Shortly afterwards he moved to the Byzantine Empire, where he married a niece of Emperor Manuel I Komnenos, Maria Komnene, and converted to the Eastern Orthodox Church.

Although the Hungarian lords were willing to leave their young monarch, they sharply opposed Stephen and elected his brother, Ladislaus II, king.

Lucas, Archbishop of Esztergom, who remained a staunch supporter of the expelled young Stephen III, denied to crown him and excommunicated him.

In the decisive battle, which was fought at Székesfehérvár on 19 June 1163, the younger Stephen routed his uncle, forcing him once again to flee Hungary.

[1][2] The earliest recorded event of Stephen's life occurred during the reign of his oldest brother, Géza II, who succeeded their father on 13 February 1141.

However, scholars Ferenc Makk and Gyula Kristó claim it was later, in about 1152, at the same time Géza II officially appointed his son, Stephen, as his heir.

[7] In fear of being seized and executed by his brother, Stephen sought refuge in the Holy Roman Empire in summer 1157.

But the king, suspicious of the great attention paid to his brother, and fearing worse things from him than was needful, now openly accused not the man himself so much as his friends and those of his household, and turned all that they said or did against him.

After many accusations had been aired and many persons induced to bear false witness, the king was said to be planning to have his brother killed.

[8] Frederick I initially contemplated that "the dispute must be terminated either by a division of the realm or by the condemnation of one or the other", but finally "decided to defer to a more suitable time the settlement of this quarrel",[11] because he was planning to invade Italy.

[25] Stephen received "the rank of urum" ("Mylord") from his brother, because "among the Hungarians, this name means he who will succeed to the royal authority".

[31] According to the Gerhoh of Reichersberg, Stephen forbade the Hungarian prelates to send envoys to Pope Alexander III or to meet papal legates.

[34] With Emperor Frederick I's approval, the expelled young Stephen mustered an army of German mercenaries and discontented Hungarian lords, and launched a campaign against his uncle.

[40][37] According to that treaty, the young King agreed to allow the Byzantines to take possession of Syrmium and other parts of his kingdom in exchange for Manuel's renouncing any further support for his uncle.

[42] Stephen, who was staying in Anchialus on the Black Sea (now Pomorie in Bulgaria), stormed into Syrmium in summer of 1164, winning over many inhabitants while marching through the region.

In bleeding [Stephen's] vein, he smeared with poison the bandage which covered the wound; from there it spread and diffused throughout the body and penetrated into the most vital parts and removed the man from life, thereby clearly confirming the uncertain and cowardly devices of men.