In June 1943 the production of Pz.Kpfw. IV Ausf. H began in order to
increase the armor piercing capabilities of its main armament. Although
the new model received the modified 75-mm KwK43 L/48 tank gun, the Ausf.
H was still sharing many components with the previous version. This
Panzer IV version first saw combat in the summer of 1943 during the
German retreat on the Eastern front. The tank proved to be quite
complicated and labor-consuming in production which led to simplifying
its design. As a result, the less complex Ausf. J model was introduced
into production in June 1944.