When Emperor Frederick II deposed his eldest son, Conrad's rebellious half-brother King Henry (VII), Conrad succeeded him as Duke of Swabia in 1235. However, the emperor was not able to have him elected King of the Romans until the 1237 Imperial Diet in Vienna. The electors were "The Archbishops of Mentz of Treves [Trier, and of Cologne, the Bishops of "Bamberg", of "Ratisbon" of "Frisingen" [Freising, and of "Padua", the Count Palatine of the Rhine, "the Duke of Bavaria", the King of Bohemia, the "Landgrave of Thuringia", and the "Duke of Carinthia"". This title, though not acknowledged by Pope Gregory IX, presumed his future as a Holy Roman Emperor. Prince-Archbishop Siegfried III of Mainz, in his capacity as German archchancellor, acted as regent for the minor until 1242, when Frederick chose Landgrave Henry Raspe of Thuringia, and King Wenceslaus I of Bohemia to assume this function. Conrad intervened directly in German politics from around 1240. He led the short-lived anti-Mongol crusade of 1241.