bigpigeon.us webpage WWII - Japan > Overview, updated by RAC 14 May 2022.
Big Pigeon's WW II - Japan module summarizes World War II in east and southeast Asia and the Pacific Ocean area. The War with Japan began in December 1941 with multiple Japanese aerial attacks on United States and British military facilities, the most deadly being at Pearl Harbor in the United States territory of Hawaii.
The War with Japan - a Brief Overview
Japan was at war long before the attacks of December 1941. Japan had invaded China in 1937, initiating the Second Sino-Japanese War, which from December 1941 to August 1945 continued 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, since most United States involvement in the War with Japan was in the Pacific Theater, I give the CBI Theater short shrift.
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
During the following three years, the Allies, and especially the United States, gradually forced the Japanese back to their home islands and the portions of China held by Japan.

The War with Japan ended in August 1945 with the dropping of two atomic bombs on Japanese cities and the entry of the Soviet Union into the War with Japan.
The War with Japan - a Longer Overview
Background: In WWII, the War Department and the Navy Department 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 Ocean was divided into two commands for US military planning and operations.
  • The Southwest Pacific Area, commanded by General Douglas MacArthur, headquartered initially in Brisbane in eastern Australia.
  • The Pacific Ocean Areas, sometimes called the Pacific Theater,, commanded by Admiral Chester Nimitz from Pearl Harbor in Hawaii Territory. The Pacific Area was subdivided into the South Pacific, headquartered in Noumea, New Caledonia, the Central Pacific, and the North Pacific.
Each area command contained a mixture of army, navy, army air force, marine, and coast guard units, although Army units dominated in the Southwest Pacific and Navy units in the South and Central Pacific.
The Pacific Areas
The 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 South Pacific Area, US Navy, Marine Corps and Army forces advanced northwest through the Solomon Islands.
  • In the Southwest Pacific Area, US Army and Australian forces advanced northwest securing the New Guinea tail.
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.
  • Near the end of 1943, Nimitz began to reduce Navy 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
In less than a year beginning in November 1943, the Central Pacific Campaign advanced US forces in a semicircular path, from the Gilbert Islands in the bottom right of the following map to the Palau Islands in the bottom left. There were four major operations, each consisting of multiple amphibious landings of Marine and Army combat troops, supported by the now-massive American battle fleet.
  1. November 1943  - the Gilbert Islands - Tarawa and Makin.
  2. ​Kwajalein and Enewetok in the Marshall Islands.
  3. - the Mariana Islands - Guam, Saipan and Tinian.
  4. - the Palau Islands - 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 now 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
 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 two 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 three United States campaigns in the WW II Pacific Theater, 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 (the US Sixth and Eighth Armies).
The Philippine IslandsThe Philippine Islands
  • Iwo Jima, February - March 1945 (three Marine Corps divisions fought).
  • Okinawa, April - June 1945 (four Army divisions and three Marine divisions organized into the US Tenth Army fought; heavy Navy losses from Japanese kamikaze aircraft).
Iwo Jima and Okinawa
Iwo Jima and Okinawa
Sources for the WWII -  Japan Overview 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.