The Vice Chief of the Imperial Japanese Navy General Staff, Vice Admiral Takijirō Ōnishi, predicted up to 20 million Japanese deaths. Casualty predictions varied widely, but were extremely high. In all, there were 2.3 million Japanese Army troops prepared to defend the home islands, backed by a civilian militia of 28 million men and women. Most were immobile formations for coastal defense, but 16 were high quality mobile divisions. Four veteran divisions were withdrawn from the Kwantung Army in Manchuria in March 1945 to strengthen the forces in Japan, and 45 new divisions were activated between February and May 1945. The Japanese planned an all-out defense of Kyūshū, with little left in reserve for any subsequent defense operations. Japan's geography made this invasion plan obvious to the Japanese as well they were able to predict the Allied invasion plans accurately and thus adjust their defensive plan, Operation Ketsugō, accordingly. US Army poster prepares the public for the invasion of Japan after ending war on Germany and Italy The target date was chosen to allow for Olympic to complete its objectives, troops to be redeployed from Europe, and the Japanese winter to pass. Operation Olympic was to be followed in March 1946 by Operation Coronet, the capture of the Kantō Plain, near Tokyo on the Japanese island of Honshū by the US First, Eighth and Tenth Armies.
Set to begin in October 1945, Olympic involved a series of landings by the US Sixth Army intended to capture the southern third of the southernmost main Japanese island, Kyūshū. The operation had two parts: Operations Olympic and Coronet. Plans were underway for the largest operation of the Pacific War, Operation Downfall, the invasion of Japan, before the surrender of Nazi Germany on May 8, 1945. Along the way, the ratio of Japanese to American casualties dropped from 5 to 1 in the Philippines to 2 to 1 on Okinawa. In April 1945, American forces landed on Okinawa, where heavy fighting continued until June.
In order to free troops for use elsewhere, offensives were undertaken to reduce the Japanese forces remaining in Bougainville, New Guinea and the Philippines. The policy of bypassing Japanese forces was abandoned. In the Pacific during this period, the Allies returned to the Philippines, and invaded Borneo. December 1944 saw American battle casualties hit an all-time monthly high of 88,000 as a result of the German Ardennes Offensive. Of the 1.25 million battle casualties incurred by the United States in World War II, including both soldiers killed in action and wounded in action, nearly one million occurred in the twelve-month period from June 1944 to June 1945.
In 1945, the Pacific War between the Empire of Japan and the Allies of World War II had entered its fourth year. The bombings' role in Japan's surrender and their ethical justification are still debated. On August 15, six days after the bombing of Nagasaki, Japan announced its surrender to the Allies, signing the Instrument of Surrender on September 2, officially ending World War II. In both cities, most of the dead were civilians, although Hiroshima had a sizeable garrison. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness.
Within the first two to four months of the bombings, the acute effects killed 90,000–166,000 people in Hiroshima and 60,000–80,000 in Nagasaki, with roughly half of the deaths in each city occurring on the first day. A Little Boy atomic bomb was dropped on the city of Hiroshima on August 6, 1945, followed by a Fat Man bomb on the city of Nagasaki on August 9. The Japanese government ignored this ultimatum.īy August 1945, the Allied Manhattan Project had developed and tested atomic bombs, and the United States Army Air Forces 509th Composite Group was equipped with Silverplate Boeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. Together with the United Kingdom and the Republic of China, the United States called on Japan to surrender in the Potsdam Declaration on July 26, 1945, threatening "prompt and utter destruction". The war in Europe ended when Nazi Germany signed its instrument of surrender on May 8, 1945, but the Pacific War continued. The two events are the only use of nuclear weapons in war to date.įollowing a firebombing campaign that destroyed many Japanese cities, the Allies prepared for a costly invasion of Japan. The atomic bombings of the cities of Hiroshima and Nagasaki in Japan were conducted by the United States during the final stages of World War II in 1945.