great capitals of the East. In summer, the monarch of Persia
enjoyed at Ecbatana the cool breezes of the mountains of Media; but the
mildness of the climate engaged him to prefer Ctesiphon for his winter
residence.

From these successful inroads the Romans derived no real or lasting
benefit; nor did they attempt to preserve such distant conquests,
separated from the provinces of the empire by a large tract of
intermediate desert. The reduction of the kingdom of Osrhoene was an
acquisition of less splendor indeed, but of a far more solid advantage.
That little state occupied the northern and most fertile part of
Mesopotamia, between the Euphrates and the Tigris. Edessa, its capital,
was situated about twenty miles beyond the former of those rivers;
and the inhabitants, since the time of Alexander, were a mixed race
of Greeks, Arabs, Syrians, and Armenians. The feeble sovereigns of
Osrhoene, placed on the dangerous verge of two contending empires, were
attached from inclination to the Parthian cause; but the superior power
of Rome exacted from them a reluctant homage, which is still attested by
their medals. After the conclusion of the Parthian war under Marcus, it
was judged prudent to secure some substantia, pledges of their doubtful
fidelity. Forts were constructed in several parts of the country, and
a Roman garrison was fixed in the strong town of Nisibis. During the
troubles that followed the death of Commodus, the princes of Osrhoene
attempted to shake off the yoke; but the stern policy of Severus
confirmed their dependence, and the perfidy of Caracalla completed the
easy conquest. Abgarus, the last king of Edessa, was sent in chains to
Rome, his dominions reduced into a province, and his capital dignified
with the rank of colony; and thus the Romans, about ten years before
the fall of the Parthian monarchy, obtained a firm and permanent
establishment beyond the Euphrates.

Prudence as well as glory might have justified a war on the side of
Artaxerxes, had his views been confined to the defence or acquisition
of a useful frontier. but the ambitious Persian openly avowed a far more
extensive design of conquest; and he thought himself able to support his
lofty pretensions by the arms of reason as well as by those of power.
Cyrus, he alleged, had first subdued, and his successors had for a long
time possessed, the whole extent of Asia, as far as the Propontis and
the AEgean Sea; the provinces of Caria and Ionia, und