The Polish military campaign revealed the weak armor protection of the early German Panzer IV tanks, which could be easily damaged with light anti-tank artillery. The German engineers eliminated this flaw by reinforcing the front and side armor with additional armored plates, also the commander's cupola was changed. The increased tank weight was compensated by wider tracks. Many smaller changes were applied to the design, such as a new drivers vision device and a different turret roof. The Pz IV Ausf. E tanks fought in the Balkans, North Africa and the Eastern Front in Russia.