Factual error: Why is Hilts not wearing a uniform? A serving officer captured behind enemy lines in civilian clothing risked being shot as a spy. If a prisoner's uniform was too worn or damaged to wear, it was routine for the German authorities to replace it - a P.O.W. in civilian clothes is an obvious escape risk. He is wearing a pair of tan chinos and a cut off sloppy Joe sweatshirt, both ridiculously anachronistic - Sixties hipster fashions - and nowhere even close to a World War 2 uniform.
Audio problem: While Marcello Mastroianni is waiting at the station and Sandra Milo's train can be heard arriving off-screen, we hear much whistling by a steam train, but when it finally appears, the train is being hauled by a diesel locomotive. [As a side note/explanation - all sound in Italian movies, including the dialogue, is recorded afterwards, sometimes by different actors, eg. Claudia Cardinale in real life has a regional accent.]
Factual error: The weapons for this film, save for the American Krag-Jorgensen rifles, British Lee-Enfield MLE rifles, and German Mauser Gewehr 98 rifles, are completely wrong. The Russians, who had Mosin-Nagants, are portrayed with Mausers. The French are for the most part correctly poratrayed with Lebel Mle. 1886/93 rifles, but a few have Berthier rifles that weren't used until 1907. The Austro-Hungarians are portrayed with a mixture of Mausers and Berthiers when they would have had Mannlicher M88/90's or perhaps Mannlicher M95's. The Japanese are equipped with Mausers and would in reality have had Muratas. The Italians have a mix of Berthiers and Mausers, but would've used Vetterli-Vitali rifles. The Chinese Imperial troops and Boxers both have Gewehr 98 Mausers. Although they did indeed have Mausers, they had the far earlier Gewehr 71's and Gewehr 71/84's.