As soon as the Cathedral was completed, in 1520, it began to face problems; Luther had just nailed his theses at the nearby Wittenberg, and burnt there the Papal Bull. Although Protestantism spread rapidly in Germany, Magdeburg remained Catholic and gave rise to conflicts and iconoclasm in the Cathedral, breaking of images on the altars and mutilation of statues. The Cathedral also suffered when the town was besieged by the troops of Maurice of Saxony in 1550-51. (5) During the Thirty Years War, Magdeburg was besieged by the troops of General Tilly, who ravaged the town in 1631, and the Cathedral suffered from damage by fire. Again during the Napoleonic wars, from 1811 to 1813, the French troops used the nave of the church as a store for groceries, while church services were held in the choir. At the end of the war, the whole church was turned into a storeroom and sheepfold. In May 1814, the Prussians reconquered Magdeburg, and, on 29 May, a service of thanksgiving was held in the Cathedral. (6)