To legitimate Legality his succession , Ottokar in 1252 married Forming_relationships the Duchess Margaret of Austria , the sister of the last Babenberg duke and about 26 years his senior .

When Ottokar followed Removing his father as King of Bohemia in 1253 , Béla , distrustful of his rising Cause_change_of_position_on_a_scale power , claimed Statement the Styrian duchy .

However Ottokar called back his forces Causation and managed Resolve_problem to repulse Attack Stephen who was seriously injured Bodily_harm .

The Bohemian forces were led by King Ottokar II Přemysl , while the Hungarians were led by King Béla IV .

In 1251 Ottokar 's father King Wenceslaus I of Bohemia had not only granted Giving him the title of a Margrave of Moravia but also installed Placing him as duke of Austria and Styria , territories that were princeless after the ruling Babenberg dynasty Change_of_leadership had become Becoming extinct in 1246 .

However , in 1260 the conflict Hostile_encounter rekindled Recovering , after the Styrian nobility had revolted Change_of_leadership against the Árpáds and Ottokar campaigned Military_operation the duchy .

Béla allied Collaboration with Daniel of Galicia and Bolesław V the Chaste of Poland and marched Self_motion against Ottokar .

Historians estimate Statement that up to half of Hungary 's then population of 2,000,000 were victims Death of the Mongol invasion Ottokar 's troops consisted of Bohemian-Moravian , German , Polish , Carinthian , Carniolan and Styrian forces , while Bela 's huge army gathered Come_together Hungarian , Slovak , Cuman , Russian , Polish , Bulgarian , Wallachian , Ukrainian ( Galician ) , Slavonian , Croatian , Bosnian , Serbian , Pecheneg and Szekler contingents .

As none of the belligerents dared Risk to cross Motion_directional the river , Ottokar proposed Statement an agreement Sign_agreement , that his troops Motion would withdraw Escaping to give Giving the Hungarians the opportunity to go Self_motion reach Arriving the other bank .

After Ottokar 's victory Earnings_and_losses King Béla renounced Surrendering the Duchy of Styria and in 1261 even arranged Arranging the marriage Forming_relationships of his granddaughter Kunigunda of Slavonia with the Bohemian king .