As in the former cases, so in this, sectarian treason assisted them.

The Saracen army was hailed as the deliverer of the Jacobite Church; the Monophysite Christians of Egypt, that is, they who, in the language of the Athanasian Creed, confounded the substance of the Son, proclaimed, through their leader, Mokaukas, that they desired no communion with the Greeks, either in this world or the next, that they abjured forever the Byzantine tyrant and his synod of Chalcedon.

They hastened to pay tribute to the khalif, to repair the roads and bridges, and to supply provisions and intelligence to the invading army.
FALL OF ALEXANDRIA.

Memphis, one of the old Pharaonic capitals, soon fell, and Alexandria was invested.

The open sea behind gave opportunity to Heraclius to reenforce the garrison continually.