The film was and remains the most successful movie ever in Finland; about 2.8 million people, or more than half the Finnish population, saw it in theaters.

Set against the events of the Finnish Continuation War, the film follows a machine gun troop's journey into the Soviet Union.

The troop includes the simple-minded Hietanen, the jokey Vanhala, the cynical Lahtinen, the cowardly Riitaoja and grumpy Lehto.

They face many struggles, such as seeing the supportive Kaarna die in their first battle, three of the soldiers refusing to leave their punishment post during an air-raid as well as defending the trenches after the Finns have taken back parts of Karelia.

Part of the way, the troop is joined by Rokka, a Karelian veteran of the Winter War, who also clashes with Lammio due to having little respect for military discipline despite being an excellent and capable soldier.

His military ambulance crashes and the blinded Hietanen is gunned down by passing Russian planes while trying to save the other injured soldiers.

Reino Tolvanen was an actual veteran of the Continuation War, having served in the air force, and was cast due to speaking the dialect naturally.

Upon completion, The Unknown Soldier was the longest and most expensive film in the Finnish cinema history up to that point: 181 minutes and, according to the account book, FIM 46,667,761.