The Peace of Westphalia finally settled the Thirty Years' War in 1648. Three years later, the Holy Roman Empire found itself on the brink of war when Wolfgang Wilhelm claimed that the normative year imposed by the treaty took precedence over the Treaty of Xanten in regard to church properties. Since more parishes were in Catholic hands in 1624 than a decade before, Wolfgang Wilhelm hoped to stabilize his control over Jülich and Berg. The Aulic Council was still reviewing the evidence when Frederick William declared himself a protector of the Protestant population living in the two duchies. In June 1651, 3,800 Brandenburg troops invaded Berg, killing two civilians, bombarding Wolfgang Wilhelm's palace and seizing a herd of cows belonging to his wife. After rallying at Kaßlerfeld, the Brandenburgers created an encampment at Angermund and unsuccessfully beleaguered Düsseldorf. The Neuburg envoy in Vienna described the incident as a "Cow War", comparing Brandenburg's ruler to a cattle rustler. By July, Brandenburg had reinforced its expedition by 2,700 troops, mobilizing 16,000 more across its various territories. Wolfgang Wilhelm employed the help of Charles IV, Duke of Lorraine, who launched a counter invasion of Mark with the intention of obtaining provisions for his army. The estates of all five duchies refused to provide money to either side, while Duisburg's city council requested Dutch protection. The Dutch condemned the actions of their former ally, while Sweden persuaded both sides to disengage through their envoy Melchior von Hatzfeldt. By the end of the year, Neuburg and Brandenburg had disbanded their troops. The Aulic Council distributed the church property on the basis of the current year, ending the conflict. Further negotiations in 1666 and 1672 confirmed the 1651 arrangements, putting an end to the dispute.. What year did Wolfgang Wilhelm claim that the normative year imposed by the treaty took precedence over the Treaty of Xanten in regards to church properties?