od and pasturage in the countries left behind,
or the discovery of better living conditions in the neighboring
countries. But the impulse behind the two tremendous assaults of
Islam upon Europe seems to have been religious fanaticism of a
character and extent unmatched in history. The founder of the Faith,
Mohammed, taught from 622 to 632. He succeeded in imbuing his followers
with the passion of winning the world to the knowledge of Allah
and Mohammed his prophet. The unbeliever was to be offered the
alternatives of conversion or death, and the believer who fell in
the holy wars would be instantly transported to Paradise. Men who
actually believe that they will be sent to a blissful immortality
after death are the most terrible soldiers to face, for they would
as readily die as live. In fact Cromwell's "Ironsides" of a later
day owed their invincibility to very much the same spirit. At all
events, by the time of Mohammed's death all Arabia had been converted
to his faith and, fired with zeal, turned to conquer the world.
Hitherto the tribes of Arabia were scattered and disorganized,
and Arabia as a country meant nothing to the outside world. Now
under the leadership of the Prophet it had become a driving force
of tremendous power. Mohammedan armies swept over Syria into Persia.
In 637, only five years after Mohammed's death, Jerusalem surrendered,
and shortly afterwards Egypt was conquered. Early in the eighth
century the Arabs ruled from the Indus on the east, and the Caucasus
on the north, to the shores of the Atlantic on the west. Their
empire curved westward along the coast of northern Africa, through
Spain, like one of their own scimitars, threatening all Christendom.
Indeed, the Arab invasion stands unparalleled in history for its
rapidity and extent.

[Illustration: THE SARACEN EMPIRE AT ITS HEIGHT, ABOUT 715 A.D.]

The one great obstacle in the way was the Christian, or Roman,
empire with its center at Constantinople. Muaviah, the Emir of
Syria, was the first to perceive that nothing could be done against
the empire until the Arabs had wrested from it the command of the
sea. Accordingly he set about building a great naval armament.
In 649 this fleet made an attack on Cyprus but was defeated. The
following year, however, it took an important island, Aradus, off
the coast of Syria, once a stronghold of the Phoenicians, and sacked
it with savage barbarity. An expedition sent from Constantinople to
recover Alexa