Battle of the Oued Mouilah

The Battle of the Oued Mouilah marked rupture of peace between France and Abd el-Kader. Colonel Combes attempted to join an isolated convoy near Sidi-Bel-Abbès when attacked by superior force led by Abd el-Kader in person. Trapped in a narrow valley, the French were encircled, suffered heavy losses, and had to retreat. This battle is considered one of the emir's first major military successes after end of the truce.

The Treaty of Tafna (1837) had left fragile peace between Abd el-Kader and French authorities, but French incursions outside their zone of influence—notably breaching the Iron Gates pass by the Duke of Orléans—were seen as provocation by the emir. On 15 October 1839 he declared war. The Battle of the Oued Mouilah occurred in this context of immediate escalation, during French attempt to secure a line of communication.

Abd el-Kader used numerical superiority and perfect knowledge of terrain. He drew French troops into narrow defile where light Algerian cavalry maneuvered rapidly to take them in reverse. Colonel Combes attempted to form defensive square, but topography made maneuver ineffective. French artillery, difficult to position, was quickly neutralized. Under pressure the French withdrew in disorder toward Tlemcen.

This defeat brutally relaunched war between France and Emir Abd el-Kader. It provoked massive military redeployment in western Algeria and strategic revision of French commands. For the emir, victory reinforced his prestige among tribes and allowed him to rally new support. The battle demonstrated once again difficulty of conducting effective campaigns against an adversary mastering terrain and art of mobile warfare perfectly.