It was the first act of his reign to march the forces of the empire to the extreme east, and to commence in earnest the war which had so long been threatened.

Led by the Emperor in person, the legions once more crossed the Euphrates.
Mesopotamia was rapidly overrun, since the Persians (we are told) were at variance among themselves, and a civil war was raging.

The bulk of their forces, moreover, were engaged on the opposite side of the empire in a struggle with the Indians, probably those of Afghanistan.

Under these circumstances, no effectual resistance was possible; and, if we may believe the Roman writers, not only was the Roman province of Mesopotamia recovered, but the entire tract between the rivers as far south as the latitude of Bagdad was ravaged, and even the two great cities of Seleucia and Ctesiphon were taken without the slightest difficulty.

Persia Proper seemed to lie open to the invader, and Carus was preparing to penetrate still further to the east, when again an opportune death checked the progress of the Roman arms, and perhaps saved the Persian monarchy from destruction.