Ladislaus was crowned king in July 1162 by Mikó, Archbishop of Kalocsa, because Archbishop Lucas remained loyal to the expelled king and considered Ladislaus a usurper.
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".
The chronicle of Henry of Mügeln documented that the newly crowned King granted one-third of the Kingdom of Hungary to Stephen with the title of duke, while historian Florin Curta specified that Stephen's duchy included the southern regions of the kingdom.

Ladislaus II died on 14 January 1163.
Stephen was crowned king thirteen days later.
Mikó of Kalocsa once again performed the ceremony, because Lucas of Esztergom refused to crown him.
Lucas even excommunicated Stephen, declaring his rule unlawful.
According to the Gerhoh of Reichersberg, Stephen forbade the Hungarian prelates to send envoys to Pope Alexander III or to meet papal legates.

Stephen, who named himself Stephen III in his only preserved charter, "seemed grievous and was excessively oppressive to the principal personages" in Hungary, according to Kinnamos.
A group of Hungarian lords started conspiring against Stephen in favor of his expelled nephew.
At Stephen's request, Emperor Manuel sent an army to Hungary in March, however the news of the approaching imperial army strengthened Stephen's position, so he sent the Byzantines back.
But it was too late, and a rebellion broke out as soon as the Byzantine troops left Hungary.

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.
The decisive battle was fought at Székesfehérvár on 19 June 1163, with the elder Stephen routed by his nephew.
Stephen IV was captured during the battle, but his nephew soon released him upon Archbishop Lucas's advice.
Ladislaus was crowned king in July 1162 by Mikó, Archbishop of Kalocsa, because Archbishop Lucas remained loyal to the expelled king and considered Ladislaus a usurper. 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". The chronicle of Henry of Mügeln documented that the newly crowned King granted one-third of the Kingdom of Hungary to Stephen with the title of duke, while historian Florin Curta specified that Stephen's duchy included the southern regions of the kingdom.
Ladislaus II died on 14 January 1163. Stephen was crowned king thirteen days later. Mikó of Kalocsa once again performed the ceremony, because Lucas of Esztergom refused to crown him. Lucas even excommunicated Stephen, declaring his rule unlawful. According to the Gerhoh of Reichersberg, Stephen forbade the Hungarian prelates to send envoys to Pope Alexander III or to meet papal legates.
Stephen, who named himself Stephen III in his only preserved charter, "seemed grievous and was excessively oppressive to the principal personages" in Hungary, according to Kinnamos. A group of Hungarian lords started conspiring against Stephen in favor of his expelled nephew. At Stephen's request, Emperor Manuel sent an army to Hungary in March, however the news of the approaching imperial army strengthened Stephen's position, so he sent the Byzantines back. But it was too late, and a rebellion broke out as soon as the Byzantine troops left Hungary.
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. The decisive battle was fought at Székesfehérvár on 19 June 1163, with the elder Stephen routed by his nephew. Stephen IV was captured during the battle, but his nephew soon released him upon Archbishop Lucas's advice.
Stephen IV of Hungary