Why did Chongqing become the capital of Nationalist China in 1938?

Chongqing became the capital of the Nationalist government in 1938 primarily as a strategic retreat during the Second Sino-Japanese War.1

Following the outbreak of full-scale hostilities in 1937, Japanese forces captured Nanjing in December of that year. The Nationalist government, led by Chiang Kai-shek, initially moved to Hankou but was forced to relocate further inland to Chongqing in Sichuan province after Japanese military campaigns successfully occupied the Wuhan cities in 1938.23

This move allowed the government to establish a more secure base in the interior of central China, far from the immediate reach of Japanese coastal advances. The relocation involved moving hundreds of government offices, diplomatic missions, and significant industrial and educational resources from the coastal provinces to support the ongoing war effort. Despite persistent Japanese aerial bombings, the city served as the Nationalist capital until 1946, when the government returned to Nanjing.12