From the earlier part of the 15th century, Graz was the residence of the younger branch of the Habsburgs, which succeeded to the imperial throne in 1619 in the person of Emperor Ferdinand II, who moved the capital to Vienna. New fortifications were built on the Schlossberg at the end of the 16th century. Napoleon's army occupied Graz in 1797. In 1809, the city withstood another assault by the French army. During this attack, the commanding officer in the fortress was ordered to defend it with about 900 men against Napoleon's army of about 3,000. He successfully defended the Schlossberg against eight attacks, but they were forced to give up after the Grande Armée occupied Vienna and the Emperor ordered to surrender. Following the defeat of Austria by Napoleonic forces at the Battle of Wagram in 1809, the fortifications were demolished using explosives, as stipulated in the Peace of Schönbrunn of the same year. The belltower (Glockenturm) and the civic clock tower ("Uhrturm"), which is a leading tourist attraction and serves as a symbol for Graz, were spared after the citizens of Graz paid a ransom for their preservation.