il the Christian control was so well established
as to make possible the Crusades. Later, as we shall see, a second
invasion of Mohammedans, the Turks, ably assisted by the descendants
of the Arabs who conquered Spain, once more threatened to control
the Mediterranean for the cause of Islam. But the Persian Gulf
and the Indian Ocean, which fell into the hands of the Arabs as
soon as they took to the water, remained in Arab hands down to
the times of the Portuguese. In those waters, because they were
cut off from the Mediterranean, the Saracen had no competitor.
As early as the eighth century Ceylon was an Arab trading base,
and when the Portuguese explorers arrived at the end of the 15th
century they found the Arabs still dominating the water routes
of India and Asia, holding as they had held for seven centuries
a monopoly of the commerce of the east.

Of the Mediterranean during the struggle between Christian and
Saracen a recent English writer makes the following suggestive comment:

"The function of the Mediterranean has thus undergone a change.
In early times it had been a barrier; later, under the Phoenicians,
it became a highway, and to the Greeks a defense. We find that the
Romans made it a basis for sea power and subdued all the lands
on its margin. With the weakening of Rome came a weakening of sea
power. The Barbary states and Spain became Saracen only because
the naval power of the eastern empire was not strong enough to hold
the whole sea, but neither was the Saracen able to gain supreme
control. Thus the conditions were the same as in the earlier days
of the conflict between Rome and Carthage: the Mediterranean became
a moat separating the rivals, though first one and then the other
had somewhat more control. The islands became alternately Saracen
and Christian. Crete and Sicily were held for centuries before
they were regained by a Christian power."[1]

[Footnote 1: GEOGRAPHY AND WORLD POWER, Fairgrieve, p. 125.]

The victory of 718 saved Constantinople from any further peril
from the Arabs, but it was again in grave peril, two centuries
later, when a sudden invasion of Russians in great force threatened
to accomplish at a stroke what the Saracens had failed to do in three
great expeditions. The King of Kiev, one of the race of Vikings
that had fought their way into southern Russia, collected a huge
number of ships, variously estimated from one to ten thousand, and
suddenly appeared in the Bosphorus.