on the other. His son Cambyses even succeeded in adding Egypt for
a time to the Persian Empire. The oyster-shell of history had
accordingly expanded to include almost the whole of Western Asia.

The next two centuries are taken up in universal history by the
magnificent struggle of the Greeks against the Persian Empire--the
most decisive conflict in all history, for it determined whether
Europe or Asia should conquer the world. Hitherto the course of
conquest had been from east to west, and if Xerxes' invasion had
been successful, there is little doubt that the westward tendency
would have continued. But the larger the tract of country which an
empire covers--especially when different tribes and nations are
included in it--the weaker and less organised it becomes. Within
little more than a century of the death of Cyrus the Great the
Greeks discovered the vulnerable point in the Persian Empire, owing
to an expedition of ten thousand Greek mercenaries under Xenophon,
who had been engaged by Cyrus the younger in an attempt to capture
the Persian Empire from his brother. Cyrus was slain, 401 B.C., but
the ten thousand, under the leadership of Xenophon, were enabled,
to hold their own against all the attempts of the Persians to destroy
them, and found their way back to Greece.

Meanwhile the usual process had been going on in Greece by which a
country becomes consolidated. From time to time one of the tribes
into which that mountainous country was divided obtained supremacy
over the rest: at first the Athenians, owing to the prominent part
they had taken in repelling the Persians; then the Spartans, and
finally the Thebans. But on the northern frontiers a race of hardy
mountaineers, the Macedonians, had consolidated their power, and,
under Philip of Macedon, became masters of all Greece. Philip had