 When the Uzbeks launched a large-scale invasion of Khorasan, the leader of the Ustalju Qizilbash faction in the province, Murshid Quli Khan, decided the time was right to overthrow the shah and replace him with Mohammad's son Abbas Mirza, who was Murshid's ward.Murshid and Abbas rode to Qazvin where the prince was proclaimed the new ruler of Iran in October 1587.Mohammad made no attempt to challenge the coup and accepted his dethronement.