Throughout the film's long development Luise Rainer, Margo, Maureen O'Hara, Kim Hunter, and Claudette Colbert were all considered for the female lead and Paul Henreid was considered for the male lead.
This film had a long and difficult gestation. RKO bought the rights to Pearl Buck's story in September of 1941. The screenplay went through many re-writes as in the original novel it was a Chinese doctor who collaborates with the Japanese for money and RKO studio executives objected to that. Finally, by March of 1944 the doctor's nationality had been changed to Japanese-Korean.
According to the date on the telegram Dr. Durand receives near the beginning of the film, this story starts in October of 1938.
According to film scholar Hye Seung Chung in her book "Hollywood Asian"; the character of Dr. Kim (played by Korean-American actor Philip Ahn), is notable as very first self-identifying Korean character in a Hollywood film.