::::::​
  • The Japanese Home Islands map is courtesy of nationalgeographic.org.
  • The Pacific Areas map courtesy of https://www.ibiblio.org/hyperwar/USA/USA-P-Papua/index.html.
  • https://upload.wikimedia.org/wikipedia/commons/7/70/The_New_Guinea_Area_-_Allied_Advance_%28AMH-43%29.jpg
  • The Central Pacific Battle Sites map is excerpted from the Scene of Battle map found in the Marines in the Central Solomons volume of the United States Marine Corps Operations in WW II.
  • The Philippine Islands map is courtesy of https://people.umass.edu/~chonal/framesetwq.htm
  • The Iwo Jima and Okinawa map is courtesy of https://www.ibiblio.org/hyperwar/USMC/USMC-M-IwoJima/index.html.
  • The timeline at http://www.historyplace.com/unitedstates/pacificwar/timeline.htm is informative.