How did the Holy Roman Emperor Ferdinand II (a Hapsburg) pay his army?

He would allow them to steal and to plunder across the territories of the Holy Roman, where he ruled.

Explanation:

Ferdinand II was the ruler of the Holy Roman Empire during the Thirty Years War. He was engaged in one of the greatest wars that spread across his country and wasn't able to always collect as many troops as needed. That is why quite often mercenaries were a part of his army. The ruthless methods that were used to pay his army were one of the problems that he had with his subjects.

answer; taking up arms to defend the nation;