During WWII, the German armed forces were by far the greatest user of half-track vehicles. Such vehicles were used in the Wehrmacht, Luftwaffe and Waffen-SS, where they served as personnel carriers, tractors, combat engineering vehicles, as well as self-propelled carriages for anti-aircraft guns. Sd.Kfz. 8 Schwerer Zugkraftwagen 12t - (heavy 12 ton half-track vehicle) -was a German half-track that saw widespread use in the war. Its main roles were as a prime mover for heavy towed guns such as the 21 cm Mörser 18, the 15 cm Kanone 18 and the 10.5 cm FlaK 38. Sd.Kfz. 9 Schwerer Zugkraftwagen 18t - (heavy 18 ton half-track vehicle) -was the Germans' heaviest half-track vehicle of any type built during the war years. Its main roles were as a prime mover for very heavy towed guns such as the 24 cm Kanone 3 and as a tank recovery vehicle.