During the German occupationm Emile-Georges De Meyst wrote for the underground press, and in July 1944 he came up with the idea of shooting in secret a fiction film about the Resistance. By pretending to make cultural documentaries he built up a stockpile of film and he and René Herdé (who was to play the leader of the network) then concocted a script about the evil deeds of drug traffickers. Caution was indeed called for, since the sound engineer turned out to be an infamous collaborator. Shooting began during the final weeks of the Occupation with most actors believing they were playing in a crime movie. The Liberation of Brussels afforded the opportunity to shoot the uniformed sequences and De Meyst rapidly completed what was to be the first feature film on the Resistance.