Béla III of Hungary

Béla was the second son of Géza II, granted a duchy that included Croatia around 1161. A peace treaty shipped him to Constantinople in 1163, where Manuel I Komnenos renamed him Alexios, gave him the new title of despotes, and betrothed him to the imperial daughter. He was designated heir in 1165 and rode in three campaigns against his own brother's Hungary. The birth of Manuel's son in 1169 ended the engagement and demoted him to kaisar. When Stephen III died in March 1172, Béla returned and took the Hungarian throne, pledging never to war against Byzantium. He fought his younger brother Géza and held him captive for over a decade. After Manuel's death he retook Croatia, Dalmatia and Sirmium, then briefly occupied Halych before losing it. He promoted written governance, built the first Gothic palace in Central Europe at Esztergom, and was listed as the wealthiest monarch of his age.