The heist sequence lasts for exactly 27 minutes and features no dialogue at all.
The Opening Credits show a quote that explains the title of the film. The epigraph, credited to Buddha, was in fact written by director Jean-Pierre Melville. He also wrote the epigraph in O Samurai (1967), credited to the Book of Bushido.
From the beginning of filming, there was great tension between director Jean-Pierre Melville and Italian actor Gian Maria Volontè, who plays the fugitive Vogel in the film (a role originally written for Jean-Paul Belmondo). Volonté, an intense and politically committed actor, disliked Melville's affectations and resented his perfectionism, particularly his constant fussing with Volonté's costume, so that he would have exactly the right "look" for the film (though the filmmaker did the same thing with stars Alain Delon and Yves Montand). Volonté eventually became so angry with Melville that he left the set for two days and had to be persuaded by Delon to return. It was only twenty years later, long after the director's death, that Volonté admitted to the writer Rui Nogueira, who had published a book of interviews with the director, that he had come to appreciate Melville as a great filmmaker.
One month before the film's premiere Bourvil (Mattei) passed away (Kahler's disease). He was about to play a part in Mania de Grandeza (1971) which then instead was played by Yves Montand (Jansen).
Director Jean-Pierre Melville's green Ford Mustang can be seen in the line of cars at Corey's (Alain Delon) first border crossing.