THE GREAT CONQUESTS 31coast. The first tentative expedition set out with only 3,500 men, crossing
the frontier in late winter 639. This may be looked on as a reconnaissance-
in-force rather than a real invasion.
Egypt was the richest of the provinces of the Eastern Roman Empire,
just as it had been for the Western Empire. Egypt straddled the rich trade
routes to the Indian Ocean, and the incredibly rich alluvial soil of the Nile
delta made the land prosperous. For centuries the large Mediterranean
cities had counted on the Egyptian corn fleets to feed their populations.
This rich province should have been perfectly invincible against Arab
invasion, if only by reason of geography. The coastal road from Palestine
was blocked at Pelusium, just to the east of the easternmost arm of the
Nile Delta by a major fortress. This strongpoint could be easily resupplied
or reinforced by the Byzantine navy. The Nile itself was a major obstacle
on a scale that completely dwarfed the Tigris and Euphrates. The great
river of Egypt was navigable for hundreds of miles and unbridged. Thus
it could be a highway for Byzantine military and naval operations and a
barrier to those of the Arabs. A nearly impregnable fortress called, inter-
estingly enough, Babylon, held the apex of the channels to the south of
the Delta. Finally, Alexandria itself lay at the extreme western end of the
Delta and was a strongly fortified coastal city, again easily relieved by the
Byzantine fleet. To successfully attack these positions with fewer than
4,000 men was not possible. Had the Arabs attacked this stronghold when
the Empire was in order, Egypt could never have been taken. As it hap-
pened, Byzantine efforts in Egypt were completely futile, and in some
cases actually counterproductive.
When Amr ibn al Aasi’s little force arrived at Pelusium in the early
months of 640, they were reduced to the slow siege that was the only way
that they knew to capture a fortified city. How long the town might have
been held is uncertain, but in late January the garrison made a sortie. When
the Arabs counterattacked they managed to enter the town before the gates
could be barred, and the fortress fell. Even in Arab hands Pelusium re-
mained a problem; Amr had too few troops to garrison it, and if he left it
open, the Byzantines could easily reoccupy it with an amphibious force
and thus threaten his rear. To resolve this problem, the Arabs destroyed
the fort and then turned to the southwest to make for the huge fortress of
Babylon.
This Babylon—not the one in the Tigris Euphrates area—may have
been first named by Persian troops who conquered Egypt in the sixth
centuryB.C. Another story is that the fort was named by Babylonian pris-
oners who had been captured by an ancient pharaoh’s army. Whatever its
origins, the fortress was the most strategic place in Egypt. While Amr’s