In the WW2 Pacific Theater of Operations, Japan had achieved full mastery of the seas and skies by April 1942, expanding eastwards and southwards. The Japanese government looked for raw materials for its industry and population. In 1937 Japan had invaded China. To sanction the Japanese Empire, the United States began an oil embargo against Japan in the Summer of 1941 to put pressure on this country, which had also made an incursion into French Indochina. These economic sanctions forced Japan to expand the border of its hegemonic empire to
to acquire the much needed natural resources for its industry and population.
In order to have a free way for its unrelenting expansion in Asia and in the Pacific, Japan carefully planned a powerful surprise military strike on Pearl Harbor to permanently damage and cripple the US Pacific fleet. Thus, on December 7, 1941, a Japanese carrier fleet launched a preemptive and powerful attack on Pearl Harbor, Hawaii. During the raid two US battleships were sunk and six fatally damaged. However, the Imperial Japanese Navy failed to find any US aircraft carriers and did not damage Pearl Harbor's usefulness as a naval base.
The Japanese attack united public opinion in the United States against Japan. The next day, December 8, the United States declared war on Japan. And Germany declared war on the United States on December 11. Hitler expected that Japan would support Germany by attacking the Soviet Union opening a new front for the Soviets. Japan did not oblige. This diplomatic move was a big mistake, for declaring the war on the United States unified the American public's support for the war.
In March 1942, the US Joint Chiefs of Staff divided the Pacific Theater into three areas of naval operation: the Southwest Pacific Area (under MacArthur), the Southeast Pacific Area, and the Pacific Ocean Areas (under Chester Nimitz). By April, 1942, Japan had completed the invasion of the Philippines and the British colonies of Hong Kong, Malaya, Borneo, and Burma, with the intention of seizing of the oil fields of the Dutch East Indies. The Japanese also obtained more victories in the South China Sea, Java Sea and Indian Ocean, bombing the Allied naval base at Darwin, Australia. In a matter of months, all these territories capitulated to the Japanese as thousands of British, American, and Indian forces surrendered to the invading army.
In April, 1942, Major General James Doolittle conducted an air raid on Tokyo, dropping bombs in industrial areas. Although Doolittle Raid was a small operation that did little actual damage, it boosted morale in the US, causing Japan to shift resources to homeland defense.
In May, 1942, Japan began operations to capture Port Moresby to sever the line of communications between the United States and Australia. Nevertheless Allies intercepted and threw back the Japanese naval forces at the Battle of the Coral Sea. Japan's next plan was to take Midway Atoll and lure the American carriers into battle to definitely eliminate it. In early June, Japan put their operations into action but the Americans broke Japanese naval codes in late May, and were fully aware of the plans and force dispositions. Using this knowledge, the US Navy achieved a decisive victory over the Imperial Japanese Navy at the Battle of Midway on June 5, 1942, sinking four Japanese aircraft carrier.
After American and Australian troops took back the occupied parts of the Solomon Islands (Guadalcanal), New Guinea, and the Dutch East Indies, the US Marines landed on the beaches of Betio island, Tarawa Atoll, on November 20, 1943, winning the Battle of Tarawa, which was the first heavily opposed amphibious assault in the Pacific theater. The American offensive continued in the southwest Pacific with the capture of the Marshall Islands before the end of February, 1944. The next American objective was the Mariana Islands, especially Saipan and Guam, in which the Japanese were strongly entrenched. But, by July 9, 1944, after a month of heavy fighting, Saipan was taken. With these islands in the Allied hands, Tokyo was within range of the American bombers.
In order to thwart the American invasion of Saipan and Guam, the Japanese committed much of their declining naval strength in the Battle of the Philippine Sea but suffered heavy losses in both ships and aircraft, with more than 600 Japanese aircraft wiped out of the sky and two carriers being sunk.
Then the American forces landed on the Philippine island of Luzon in January 1945, and Mindanao in March. Meanwhile, British, American and Chinese forces obtained a victory over the Imperial Japanese Army in Burma from October to March, then the British pushed on to Rangoon by May 3, 1945. American forces also moved toward Japan, taking Iwo Jima by March 26, and Okinawa by June. American B-29 bombed Tokyo and other Japanese cities as American submarines cut off Japanese imports.
Finally, on August 15, 1945, the Japanese Emperor, Hirohito, announced by Tokyo public radio the surrender of Japan, which was formally signed on September 2, 1945.
Below, photo of the Battle of Tarawa, the most vicious military engagement in the island-hopping campaign in the Pacific Theater.
