James Arness (Garby) served in World War II and is the most decorated of the actors in the film. He received the Bronze Star, the Purple Heart, the European-African-Middle Eastern Campaign Medal with three bronze campaign stars, the World War II Victory Medal, and the Combat Infantryman Badge for his service.
Douglas Fowley (Private Kippton, he of the continually lost false teeth) served in the Navy in the South Pacific in World War II, and lost all of his own teeth in an explosion aboard his aircraft carrier during battle.
The white "card suit" stencils on the sides of the soldier's helmets in the film are accurate. The World War II 101st Airborne Division used the different suits to identify their three parachute infantry (diamonds, hearts, and spades) and one glider infantry (clubs) regiments. A white "tic" at either the twelve, three, six or nine o'clock positions around the suit indicated Headquarters, 1st, 2nd, or 3rd Battalions, respectively. The soldiers in this film wear the club suit of the 101st's 327th Glider Infantry Regiment, with a "tic" at the nine o'clock position, indicating they belong to that regiment's 3rd Battalion.
Twenty veterans of the 101st Airborne, who fought in the Bastogne area, were hired to train the actors, and were also used as extras.
Screenwriter Robert Pirosh based this story on his experiences as an infantryman during the Battle of the Bulge. Pirosh did not serve with the 101st Airborne, and wanted to create a script that was faithful to their experiences. He used his first-hand knowledge of the battle to write the script. This was done with the blessing of General Anthony McAuliffe, who was commanding the 101st during the siege of Bastogne. Consequently, many of the incidents in the film, such as Private Kippton's habit of always losing his false teeth, or the Mexican-American soldier from Los Angeles, California, who had never seen snow until he got to Belgium, that have always been derided as "typical Hollywood phony baloney" actually happened.