Béla IV (1206 – 3 May 1270) was
King of Hungary and
Croatia between 1235 and 1270, and
Duke of Styria from 1254 to 1258. Being the oldest son of
King Andrew II, he was crowned upon the initiative of a group of influential noblemen in his father's lifetime in 1214. His father, who strongly opposed Béla's coronation, refused to give him a province to rule up until 1220. In this year, Béla was appointed
Duke of Slavonia, also with jurisdiction in
Croatia and
Dalmatia. Around the same time, Béla married
Maria, a daughter of
Theodore I Laskaris,
Emperor of Nicaea. From 1226, he governed
Transylvania with the title
Duke. He supported Christian missions among the pagan
Cumans who dwelled in the plains to the east of his province. Some Cuman chieftains acknowledged his suzerainty and he adopted the title of King of Cumania in 1233. King Andrew died on 21 September 1235 and Béla succeeded him. He attempted to restore royal authority, which had diminished under his father. For this purpose, he revised his predecessors' land grants and reclaimed former royal estates, causing discontent among the
noblemen and the
prelates.