 Complete the following phrase:  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 