the defensive anti-tank role. The StuG III assault gun was Germany's most-produced fully tracked armoured fighting vehicle during World War II, and second-most produced German armoured combat vehicle of any type after the Sd.Kfz. 251 half-track. Although the early German Panzerjäger carried more effective weapons than the tanks on which they were based, they were generally lacking in protection for the crew, having thinly armoured open-topped superstructures. The "open-topped" design format of the Panzerjäger vehicles was succeeded by the Jagdpanzer ("hunting tanks"), which mounted the gun in true casemate-style superstructures, completely enclosing the crew compartment in armor that was usually integral to the hull. The first of these Jagdpanzers was the 70-ton Ferdinand (later renamed Elefant), based on the chassis, hulls, and drive systems of ninety-one Porsche VK4501 (P) heavy tanks, mounting a long-barreled 88 mm cannon in an added casemate, more like the earlier Panzerjägers had with their added-on armour shielding for the gun crew, but in the Ferdinand completely enclosing the gun and firing crew in the added casemate, as the later purpose-built Jagdpanzers would. However, the Ferdinand was mechanically unreliable and difficult to maneuver, and once all ninety-one unturreted "Porsche Tiger" hulls/drive systems were converted, no more were built. The German Army had more success with the Jagdpanther. Introduced in mid-1944, the Jagdpanther, of which some 415 examples were produced, was considered the best of the casemate-design Jagdpanzer designs. It featured the same powerful PaK 43 88 mm cannon used on the unwieldy Elefant, now fitted to the chassis of the medium Panther tank, providing greatly improved armour-penetrating capability in a medium-weight vehicle. Facing an increasingly defensive war, the German Army turned to larger and more powerfully armed Jagdpanzer designs, and in July 1944 the first Jagdtiger rolled off the production line; it was the heaviest German armoured fighting vehicle to go into active service. The Jagdtiger was based on the Tiger II heavy tank featured a very large 128 mm PaK 44 cannon and heavy armour protection. Only 88 Jagdtiger vehicles were produced, barely matching the total number of the earlier Ferdinand / Elefant vehicles. They were first deployed to combat units in September 1944. The decision of German armoured vehicle designers to use a casemate-style superstructure for all tank destroyers had the advantage of a reduced silhouette, allowing the crew to more frequently fire from defilade ambush positions. Such designs were also easier and faster