Plot hole: Alain joins the Legion, goes through extensive training and eventually gets his photograph taken. That's how Galgani recognises him and sends two men to kill him. They arrive with a platoon at the fort just after Alain, Mackintosh and Luther. The photograph would have taken a while to get back to France and then the two men would have to go through the same training. So how do they both end up in the same fortress after they joined the legion long after Alain?
Continuity mistake: During the ambush at the waterhole, the Arabs steal the Legionnaires' supplies by leading away the donkeys upon which the supplies were mounted. Why didn't the Legionnaires shoot the donkeys? Without them to carry the supplies the Arabs wouldn't have been able to take all before they withdrew.
Continuity mistake: When Alain and the big German Legionnaire are fighting in the barracks, the German throws him down upon a wooden table, smashing it and the nearby bench to pieces. The very next shot shows the German grabbing up the magically restored bench with both hands as he prepares to slam it down on Alain's head.