Reports say East Germany's secret police Stasi's propaganda film made in 1977 shows children as young as five being made to simulate war games.
The film was found in the Birthler Archive, the repository of the remaining files and documents of the Stasi, which was shut down at the same time as the East German state 20 years ago.
The black and white footage entitled "The Sun Always Lives" shows boys fighting with live ammunition as shells and smoke bombs explode around them.
The film features members of the Communist party's Young Pioneer youth movement and was filmed at one of their summer camps in the resort of Lubmin am Greifswalder Bodden, The Telegraph reports.
The film lasts for 21 minutes with the young participants mimicking the military manoeuvres of the People's Army of East Germany.
At the end of the film a live shell from one of the mini-tanks hits a wall. At this point the voice-over for the film says: "Show your soldierly face for the Socialist Fatherland as these brave warriors do!".
The children who took part in the films were often recruited into the agency and groomed for high political office, The Telegraph reports.