In September 640, the Arab army of Amr ibn al-As appeared before the walls of Babylon. The Byzantine (as the Romans were now called) garrison opened the gates and allowed refugees from the surrounding communities to enter the stronghold. Finally, in April 641, Babylon surrendered. The victorious general decided to establish an entirely new city to protect the land lifeline between the river and Arabia. These instructions meant that the new town of Fustat would be on the eastern bank of the Nile to ensure that the inhabitants and the army would always be able to walk to Arabia (or sail once the old Roman canal reopened in 643). For the next twelve centuries, urban growth was confined to the eastern bank of the Nile, a trend that sealed the fate of nearby Memphis and created the modern Cairo as we know it.