Before the First World War, the problem of aviation worried already the German high command. One thus developed a series of anti-aircraft gun-cars (BAK - Balloon-Abwehr-Kanone). The first model was Ehrardt gun-car in 1906-1907. This vehicle was built from a truck with an elaborate shielding and an anti-aircraft gun Rheinmetall of 50 mm assembled in a fixed turret in the center of the vehicle. It was intended to fight as well against the planes and airships and as against terrestrial objectives. However the models which started production were stripped of shielding.