In writing the script, Mankiewicz received uncredited input from CIA officer Edward Lansdale, who was often said to have been Greene’s inspiration for the American character he had called "Pyle" in the novel.

According to Greene, the inspiration for the character of Pyle was Leo Hochstetter, an American serving as public affairs director for the Economic Aid Mission in Indochina who was assumed by the French to “belong to the CIA”; they had lectured him during the “long drive back to Saigon on the necessity of finding a ‘third force in Vietnam.’”[5] The film stirred up controversy.

By promising marriage, he steals away a young Vietnamese woman (Giorgia Moll) from an embittered and cynical English newspaperman (Michael Redgrave), who retaliates by spreading the word that the American is actually covertly selling arms to the anti-Communists.

[4] In addition, filming was interrupted when Audie Murphy fell ill with appendicitis during a weekend shopping trip to Hong Kong and had to have emergency surgery.

[10] It was reported that Humphrey Bogart had been considered for the lead role; in fact it was offered to Montgomery Clift, with Laurence Olivier set to play "Fowler".

In The New York Times, Bosley Crowther wrote: "Scenes shot in the streets of Saigon have a vivid documentary quality and, indeed, the whole film has an aroma of genuine friction in the seething Orient.