the Reformed line had died out, too, with Friedrich Wilhelm's death, leading Charles VI, Holy Roman Emperor to transfer power in the territory to the Prince of Orange and the Prince of Nassau-Diez. Under their leadership, mining, the main source of wealth, blossomed, along with agriculture and silviculture. When Prince William of Orange refused to join the Confederation of the Rhine, founded by Napoleon, he found himself unseated by the French leader and the Siegerland passed to the Grand Duchy of Berg. After Napoleon's downfall in 1813, however, William I regained his former German inheritances, but in 1815 he ceded them to the Kingdom of Prussia for the Grand Duchy of Luxembourg. Siegen was assigned to the Siegen district, first in the Koblenz region, and as of 1817 in the Arnsberg region within the Prussian Province of Westphalia. Under Prussian rule, Siegen developed into the South Westphalian centre that it is today. On 1 March 1923, Siegen was set apart from the district bearing its name, and became a district-free town, while still keeping its function as seat of the district of which it was no longer part, and which was itself merged with Wittgenstein district under district reform in 1975. Siegen also lost its district-free status at this time, becoming part of the new Siegen-Wittgenstein district, the name that the district has borne since 1984. During World War II, Siegen was repeatedly bombed by the Allies owing to a crucial railroad that crossed through the town. On 1 April 1945, the US 8th Infantry Division began the Allied ground assault against Siegen and the dominating military-significant high ground north of the river. The battle against determined German forces at Siegen continued through 2 April 1945, until organized resistance was finally overwhelmed by the division on 3 April 1945. Religion The town of Siegen belonged in the beginning to the Archbishopric of Mainz, or more precisely to its deaconry of Arfeld. There was a White Nun convent in town that folded in the 15th century. Furthermore, there was a Franciscan Monastery that was dissolved in 1533 after the Nassau overlords had introduced the Reformation in 1530. After that, the town was first Lutheran, but in 1550, the Principality of Nassau converted to the Reformed Church. Subsequently, Siegen was a predominantly Protestant town, but not so strongly that the Counterreformation could not gain ground in 1623, with one fifth of the