Blooper

During the attack on the dam, the saboteurs are repeatedly shown in daytime (albeit through a filter to make it appear darker than it was when filmed), but the soldiers patrolling on top of the dam are shown in true darkness at night.

By 1944 the camouflage of all German vehicles ( both SS and Wehrmacht) was changed from Dark Grey to Dark Yellow (with or with out Dark Green and Dark Brown patterns). During the whole movie all the vehicles are painted Dark Gray. Also the SS insignia was never painted on the doors of the vehicles especially in a circle. If some insignia was painted on the vehicle doors , that would have been the German Cross.

When the German Major and German Captain enter the radio room after the raid on the village, the radioman 'corpse' in the chair clearly takes several quick controlled breaths by breathing with his abdomen, then visibly swallows, right before he starts holding his breath. He is immediately knocked out of his chair and out of frame off screen by the Captain, probably to prevent more visible breathing from a corpse on the film.

After the German Captain kills the German Major, the Major is laying on the floor dead but his abdomen is clearly moving as he breathes.

Although the story takes place in 1944, all the hair styles are strictly in the 1970 mode. Hudson's fashionably long hair is strictly unmilitary, and he even sports 1970 sideburns and a handlebar moustache; Koscina's big hair is a 1970s trademark; even the kids look like refugees from the streets of the era in which the film was made, not at all like World War II orphans.

Whan Roc Hudson and the children raid the village, they mount an SS truck which also bears a (fictional) Panzer Division symbol. This could never be the case in real life.