Jean-Paul Belmondo performed all his own stunts, including an unprotected fall from a flight of stairs.
Filmed at the actual location of one of the operation Dynamo evacuations, on the beaches of Bray-Dunes near Dunkirk.
The scene where Maillat and Pinot confront two German paratroopers was filmed in the ruins of the Eglise de Notre-Dame in Calais. The war- damaged building was still not rebuilt by 1964.
This film's source novel "Weekend at Zuydcoote" by Robert Merle won the 1949 Prix Goncourt, a French literary award for "the best and most imaginative prose work of the year".
Robert Merle was not satisfied with the adaptation of his novel. He said that the warfare was too present in the film and his book character far more intellectual than Belmondo's performance.