 His son Leopold VI, sole ruler of the Austrian and Styrian lands from 1198, married the Byzantine princess Theodora Angelina and later married his daughter Margaret to Henry of Hohenstaufen, son of Emperor Frederick II, in 1225. Notable minnesingers like Reinmar von Hagenau and Walther von der Vogelweide were regular guests at the Vienna court and Middle High German poetry flourished.The poem "Nibelungenlied" probably arose in the Austrian lands.However, Leopold's son, Duke Frederick II the Warlike, entered into fierce conflicts soon after his accession in 1230, not only with the Austrian nobility, but also with King Wenceslaus I of Bohemia, King Andrew II of Hungary and even with Emperor Frederick II for the alleged entanglement in the rebellion of the duke's brother-in-law Henry of Hohenstaufen.