The Sd.Kfz.251 medium half-tracked armoured personnel carrier was developed by Hanomag in 1938 on the basis of the Sd.Kfz.11 artillery tractor. The vehicle was fully armoured, with an open combat compartment on top and double doors in the rear. The main armament was MG 34 machine guns. Production of the armoured personnel carrier began before the outbreak of World War II, with the first model being the Ausf A version, and production of later modifications continued until the spring of 1945. During the Second World War, the Sd.Kfz.251 was the main armoured personnel carrier of Germany, and it also became the base vehicle for combat vehicles for various purposes. The Sd.Kfz.251/18 variant (mittlerer Beobachtungspanzerwagen) was an armoured personnel carrier for observation and communications, distinguished by a map table mounted on the roof of the control room. Some of these combat vehicles remained armed with an MG 34 machine gun with a shield. Some of these armoured personnel carriers were also equipped with S.F.14Z rangefinders for observation, targeting and distance determination.