The story follows the East German Army's 666th TSF Squadron in its battles and political conflicts during the BETA's westward push in 1983.

The East German Army 666th TSF Squadron "Schwarzesmarken" (Black Marks) are a special-forces unit tasked with assaulting BETA forces through unconventional tactics; specifically, they target Lux and Magnus Lux to deny the BETA the advantage of ranged firepower. Their orders are given the topmost priority, such that it is common practice for the 666th to ignore allied distress calls that will result in deviation from their original mission, even if only for a short moment.

[From the Muv-Luv wiki]