In the Pacific, the war was no less brutal. Japan had expanded rapidly throughout southern Asia, taking all of Southeastern Asia and the Dutch East Indies. Two areas fell outside of Japanese control: India, still under British rule, and Australia. The bombing of Pearl Harbor brought the United States into the war, and the Pacific theater then became primarily a battle between Japanese forces and the United States. The United States employed a strategy known as “island-hopping,” moving strategically from island to island, retaking territory from Japan and trying to get closer to the Japanese archipelago. Progress was painfully slow. The Japanese composed a battle-tested and zealous fighting force and were at first better equipped for war, having been mobilized since the mid-1930s. As the war continued in the Pacific, the differences between the enormous industrial potential of the United States and the limited potential of the much smaller Japan became ever more acute. After the Battle of Midway, for example, during which Japan lost four of its largest six aircraft carriers (the key unit of Pacific power) Japan was unable to replace them. Gradually, as in Europe military capacity shifted starkly in the favor of the allies. Artillery, bombs, and machine-gun fire came raining down on the less-equipped Japanese. Island after island fell in bloody fighting, the Japanese, like the Germans, fighting for every inch of territory.

By 1945, the Japanese military forces were broken. Japan braced hopelessly for the pending American attack. It was at this moment that the new American President, Harry Truman, made his fateful decision to use a new secret weapon against the Japanese civilian population. The atomic bomb, developed in secrecy in the United States by a group led by physicist Robert Oppenheimer, was dropped first on August 6, 1945 on Hiroshima, killing around two hundred thousand people. Truman, in a public radio address announcing the bombing of Hiroshima, called the city a “military base.” Such was the confused and entangled morality of the Second World War. On August 14, 1945 Truman approved a second atomic bombing—this time on the city of Nagasaki. The bombings brought Japanese surrender, and in late August of 1945 the Second World War came to an end.