Before the Japanese attacked the US naval base in Pearl Harbour on 7 Dec 1941, which forced the US to action, China fought the Japanese alone from 1931 to 1941.
It was a lop-sided war. The Japanese has the airplanes, the tanks, the battleships, and superior weapons.
The western powers and the US watch from their foreign quarters, while the civilians in Shanghai and other cities were bombed ceaselessly.
A statement by a KMT Chinese officer to an American Bea Liu in Chungking is revealing.
He told her a plane circling Chungking was American. She insists it was Japanese. He replies ” But it couldn’t be up there without your country’s gasoline”.
(p 108 War in the Far East by Peter Harmsen, p 115 Liu Bea Exner Remembering China 1935-1945).
Chiang Kai Shek and Mao only have superiority in terms of numbers of soldiers.
An excellent book on the war on Chinese civilians is the memoir by Han Su Yin Destination Chungking.
This is her first book, before she started on her multi-volume memoirs.
She gave us a devastating account of the sufferings of the civilians in the 4-year war with Japan as she and her husband join the millions of civilians fleeing the Japanese invaders to seek sanctuary in Chungking.