The german Panzer IV was initially planned as support tank for the lighter tank Panzer III as it had a gun with a bigger calibre.
But it became the backbone of the tank troops as it was the only german tank which was used during world war II completely.
The first version A tanks of Panzer IV were produced in 1936/37 while the last version J was produced until 1945.
Beside Panzer IV some derivates were produced as well:
Sturmgeschuetz IV as assault gun and Jagdpanzer IV as tank hunter as well as Sturmpanzer IV as infantry support tank against emplacements.
Geschuetzwagen (Gw) III/IV as tank howitzer “Hummel” and tank hunter Hornisse / Nashorn.
Anti-aircraft gun (Flak = Flugawehrkanone) carrier “Moebelwagen” with 4 x 2 cm or 1 x 3,7 cm anti-aircraft gun covered with tank plates which had to be lowered during combat , “Wirbelwind” with 4 x 2 cm and “Ostwind” with 1 x 3,7 cm anti-aircraft gun – both in a turret, opened at the top and Flakpanzer IV “Kugelblitz” with 2 x 3cm anti-aircraft guns in a turret.
Additionally a recovery tank IV and an ammunition transporter tank IV were produced. For example for the Geraet 040 heavy mortar “Karl”.