The Germans also mobilized their anti-tank guns, using light, obsolete or captured tracked vehicles. Examples include the Marder I, using captured French Lorraine 37L tractors, the Marder II, using the Panzer II light tank chassis, and the Marder III, which was based on the Panzer 38(t) Czech chassis. These led to better-protected Assault guns or Sturmgeschütz with fully enclosed casemates, built on medium tank chassis such as the Jagdpanzer IV and Jagdpanther. Some designs were based on existing chassis (such as the Brummbär), leftover chassis from cancelled programs (Elefant and Sturer Emil); others were converted from battle-damaged tanks (Sturmtiger). The single most-produced armored fighting vehicle design for Germany in WW II, the Sturmgeschütz III (StuG III) assault gun, in 1936–37 pioneered the later casemate-style fully enclosed armor that would be used on almost all late-war German self-propelled artillery and "Jagdpanzer"-format tank destroyers.