Director Gillo Pontecorvo and composer Ennio Morricone had regular disagreements over the movie's score. At one point, Pontecorvo had a melody stuck in his mind which he desperately wanted as a theme in the movie. He went to Morricone's apartment to play it for him, and hummed the tune all the way up to the top floor. Then Morricone asked him to wait with the tune, since he had conceived a melody of his own. To Pontecorvo's surprise, the tune was exactly the same as the one he had in mind, and he was delighted to find out that after all those months of struggling, they had finally found something, separate from each other, on which they could agree. It wasn't until months later at the Venice film festival that Morricone admitted that he had pulled a prank on him; he had already heard Pontecorvo humming the song while coming up the stairs, and decided to pretend he had come up with the same melody himself.
In 2003, the New York Times reported that the Pentagon screened this film for officers and civilian experts who were discussing the challenges faced by the US military forces in Iraq. The flier inviting guests to the screening read: "How to win a battle against terrorism and lose the war of ideas".
The movie is famous for using almost only non-professional actors, who were chosen primarily for their resemblance to the people they play, acting skills being secondary. Director Gillo Pontecorvo got the performances he wanted from them by careful lighting, adequate staging and skillful directing.
Although the mass scenes look spontaneous, it took quite some planning to make them look that way. Director Gillo Pontecorvo would often draw chalk lines on the ground, dividing the mass in separate groups which had to start walking on cue in order to get proper crowd movement. He also used multiple cameras at a time and used footage from different angles to create the impression that crowds were much larger than they were in reality.
According to French government figures, there were 236,000 Algerian Muslims serving in the French Army in 1962 (four times more than in the FLN), either in regular units (Spahis and Tirailleurs) or as irregulars (harkis and moghaznis). Some estimates suggest that, with their families, the indigenous Muslim loyalists may have numbered as many as 1 million. They are not portrayed in this film.
The character of Col. Matthieu is loosely based on the real life General Jacques Massu. Right-wing elements in the French Army, led by General Massu seized power in Algiers and threatened to conduct an assault on Paris, involving paratroopers and armored forces based at Rambouillet, unless Charles de Gaulle was placed in charge of the Republic of France.
The only professional actor in the film is Jean Martin as Coloniel Matthieu. Director Gillo Pontecorvo wanted at least one professional actor, particularly in that pivotal role. The two argued frequently on set as Pontecorvo was trying to reign in Martin so that his performance would lie better with those of the non-professionals.