Factually completely wrong. Tactically completely wrong. Shot in the wrong weather and geography. In point of fact, the movie story line has almost nothing to do with the actual battle of the bulge. Movie ends with Germans abandoning their tanks and walking home, for lack of fuel.
Resembled the actual Battle of the Bulge about as much as an episode of Rat Patrol.
Perhaps the only factual scene in the movie. On 24 December, Kampfgruppe Peiper abandoned their vehicles in the forest near La Gleize and the 800 survivors walked back to German lines near Stavelot. The Spanish countryside that was used for the film might have worked pretty well for Rat Patrol. Bad, bad movie.