In June 1943 the production of Pz.Kpfw. IV Ausf. H began in order to increase the armour 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 labour-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.