Factual error: Almost all the German soldiers in the movie are armed with MP-40 SMGs. In fact, most German infantrymen during World War II were armed with Mauser rifles. MP-40s were only issued to squad leaders and officers.
Continuity mistake: When Kelly visits Mulligan he is carrying a bottle of whiskey, he then visits crapgame who gives him a bottle of whiskey, which suggests that the scenes are the wrong way round and Kelly was originally meant to visit crapgame first.
Factual error: The sniper rifle used in the film is a Russian Mosin and were never used by the allies. They should have had a Springfield sniper rifle. The Americans would have had no occasion to "exchange" weapons with Russian soldiers until the end of the war, when they met on the Elbe River.
Continuity mistake: As the squad are taking a break on top of a hill, just before the fighter-bomber attacks them, Corporal Job is distributing ammo and Jonesey can be seen walking past in the background with four boxes of K-rations. A moment later, Crapgame and Jonesey are sitting together sharing the contents of the boxes. After Crapgame goes to the jeep for some water, the shot cuts to Kelly sitting by a tree. Jonesey walks up to Kelly with a message from Big Joe - carrying four unopened K-rations boxes.
Continuity mistake: When Kelly asks Little Joe for the brandy to interrogate the German officer, he is handed a square bottle with a short neck. In the next shot, as they sit down for their "friendly drink" Kelly sets down a round bottle with a long neck.
Factual error: As Oddball and his motley crew depart with the "purchased" Tiger, Moriarity is standing up in the hatch, fiddling with his cap. Since this is the driver's position, and very cramped, either he is straddling the driver's shoulders, or driving with his feet.
Factual error: Near the end of the movie the general and the army convoy drive through the town and are stopped by all the celebrating going on. If you look at all the cheering villagers, you can see they are dressed in modern (for 1970) clothes and have hairstyles that were not around in the 1940s.
Continuity mistake: Two of the German SS Tank officers are walking together through the streets of Clairmont chatting. In the first scene with them, the officer on the left carries the rank of 'Obersturmführer,' denoted by his lapel badges, and the officer on the right has lapel badges showing him to have the rank of 'Sturmbannführer' (although both officers' shoulder badges show no correlating rank to their lapels). However, in the second scene with the same two officers still walking and chatting, the officer on the right has been demoted as he is now showing the rank of 'Untersturmführer.'
Other mistake: When they are lifting the boxes of gold at the end of the movie you can tell that the boxes are empty.
Factual error: The "BAR" carried and fired in the movies is actually a FN-D Model that was never issued by the US Army in WWII. It was developed post war in Europe. Also the Thompson machine guns and the 1919A4s are all firing at a accelerated rate of fire, much faster than normal. This can be attributed to the weapons being blank adapted.
Continuity mistake: After Cowboy spots the Tiger coming down the street the scene changes to a view of the three soldiers running from away from the bank from the viewpoint of the Tiger. The Tiger's turret is facing the soldiers. In the next shot the Tiger is shown in the distance with its barrel pointing straight forward. In the next shot, the turret is facing the fleeing soldiers again.
Factual error: During the scene where Clint Eastwood is trying to convince Don Rickles to join in the heist, there is a box of Almond Joy candy bars behind Don's head. They weren't introduced until 1946.
Continuity mistake: At the end when confronting the last tank to get the bank doors open, Oddball, Big Joe, and Kelly line up in an alley as if they are directly facing the tank and start walking forward. In the next shot, which is wider and much farther away, you see that they are actually walking down a curved alley and can't see the tank until they come all the way around the corner.
Visible crew/equipment: Clint Eastwood drives his jeep up to Telly Savalas who asks where Eastwood has been. Shot changes to over Savalas' shoulder, and look at Eastwood. At the rear of the jeep, immediately behind Eastwood and in the middle of dozens of fatigue clad GIs, a crew member in a button-down striped shirt fiddles with something for a few seconds before glancing up at Savalas and then walking out of the frame.
Factual error: In the final shot of the movie, the Tiger tank/T34 is seen driving away emitting masses of diesel smoke common to the Russian T34. However the Tiger was a petrol tank, not a diesel, as mentioned by the German tank commander. The Sherman was also petrol and well known for its ability to catch fire when hit. It was nicknamed the 'Ronson.'
Continuity mistake: While big Joe is talking down to the Captain in the boat, Joe is blocking the stairs to the upper deck with his whole body. As the Captain moves up the stairs, Joe is off to the Captain's right. When the Captain emerges from the lower deck, Joe is dead center of the Captain and then moves out of the Captain's path.
Continuity mistake: Near the end of the film as Oddball's Sherman drives into the French town, the amount of ammunition in the ammo holder on the turret .50 calibre machine gun gets larger in almost every shot. As the tank crashes through the bushes approaching the town there is hardly any ammo in the box, up until the second Tiger is ambushed when suddenly there is plenty of ammunition.
Factual error: At the beginning of the film as the camera follows the security sergeant he taps a man on the shoulder. The man was standing next to the crossroads signs in a camouflage poncho. As he turns, you can see that he that he is wearing jeans and not a standard uniform of the era under the poncho.
Continuity mistake: When the last surviving Tiger rages in Clairmont, shooting at surrounding buildings, there are a couple of shots, when we see both the tank's gun firing and the 'shell impact' effect. The tank's gun is not always pointed at the exact spot where the 'shell' explodes - it's particularly visible when the Tiger lowers the gun and shoots a hole in a wall, immediately after Big Joe threw a grenade and fired at the tank with his SMG. The hole in the wall appears a good few feet to the left, from where the gun points and the actual projectile would hit.