The Panzerkampfwagen Mark IV was a German Medium tank designed in 1936 by Krupp and General Heinz Guderian. It was meant to be a support tank designed to take on Anti tank guns and enemy fortifications all the while complimenting the Panzer III. Early MK IV's were armed with the low velocity 75mm KwK 37 L/24 cannon. This cannon proved ineffective against allied armor during the battle of France and only penetrated their armor with great difficulty. In response the MK IV was up gunned to the long barreled 75mm KwK 40 L/43.
The MK IV first saw combat in the Invasion of Poland where it had little problem fighting the Polish FT-17s, 7TPs and TK-3s. However, during the battle of France the shortcomings of the Mk IVs low velocity 75mm cannon was exposed when it failed to penetrate French Char B1 Bis and British Matilda Is and IIs.
After the Battle of France the Mk IV was used in the North Africa theater still utilizing the low velocity 75mm. Once again it's shortcomings was it's downfall as it failed to effectively fight the allied Matilda's, M3 Lee's and M4 Shermans. Long barreled Mk IVs arrived later on but had arrived in too little numbers to make a difference. Around the same time the Mk IVs were used in the Invasion of the Soviet Union, this time however many of the Mk IVs had been equipped with the Long Barrel 75mm and made easy work of Soviet BT-7s and T-26 tanks.
After the arrival of T-34s and lend lease Sherman's on the Battlefield however the MK IV even with the long barrel had trouble fighting these tanks who had better guns and armor.
The MK IV was used through the entirety of the war and became known as the work horse of the German tank force.
In the Anime
Like it's real world counterpart, the MK IV saw combat in the invasion of Livonia and the Invasion of France. It went on to fight in Eylstadt during the opening offensive, It was used in the Battle of Coenenberg where it was effective against Eylstadt fixed positions. They were stopped short by Eylstadt artillery and after the arrival of Izetta the MK IVs were chalked up as mobility kills.