In the opening scene, which takes place in November 1918, the Sergeant shows another soldier the shoulder insignia he has designed and says it represents the "1st Infantry Dvision." The 1st Division was not called the 1st Infantry Division until May 1942.
Scenes set in Sicily show a modern Italian tricolor adopted for the Republic of Italy in 1948. During the war the flag would have been the Kingdom of Italy flag with the same tricolor but a House of Savoy emblem in the white field.
When Pvt. Zab is talking to a fellow soldier who is reading the book "The Dark Deadline" they both drink from a triangular-shaped Grants whiskey bottle. Grants didn't sell triangular-shaped whiskey bottles until 1957.
In the ambush scene, with the German hiding behind the cross, the sun is shining on the cross and the German's face. However, in the same sequence the cross casts a shadow across the field in the opposite direction to the first scene.
When Lee Marvin throws a grenade at the first machine gun nest, it leaves his hand and one of the machine gunners is moving like the grenade has already hit the nest. Then, it hits the nest and there is an explosion and the other two soldiers go into their dying throes.
During the WW1 scene between the Sergeant and the officer in the dug-out, the Sergeant learns that the armistice had been signed 4 hours previously at 1100hrs, November 11, 1918. While talking with the officer, the sergeant is cutting a piece of red cloth in the shape of a number '1' which he says he will submit as a proposed insignia for the division. However the shoulder sleeve insignia for the 1st Division consisting of a red number "1" was already approved on 31 Oct 1918.
The German Tiger tanks in this movie are actually Israeli M51HV
tanks modified from American-built M4A1 Shermans. The Israeli tank crewmen are wearing modern tanker helmets with microphones. In the one winter scene from the reconstructed version the German tank is an Israeli M50 converted from an M4 Sherman and here the tank commander is in a German uniform.
1st Infantry Division on 11th November 1918 held the line along Meuse river, near the town Mouzon (that were the final stages of Meuse-Argonne offensive, and whole war altogether); in the movie, when sergeant and his team approach an ambush by the old cross, we see that this is the spot from the first scene, the last day of the WWI. And on the memorial ("But the names are the same...") it reads "Killed in action - Soissons". Big Red One actually did fight near Soissons, but that was during the so-called Second Battle of the Marne, July to first week of August 1918.
During the combat in Africa at one point at least one German is seen wearing 'Flecktarn' pattern camouflage. Though spread through German units in Europe, particularly the SS, the pattern was never issued to members of the Afrika Korps.
When the sergeant and his unit are in Sicily, they walk in front of a wall with the portrait of Mussolini and a sentence in big capital letters written in Italian. The writing is incorrect. It reads "Se avanzo, Se guitmi! Se indietreggio, uccidetemi! Se muoiu, vendicatemi! Mussolini". It should be "Se avanzo, Seguitemi! Se indietreggio, uccidetemi! Se muoio, vendicatemi! Mussolini". It means "If I move forward, follow me! If I move back, kill me! If I die, avenge me!"
In the crematorium scene Griff doesn't fire 18 rounds as often thought. He fires 8, then if you listen closely, the ninth noise is a clip ejected, and the tenth is the sound of a new clip being inserted. He then fires another 8, which is correct.
During the battle at the cross the Sergeant is firing the tank machine gun. From the front the restricter, a metal plug with a small hole in it used to permit machine guns to fire blanks, is clearly visible in the muzzle.