Although some former rulers of Bohemia had enjoyed a non-hereditary royal title during the 11th and 12th centuries (Vratislaus II, Vladislaus II), the kingdom was formally established in 1198 by Přemysl Ottokar I, who had his status acknowledged by Philip of Swabia, elected King of the Romans, in return for his support against the rival Emperor Otto IV. In 1204 Ottokar's royal status was accepted by Otto IV as well as by Pope Innocent III. It was officially recognized in 1212 by the Golden Bull of Sicily issued by Emperor Frederick II, elevating the Duchy of Bohemia to Kingdom status and proclaiming its independence which was also later bolstered by future king of Bohemia and emperor Charles IV. with his golden bull in 1356.