The Panzer IV was the main workhorse medium tank for the German Army during WW2. Starting the war with an infantry support gun it ended it completely transformed into a tank hunting machine with a long 75mm gun. Although eclipsed by the Panther and the Tiger it was nevertheless more than a match for the Soviet T-34 hordes.
As an infantry support tank the Panzer IV D proved to be fitted for the job. Sporting decent armor (by 1940 standards) and a short 75mm gun it gave good results when used to blast holes in the enemy defense. The reliability of its chassis was also superb, as it allowed new variants (with better anti-tank capabilities) to be developed.
Starting the war as an infantry support tank, the Panzer IV quickly became the mainstay of the German armed forces as a reliable medium tank which suffered countless modifications which kept it a dangerous enemy until the end of the war!