During the final days of world war one, a German army deserter steals the identity of a dead German soldier. His new name is Otto Josef Klems. After the war, he joins the French Foreign Legion as Sergeant Otto Josef Klems. The year 1924 finds him in a French Foreign Legion garrison in French Morocco. Two European powers, France and Spain, control colonial Morocco. However, both colonial powers face strong rebellions from the local Moroccan tribes that unite in order to defeat the European armies and achieve independence for Morocco. During the course of his duties in Morocco, Sergeant Klems runs afoul of a new brutal commanding officer, a Captain. Disgusted by his Captain's behavior and by the treatment of locals at the hands of the French troops, Sergeant Klems decides to desert. It seems that others, too, had the same idea, since many native troops desert the French garrison at night. On such a night, Sergeant Klems is on duty and surprises a group of French soldiers of native origin, desert to the enemy. Klems refuses to shoot the escaping deserters, due to his personal friendship with some of them. Unfortunately, his Captain finds out about Klems' refusal to shoot the deserting soldiers and court-martials Klems. Found guilty, Klems is condemned to prison but he escapes from the garrison's jail-cell and deserts. Wondering in the desert, he collapses in the heat and without water or food. He is found by a passing Bedouin who takes Klems prisoner and sells him to the rebel army of rebel Moroccan leader Mohamed Abdel Krim. At the rebel stronghold, Klems is about to be executed by the rebels when he witnesses an accident. A group of rebels attempt to load a captured French howitzer with the wrong caliber ammunition. While hammering the round into the gun's barrel, the round explodes killing many rebels. Klems intervenes and saves the life of a beautiful Moroccan woman who happened by. She turns out to be the sister of the rebel leader. Klems tries to tell the rebels they cannot load a gun with the wrong type of shell but the rebels, who only speak Arabic, dismiss him. At that moment, the rebel leader Mohamed Abdel Krim, who speaks a few European languages, notices the incident. He allows Klems to explain the correct procedure of loading and firing an artillery piece to the curious rebels. Sensing an opportunity to save his own life, Klems offers to teach the rebels how to properly use captured enemy artillery pieces. But he also has another reason to want to stay alive. He wants to meet the beautiful woman whose life he just saved. Eventually, the rebel leader Mohamed Abdel Krim allows Klems to join his rebel army and to meet his sister. However, a small rebel army of natives has little chance in defeating the combined armies of several European powers that are determined to end the rebellion by any modern military means necessary.