e petty kings of Osrhoene, Adiabene, and Hatra; but behind
them loomed the massive form of the Parthian State, which was attacked
through them, and could not be indifferent to their fortunes.

In the spring of A.D. 195, Severus, at the head of his troops, crossed
the Euphrates in person, and taking up his own quarters at Nisibis,
which the Mesopotamians had been unable to capture, proceeded to employ
his generals in the reduction of the rebels and the castigation of
their aiders and abettors. Though his men suffered considerably from the
scarcity and badness of the water, yet he seems to have found no great
difficulty in reducing Mesopotamia once more into subjection. Having
brought it completely under, and formally made Nisibis the capital, at
the same time raising it to the dignified position of a Roman colony,
he caused his troops to cross the Tigris into Adiabene, and, though
the inhabitants offered a stout resistance, succeeded in making himself
master of the country. The Parthian monarch seems to have made no effort
to prevent the occupation of this province. He stood probably on the
defensive, expecting to be attacked, in or near his capital. But Severus
could not afford to remain in these remote regions. He had still a rival
in the West in the person of Clodius Albinus, who might be expected to
descend upon Italy, if it were left exposed to his attacks much longer.
He therefore quitted the East early in A.D. 196, and returned to Rome
with all speed, leaving Parthia very insufficiently chastised, and his
new conquests very incompletely settled.

Scarcely was he gone when the war broke out with greater violence than
ever. Volagases took the offensive, recovered Adiabene, and crossing the
Tigris into Mesopotamia, swept the Romans from the open country.
Nisibis alone, which two years before had defied all the efforts of the
Mesopotamians, held out against him, and even this stronghold was
within a little of being taken. According to one writer, the triumphant
Parthians even crossed the Euphrates, and once more spread themselves
over the fertile plains of Syria. Severus was forced in A.D. 197 to make
a second Eastern expedition to recover his lost glory and justify the
titles which he had taken. On his first arrival in Syria, he contented
himself with expelling the Parthians from the province, nor was it till
late in the year, that, having first made ample preparation, he crossed
the Euphrates into Mesopotamia.

Th