The film was based on a book published in 1939 by the same title. That book was written by Dalton Trumbo and won the National Book Ward that year. Remember this was pre-WWII and WWI was still the war-to-end-all-wars. I had heard of Trumbo as one of the Hollywood ten. They were writers who were blacklisted during the red scare by pressure from HUAC (House Un-American Activities Committee.) It was a witch hunt, which is broadly considered to be an unforgivably dark corner of American history.
WWII changed the government perception of Trumbo's anti-war book and he was blacklisted in 1947 after refusing to give HUAC any information. Hhe was imprisoned for contempt of Congress for 11 months then blacklisted. He lived in Mexico for over a decade writing under pseudonyms. The blacklist didn't end formally but dissipated in the post-McCarthy era and Trumbo was able to put his name on scripts again by 1960. But before the red scare hit the fan, back in March of 1940 Arch Oboler wrote a radio play based on the book. It was broadcast on NBC Radio as part of the series "Arch Oboler's Plays." I found the radio play on Youtube only today.