Evacuations of civilians in Japan during World War II
About 8.5 million Japanese civilians were displaced from their homes between 1943 and 1945 as a result of air raids on Japan by the United States Army Air Forces (USAAF) during the Pacific War. These evacuations started in December 1943 as a voluntary government program to prepare the country's main cities for bombing raids by evacuating children, women and the elderly to rural towns.
Source: Wikipedia — Evacuations of civilians in Japan during World War II (CC BY-SA 4.0)