During the Thirty Years' War, the Calvinist George William tried to remain neutral in the contest between the Catholic Emperor Ferdinand II, and his mostly Lutheran opponents. When the war shifted to northern Germany in 1625, this did not protect his lands from being looted by Imperial troops, and he was forced to take sides when Gustavus intervened in the Empire in 1630. However, this simply replaced one set of plunderers with another; Gustavus could not support so large an army, and his unpaid and unfed troops became increasingly mutinous and ill-disciplined.