The deposition of Emperor Frederick II of…

The deposition of Emperor Frederick II of Hohenstaufen by Pope Innocent IV in 1245 created a grave crisis for the Holy Roman Empire, as in the following decades several nobles have been elected as Rex Romanorum and Emperor-to-be, none of whom had been able to gain actual governing power upon the Emperor's death in 1250.

That same year, Ottokar, son of king Wenceslaus I of Bohemia, had moved into the princeless Duchies of Austria and Styria.

The last Babenberg duke Frederick II of Austria had been killed at the 1246 Battle of the Leitha River, in a border conflict he had picked with King Béla IV of Hungary.

Ottokar, having gained the support of the local nobility, had been proclaimed Austrian and Styrian duke by the estates one year later.

He becomes Bohemian king Ottokar II upon the death of his father in 1253; the concentration of power on the western Hungarian border had been viewed with suspicion by King Béla IV, who campaigned against Austria and Styria but was finally defeated at the 1260 Battle of Kressenbrunn.

King Ottokar II of Bohemia inherits Carinthia and part of Carniola in 1269, making him the most powerful prince within the Holy Roman Empire as well one of the most powerful men in Europe.