The Panzerkampfwagen IV (Pz.Kpfw. IV), commonly known as the Panzer IV, was a German medium tank developed in the late 1930s and used extensively during the Second World War. Its ordnance inventory designation was Sd.Kfz. 161. The Panzer IV was the most numerous German tank and the second-most numerous German fully tracked armored fighting vehicle of the Second World War; 8,553 Panzer IVs of all versions were built during World War II, only exceeded by the StuG III assault gun with 10,086 vehicles. Its chassis was also used as the base for many other fighting vehicles, including the Sturmgeschütz IV assault gun, the Jagdpanzer IV tank destroyer, the Wirbelwind self-propelled anti-aircraft gun, and the Brummbär self-propelled gun.
The Ausf. H - began production in June 1943 and received the designation Sd. Kfz. 161/2. The integrity of the glacis armor was improved by manufacturing it as a single 80-millimetre plate. A reinforced final drive with higher gear ratios was introduced. The turret roof was reinforced from 10-millimetre to 16-millimetre and 25-millimetre segments. During the Ausf. H's production run, its rubber-tired return rollers were replaced with cast steel, a lighter cast front sprocket and rear idler wheel gradually replaced the previous components, the hull was fitted with triangular supports for the easily damaged side skirts, the Nebelwurfgeraet was discontinued, and a mount in the turret roof, designed for the Nahverteidigungswaffe, was plugged by a circular armored plate due to initial production shortages of this weapon.
The Ausf. J - was considered a retrograde from the Ausf. H. Born of necessity, to replace heavy losses, it was greatly simplified to speed production. The electric generator that powered the tank's turret traverse was removed, so the turret had to be rotated manually. The turret traversing mechanism was modified and fitted with a second gear which made hand-operation easier when the vehicle was on sloping terrain.