Michael I (Greek: Μιχαῆλ A) was Roman Emperor and Caliph of Islam from 859 to 864, the last of the Isaurian Dynasty. He succeeded his grandfather, Heraclius II, during a period of chaos and uncertainty that the empire was unprepared to deal with after the respite of the beginning of the century, and Michael soon found himself fighting for survival. In 860 he formed an alliance with Theodemar, the powerful king of Africa, giving himself the ability to call upon African assistance should the empire ever be in mortal danger.