Goofs

As Col. Dax walks past soldiers right before the attack, the same soldier with a pipe appears more than once.

After the court martial, as the sergeant is addressing the guards describing the procedure and discipline required of the firing squad, all of the guards in the rank have a "710" regiment number collar pin whereas the sergeant (and those in Col. Dax's regiment) have a "701". Although it might be a simple matter of the costuming department transposing the two numerals, the difference might also be intentional. If a firing squad is going to execute three men in a given regiment, then you'd want to have men from another regiment come in and do it to avoid having men shooting their friends.

Col. Dax's boots change positions after he kicks them off (1:02)

After Gen. Mireau slaps the soldier in the trench, he continues on to Col. Dax's dugout and three soldiers carrying a machine gun pass him. The same three soldiers still with the machine gun pass him again when he and Dax are looking at the Ant Hill through the binoculars.

The dueling scar on Gen. Paul Mireau's right cheek seems to change from light to dark in various scenes.

Just before the German girl sings, the soldiers begin to cheer and whistle enthusiastically. In Europe, unlike in the US, whistling is a way of showing displeasure, like booing. The whistling here might also be interpreted as a sign of such displeasure with the Germans, in general, the girl being a symbol of the enemy..

The infantry regiment number 701 did not exist because the French army never had more than 418 infantry regiments during the First World War.

The conduct of the court martial as described in the movie is inspired by Anglo-Saxon rather than French law. For example, there is never any "objection" during a trial in France.

General Broulard tells Colonel Dax that he would invite him to the party, but it is a formal dress affair, but General Broulard isn't in formal dress himself.

The general simply was making a transparent excuse that Dax was not welcome.

As Col. Dax is running through the trenches after Gen. Mireau gives his order, a "dead" soldier blinks.

In the bar at the movie's end, in order to look scruffy and disheveled, some of the men had obvious phony beards and mustaches glued onto their faces, some not very well. The reason? Those "soldiers" were actually off-duty Munich Policeman who were hired for the scene and HAD to be clean shaven for their "real" jobs.

At 55:27, a sergeant is clearly shown wearing "710" on his collar tabs, while all other soldiers wear "701." The regiment throughout the film is identified as the 701st, making this a likely costume error involving the incorrect unit number.

The French soldiers are shown using a British Vickers machine gun in one of the trench scenes. They should have been using a Hotchkiss weapon, or some other firearm of French design.

At the end of the film, when the German girl sings, there are modern (1950s) metal music stands on the stage.

Camera wire visible in few shots where the prisoners are being taken to their execution spot.

During an artillery explosion on the charge on No Man's Land, the large pipe that was buried to shoot debris for that explosion is clearly visible for a moment (to the left of Col. Dax).

During the first tracking with Dax in the trenches, the shadow of a boom mike is visible.

Col. Dax commits a glaring military faux pas by jamming his hands into his pants pockets while standing and walking in the courtroom during the trial. No military officer would do such a thing, particularly in such a formal setting as a court martial.

When preparing the three defendants for trial, Col. Dax tells them that he's seen the room where they'll be tried, and that the afternoon sun will be in their faces. In fact, the sun is at their backs.

During the night patrol, Lt. Roget sets his revolver down on the edge of the artillery crater and throws a hand grenade in the direction of Private Lejeune, then runs back to the trenches without picking up his revolver. Corporal Paris then proceeds forward toward Lejeune's position without picking up Roget's revolver.

The priest says "et spiritui sancti" instead of the correct "et spiritus sancti".