Co-writer/Director Claude Sautet said after the shooting that he did not know that the Abel Davos - Danos - character was inspired by a gangster who collaborated with the Nazis against French resistance and Jews during German occupation.
This film is inspired from actual events and character: Abel Danos, renamed Davos here, who was a gangster heavily involved in the French Gestapo in Paris, rue Lauriston, between 1941 and 1944. Writer José Giovanni, his real-life nephew forgets this and magnifies this character, as he will later do in other of his stories and novels. Commissioner Blot is based on the real life Commissioner Georges Clot.
The opening sequence was filmed in candid camera, which lead to passersby in Milan thinking they were witnessing an actual robbery and chasing the actors down.
This film is part of the Criterion Collection, spine #434.
Was released one week after À bout de souffle (1960), another film starring Jean-Paul Belmondo. That film's massive success was named as a reason for this one underperforming.