Born in present-day Cluj-Napoca in Transylvania (then Kolozsvár), he was the son of a successful military leader of Romanian and Hungarian descent who had risen through the ranks of the nobility to become regent of Hungary. He was elected King when he was barely 15, and during his reign Hungary reached its greatest territorial extent of the epoch (present-day southeastern Germany to the west, Dalmatia to the south, Eastern Carpathians to the east, and southwestern Poland to the north).