The Pacific

On 7 December 1941, 353 Japanese carrier aircraft attacked Oʻahu in two waves. The raid killed 2,403 Americans and sank or damaged twenty-one U.S. ships, with the battleships at Pearl Harbor taking the most visible losses. The three U.S. Pacific Fleet aircraft carriers were away from the harbor and survived.

Japan's southern offensive struck British, American and Dutch positions almost simultaneously after Pearl Harbor. Malaya and Singapore fell by 15 February 1942, Java capitulated in March, Bataan surrendered on 9 April and the remaining U.S.-Filipino forces on Corregidor surrendered on 6 May. At Singapore alone about 80,000 Commonwealth troops entered captivity.

The Coral Sea was the first carrier battle in which the opposing surface fleets did not engage each other directly. Japan sank the carrier Lexington and other U.S. vessels and damaged Yorktown; American aircraft sank the light carrier Shōhō and badly damaged Shōkaku. In ship losses the exchange favored Japan, but the planned seaborne assault on Port Moresby was cancelled.

American communications intelligence identified Midway as the principal Japanese objective and allowed Admiral Chester Nimitz to position three carriers northeast of the atoll before the Japanese striking force arrived. On 4 June U.S. carrier aircraft fatally damaged Akagi, Kaga and Sōryū in the late morning and Hiryū later in the day; all four Japanese fleet carriers were lost.

Japanese forces landed on the north coast of Papua in July 1942 and advanced across the Owen Stanley Range toward Port Moresby while Allied forces fought to hold the approaches from the south. Terrain, disease and the difficulty of moving food, ammunition and medical support through mountains and jungle shaped the campaign as directly as battlefield strength.

U.S. Marines landed on Guadalcanal on 7 August 1942 and seized the unfinished airfield that became Henderson Field. Japan repeatedly tried to reinforce the island and suppress the airfield by sea and air, turning the campaign into six months of connected land fighting, carrier actions, night surface battles and contested supply runs.

The assault on Betio at Tarawa began on 20 November 1943. Many landing craft could not cross the reef at the expected water depth, forcing Marines to wade several hundred yards under Japanese fire while amphibious tractors carried the first waves farther inshore. The island was secured after three days at a cost of roughly a thousand American dead.

U.S. forces landed on Saipan on 15 June 1944, beginning the campaign for the Marianas. Possession of Saipan, Tinian and Guam would put bases for B-29 operations within range of the Japanese home islands and breach an inner defensive line that Japanese naval planning considered important enough to justify a major fleet battle.

The return to the Philippines brought the principal surviving Japanese fleet forces toward Leyte in a multi-axis attempt to destroy the invasion shipping. From 23 to 26 October the battle unfolded through submarine attacks, the Sibuyan Sea, Surigao Strait, the action off Samar and Cape Engaño. Surigao Strait became the last battleship-versus-battleship action in naval history.

B-29 attacks from the Marianas began against Tokyo in November 1944 while submarines continued to destroy shipping and B-29 mines increasingly closed Japanese ports and sea routes. The bombing campaign shifted toward low-level incendiary area attacks in 1945; the raid on Tokyo during the night of 9–10 March killed an estimated 80,000 to 100,000 people.

U.S. Marines landed on Iwo Jima on 19 February against a Japanese defense organized in depth through caves, tunnels and fortified positions rather than a decisive defense at the waterline. The thirty-six-day battle produced more than 26,000 American casualties, including about 6,800 dead; of roughly 20,000 Japanese defenders, only 1,083 survived.

The U.S. Tenth Army landed on Okinawa on 1 April 1945 and encountered the main Japanese defense farther south around successive fortified lines, culminating at Shuri. American casualties reached 49,151, including 12,520 killed or missing. More than 100,000 Japanese military personnel were killed, and Okinawan civilian deaths also reached into the tens of thousands; exact civilian totals vary substantially by definition and source.