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 were elected as Rex Romanorum and Emperor-to-be, none of whom were able to gain actual governing power upon the Emperor's death in 1250.
That same year, Ottokar II, son of King Wenceslaus I of Bohemia, 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 II gained the support of the local nobility and was proclaimed Austrian and Styrian duke by the estates one year later.

In 1253, Ottokar II became Bohemian king upon the death of his father; the concentration of power on the western Hungarian border was viewed with suspicion by King Béla IV, who campaigned against Austria and Styria but was finally defeated at the 1260 Battle of Kressenbrunn.
In 1268 Ottokar signed a contract of inheritance with Ulrich III, the last Carinthian duke of the House of Sponheim, and thus acquired Carinthia including the March of Carniola and the Windic March one year later.
At the height of his power he aimed at the Imperial crown, but the Princes-Electors (Kurfürsten), distrustful of his steep rise, elected the "poor Swabian count" Rudolph of Habsburg King of the Romans on 29 September 1273.
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 were elected as Rex Romanorum and Emperor-to-be, none of whom were able to gain actual governing power upon the Emperor's death in 1250. That same year, Ottokar II, son of King Wenceslaus I of Bohemia, 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 II gained the support of the local nobility and was proclaimed Austrian and Styrian duke by the estates one year later.
In 1253, Ottokar II became Bohemian king upon the death of his father; the concentration of power on the western Hungarian border was viewed with suspicion by King Béla IV, who campaigned against Austria and Styria but was finally defeated at the 1260 Battle of Kressenbrunn. In 1268 Ottokar signed a contract of inheritance with Ulrich III, the last Carinthian duke of the House of Sponheim, and thus acquired Carinthia including the March of Carniola and the Windic March one year later. At the height of his power he aimed at the Imperial crown, but the Princes-Electors (Kurfürsten), distrustful of his steep rise, elected the "poor Swabian count" Rudolph of Habsburg King of the Romans on 29 September 1273.
Battle on the Marchfeld