established along the southern frontier of Hungary in the 1250s. Béla's relationship with his oldest son and heir, Stephen, became tense in the early 1260s, because the elderly king favored his daughter Anna and his youngest child, Béla, Duke of Slavonia. He was forced to cede the territories of the Kingdom of Hungary east of the river Danube to Stephen, which caused a civil war lasting until 1266. Nevertheless, Béla's family was famed for his piety: he died as a Franciscan tertiary, and the veneration of his three saintly daughters—Kunigunda, Yolanda, and Margaret—was confirmed by the Holy See. Childhood (1206–20) Béla was the oldest son of King Andrew II of Hungary by his first wife, Gertrude of Merania. He was born in the second half of 1206. Upon King Andrew's initiative, Pope Innocent III had already appealed to the Hungarian prelates and barons on 7 June to swear an oath of loyalty to the King's future son. Queen Gertrude showed blatant favoritism towards her German relatives and courtiers, causing widespread discontent among the native lords. Taking advantage of her husband's campaign in the distant Principality of Halych, a group of aggrieved noblemen seized and murdered her in the forests of the Pilis Hills on 28 September 1213. King Andrew only punished one of the conspirators, a certain Count Peter, after his return from Halych. Although Béla was a child when his mother was assassinated, he never forgot her and declared his deep respect for her in many of his royal charters. Andrew II betrothed Béla to an unnamed daughter of Tzar Boril of Bulgaria in 1213 or 1214, but their engagement was broken. In 1214, the King requested the Pope to excommunicate some unnamed lords who were planning to crown Béla king. Even so, the eight-year-old Béla was crowned in the same year, but his father did not grant him a province to rule. Furthermore, when leaving for a Crusade to the Holy Land in August 1217, King Andrew appointed John, Archbishop of Esztergom, to represent him during his absence. During this period, Béla stayed with his maternal uncle Berthold of Merania in Steyr in the Holy Roman Empire. Andrew II returned from the Holy Land in late 1218. He had arranged the engagement of Béla and Maria, a daughter of Theodore I Laskaris, Emperor of Nicaea. She accompanied King Andrew to Hungary and Béla married her in 1220. Rex