When the king of a great unified Iberia, Bakur III, died in 580, the Sassanid government of Persia under Hormizd IV (578-590) seized on the opportunity to abolish the Iberian monarchy. Iberia became a Persian province ruled by a "marzpan" (governor). The Iberian nobles acquiesced to this change without resistance, while the heirs of the royal house withdrew to their highland fortresses – the main Chosroid line in Kakheti, and the younger Guaramid branch in Klarjeti and Javakheti. However, the direct Persian control brought about heavy taxation and an energetic promotion of Zoroastrianism in a largely Christian country. Therefore, when the Eastern Roman emperor Maurice embarked upon a military campaign against Persia in 582, the Iberian nobles requested that he helped restore the monarchy. Maurice did respond, and, in 588, sent his protégé, Guaram I of the Guaramids, as a new ruler to Iberia. However, Guaram was not crowned as king, but recognized as a presiding prince and bestowed with the Eastern Roman title of "curopalates". The Byzantine-Sassanid treaty of 591 confirmed this new rearrangement, but left Iberia divided into Roman- and Sassanid-dominated parts at the town of Tbilisi.