Lots of authentic footage from the Continuity War were used in the film. Editors Osmo Harkimo and Armas Vallasvuo edited this footage together with the non-authentic footage and they did their job so skillfully that in some scene it is almost impossible to say whether the footage is authentic or not.
Åke Lindman was so fed up with playing villains and bad guys that he would have liked to play Koskela, who was the most rightful character in the film. But he ended up playing Lehto, the bad guy of the movie. In spite of his dis-likeness of the character, Lindman was awarded with Jussi-Prize for the role.
Right after Väinö Linna had published his novel Tuntematon sotilas, Mauno Mäkelä, the manager of Fennada-Filmi made a tentative reservation of the filming rights. But Edvin Laine, who was working for SF (Suomen Filmiteollisuus) at the time, read the novel and immediately traveled from Helsinki to Tampere to meet Väinö Linna to invalidate Mäkelä's reservations. Laine believed so much in the novel that he promised Linna more money for the filming rights than Mäkelä, although he didn't have the authorization to do so. In spite of this ruthless act Mäkelä and Laine later made two films together Täällä Pohjantähden alla (1968) and Akseli ja Elina (1970). These films were based on Väinö Linnas Täällä Pohjantähden alla-trilogy.
The production of the film started so late in the early of 1955 that the snow that was needed for the Winter-sequences had already started to meld. That's why screenwriter Juha Nevalainen wrote these sequences first that they could be filmed, before the snow was gone.
In the book, sergeant Hietanen destroys a Soviet KV-1 tank. However, the film makers could not get that tank type for this production and not even some other Soviet tank despite that Finnish Army did have some T-34s and thus the tank in the film is a German Panzer IV.