The Persian shah, Khosrau II, had taken advantage of the internal turmoil of the East Roman Empire after the overthrow of Emperor Maurice by Phocas to attack the Roman provinces in the East. By 615, the Persians had driven the Romans out of northern Mesopotamia, Syria and Palestine. Determined to eradicate Roman rule in Asia, Khosrau turned his sight on Egypt, the East Roman Empire's granary.