During the Joseph McCarthy-inspired "Red Scare" era in the 1950s, this was one of the films labeled subversive by the HUAC (House Un-American Activities Committee) because it was alleged to have contained dialogue that might be construed as pro-communist. Writer John Wexley was even blacklisted. It wasn't seen again in the United States until the mid-1970s.
Originally, Bertolt Brecht was denied story credit by the Screen Writer's Guild, even though he worked closely with writer John Wexley on the project.
The original titles for the project were No Surrender, Never Surrender, Unconquered, We Killed Hitler's Hangman, Trust the People, and Lest We Forget. They had to choose a new title because a book was published with a similar title (No Surrender, Never Surrender) during production. Producers held a contest among the cast and crew to choose a new title. A production secretary submitted the winning title and won $100.
The assassination of Reinhard Heydrich has been the subject of at least five other films: HHhH (2017), Opération Anthropoid (2016), Opus Pro Smrtihlava (1984) (a documentary), Sept hommes à l'aube (1975) and Commando à Prague (1964), 1965. Heydrich also is the lead character in Conspiration (2001), in which he is played by Kenneth Branagh. And on American TV, there was a 2-part entry titled "Heydrich" on CBS's 30-minute Jack Webb-hosted anthology, G.E. True (1962). These shows premiered in May 1963.
Produced during World War II, the film's credits list Bertolt Brecht's distinctly German name as simply "Bert Brecht."