When the "German" tank attacks the "V" shaped main gun support (used only when moving long distances and never in combat), it is clearly visible. A few seconds later, the support is missing. A second later, it is back in place.
The weather is too perfect for a movie about the Battle of the Bulge. In reality, the Germans attacked when they did because the Allies could not provide air support due to a weather system that brought dense clouds, fog and heavy snow to the area for days. But in this film there is no snow (not even on the ground) and any clouds are high, thin clouds that would not have prevented Allied planes from supporting the ground troops. The same problem is present in Battle of the Bulge (1965).
Both Lt. Col. Bartlett and Capt. Cooney are referred to as Company Commanders. This is redundant, as Cooney is Bartlett's subordinate and they both cannot have the same title. Bartlett's rank would suggest that he is actually the Battalion Commander.
The German tanks don't resemble any Panzers in use during World War II.
One of the German "tanks" is comically small. When Costa drops a grenade down the hatch, the tank appears to be equally as high as his shoulder, and while he lays on the deck it's apparent the tank is only about five feet wide. These tanks are perhaps 3/5 scale of any real WWII German tank and comically
crudely detailed.
Buddy Ebsen is listed as "Sfc. Tolliver - Fox Co.", with Sfc. as in Sergeant First Class. This rank was not established until 1948, changing the rank of 2nd Grade Technical Sergeant to Sergeant First Class.
In every shot in which they appear, the "German" tanks have external travel locks on their main gun, including whilst they are firing. These braces are mainly applied when the tank is being transported by ship or train, and is to prevent the turret from shaking and damaging sensitive systems like aiming mechanisms. However, any such device would be removed long before the tank enters combat, as it makes aiming virtually impossible. That, and thanks to recoil, the act of firing the gun in such a situation would not only damage the lock, but also likely harm the very mechanisms the lock is supposed to help protect in the first place.
When the wooden beam falls on Bernstein, breaking his leg, he twitches and the beam moves up, making it obvious that it's a prop weighing hardly anything.
The Germans are seen using a water cooled machine gun. While it is possible that they were using a captured machine gun, it is very unlikely, since nearly every army unit used air cooled machine guns.
In the last 10 minutes of the movie, a character is shot by several other characters.
With each of these shots, an empty shell casing should have been ejected from the rifles (M1 carbine and M1). In addition, the empty brass would have made a noticeable "tink" sound as it hit the stone floor in the cellar.
As Tolliver looks around after the sniper's first shot, the sniper inexplicably stands up and clearly exposes his entire body to the soldiers he shot at seconds earlier. The whole purpose of a sniper is to shoot from a concealed position.
The German machine gunners are seen from behind, with their upper bodies and their machine gun entirely above their sandbags, and the Americans are seen proceeding down the hill are in the background. The German machine gunners in this position would have been clearly visible to the Americans even as they began down the hill toward the village. Likewise, the German sniper in the bombed out bell tower is standing with his entire body exposed in a window opening, with the sky at his back. He would be impossible not to see at that range, and easy to shoot.
Buddy Ebsen was 48 years old when this movie was released, preposterously old for a combat soldier.
As Costa, Tolliver and Abramowitz start down the hill toward the town, Tolliver tells Abramowitz to move off further, so they're about ten feet apart. As they near the midpoint just before the start running, the three men are bunched up nearly close enough to hold hands, defeating the whole elaborate spreading out exercise they're loudly conducting.
Costa plunks Abramowitz down with a view out the window toward the Germans, telling him to keep watch, and Abramowitz immediately removes his helmet, which would be never more needed or useful to have on one's head than at this moment.