32 ISLAM AT WAR
troops sat waiting at Pelusium, Theodore, the governor of the province,
had moved troopships down the Nile and completed the garrison. When
the Arabs arrived outside the fortress they were in a difficult spot. To cross
the Nile they would have to find boats and not only risk attack by the
Byzantine ships, but also risk being cut off from reinforcements, or escape
if matters turned sour. Laying siege to a city on a great and navigable
river was out of the question, and a storming attack would have been
impossible against the sixty-foot-high walls of the great citadel. Amr,
perhaps judging his opponent correctly, simply marched fifty miles south,
forced boats from the local inhabitants, and crossed the river. The Byz-
antines stood by passively and did not interfere.
Once across the Nile, Amr skirmished and raided up and down the west
bank of the River but had too few men to accomplish much more. His
problem had already been remedied, for the caliph had sent reinforce-
ments, a body of 12,000 men from Medina to operate under Amr’s com-
mand. These arrived in June, and again the Byzantines watched both parts
of the Arab army, and struck neither, thus giving up an opportunity to
defeat an enemy in detail. In July, though, with the Arabs united and on
the east bank, Governor Theodore finally brought his army into action.
The Byzantine force of unknown size marched out of Babylon to attack
the Arab camp at Heliopolis. Possibly Theodore was desperate, and pos-
sibly he thought that the Arabs should be attacked before they became
even stronger. Amr, for his part, deployed his main force to block the
Byzantine attack but concealed two small flanking parties in front of his
main line. When the imperials attacked, these struck in succession, and
shattered the Byzantine army. Remarkably, this tactic was well known in
Byzantine military manuals. It says something for the growing sophisti-
cation of the Muslim armies that they could plan such a clever trap. It
also says something about their opponents, who were tricked by one of
their own devices!
The Battle of Heliopolis, fought in July 640, was the only major field
action in the conquest of Egypt. Babylon was such a strong position that
it held out until April of the next year. Even then, the garrison accepted
generous terms. The surrender was not a military necessity but a political
one, caused in the end by the throne’s support in the suppression of the
heresies that the Alexandrians so loved. Alexandria itself, the greatest city
in the Mediterranean basin, surrendered meekly in September 642. Again,
politics, not swords caused the fall of the city.
It would be difficult to overstate the feebleness of the imperial defense
of the Empire’s richest province. The Byzantines had many problems and
dealt well with none of them. Heraclius had died, and his succession was