 The Duchy of Luxembourg was formed when the counties of Luxembourg, Durbuy, Laroche and Vianden (a vassal county since 31 July 1264), the Marquisat of Arlon, and the districts of Thionville, Bitburg and Marville were combined.Luxembourg was an independent fief of the Holy Roman Empire until 1353, when the Luxembourg emperor Charles IV elevated it to the status of a duchy for his half-brother, Wenceslaus I, Duke of Luxembourg.Upon the extinction of the Luxembourg dynasty, the duchy passed to the House of Valois-Burgundy in 1443, and then to the Archduchy of Austria in 1482.