Why did factories and people move from coastal China to Sichuan during the Sino-Japanese War?

During the Sino-Japanese War (1937–1945), factories and people moved from coastal China to Sichuan primarily because of the province's geographic isolation and inaccessibility, which made it an easily defensible bastion against Japanese forces.1

Because of these natural barriers, the Japanese military was never able to penetrate the region, allowing Sichuan to serve as a secure base for the Nationalist government, which established its seat in Chongqing from 1938 to 1945. This strategic relocation of industry and population, combined with the province's large population and economic self-sufficiency, facilitated extensive economic development and the establishment of new industrial centers in cities such as Chongqing and Chengdu.1