At the unwinding of the Holy Roman Empire in 1806 the Free Imperial City of Bremen (as of 1646, after earlier privileges of autonomy of 1186) was not mediatised but became a sovereign state officially titled Free Hanseatic City of Bremen. Its currency was the Bremen thaler (until 1873). In 1811 the First French Empire annexed the city-state. Upon the first, albeit only preliminary, defeat of Napoléon Bonaparte, Bremen resumed its pre-1811 status as city-state in 1813. The Vienna Congress of 1815 confirmed Bremen's—as well as Frankfurt's, Hamburg's, and Lübeck's—independence after pressuring by Bremen's emissary, and later burgomaster, Johann Smidt. Bremen became one of 39 sovereign states of the German Confederation.