The film depicts an episode in the war of independence in then-French Algeria, in the capital city of Algiers. It reconstructs the events of November 1954 to December 1960 in Algiers during the Algerian War of Independence, beginning with the organization of revolutionary cells in the Casbah. From there, it depicts the conflict between native Algerians and European settlers (pied-noirs) in which the two sides exchange acts of increasing violence, leading to the introduction of French paratroopers, under the direction of General Massu and then Colonel Bigeard, to root out the National Liberation Front (FLN). The paratroopers are depicted as "winning" the battle by neutralizing the whole FLN leadership through assassination or capture. However, the film ends with a coda, depicting demonstrations and rioting by native Algerians for independence, in which it is suggested that though the French have won the Battle of Algiers, they have lost the war.
The narrative is composed mostly of illustrations of the tactics of both the FLN insurgency and the French counter insurgency, as well as the uglier incidents in the national liberation struggle. It unflinchingly shows atrocities being committed by both sides against civilians. The FLN is shown taking over the Casbah through summary execution of native Algerian criminals and others considered traitors, as well as using terrorism to harass civilian French colonials. The French colonialists are shown using lynch mobs and indiscriminate violence against natives. Paratroops are shown employing torture, intimidation and murder to combat the FLN and Algerian National Movement (MNA) insurgents.
Refraining from the conventions of the historical epic, Pontecorvo and Solinas chose not to have a protagonist but several characters based on figures in the conflict. The film begins and ends from the point of view of Ali la Pointe, played by Brahim Hagiag, who corresponds to the historical figure of the same name. He is a criminal radicalized while in prison and is recruited to the FLN by military commander El-hadi Jafar, a fictional version of Saadi Yacef played by himself.
Other characters include the young boy Petit Omar, a street urchin who serves as a messenger for the FLN; Larbi Ben M'hidi, one of the top leaders of the FLN, who is used in the film mainly to give the political rationale for the insurgency; Djamila, Zohra and Hassiba, a trio of female FLN militants called to carry out a revenge attack. In addition, The Battle of Algiers used thousands of Algerian extras in bit parts and crowd shots; the effect Pontecorvo intended was to create the impression of the Casbah's residents as a "chorus," communicating to the viewer through chanting, wailing and physical effect.
The Algerian revolution has been called by many the bloodiest revolution in history. Although the revolutionary forces in Algiers were defeated by the French Army, the long war throughout the country led to the French withdrawal from Algeria. The theme of showing the inevitable demise of colonialism as an instrument of Western imperialism was central to Pontecorvo and Solinas's treatment of The Battle of Algiers.
In 2003, the film again made the news after the Directorate for Special Operations and Low-Intensity Conflict at The Pentagon offered a screening of the film on August 27, regarding it as a useful illustration of the problems faced in Iraq. A flyer for the screening read:
"How to win a battle against terrorism and lose the war of ideas. Children shoot soldiers at point-blank range. Women plant bombs in cafes. Soon the entire Arab population builds to a mad fervor. Sound familiar? The French have a plan. It succeeds tactically, but fails strategically. To understand why, come to a rare showing of this film."According to the Defense Department official in charge of the screening, "Showing the film offers historical insight into the conduct of French operations in Algeria, and was intended to prompt informative discussion of the challenges faced by the French."