After the Protestant Reformation, the Catholic Habsburgs had to accept the 1555 Peace of Augsburg and failed to strengthen their Imperial authority in the disastrous Thirty Years' War. Upon the 1648 Peace of Westphalia, Austria had to deal with the rising Brandenburg-Prussian power in the north, that replaced the Electorate of Saxony as the leading Protestant estate. The efforts made by the "Great Elector" and the "Soldier-king" Frederick William I had created a progressive state with a highly effective Prussian Army that, sooner or later, had to collide with the Habsburg claims to power.[3]