The Euphrates was therefore crossed by his adversary in the spring of A.D.

232; the Roman province of Mesopotamia was easily recovered; and arrangements were made by which it was hoped to deal the new monarchy a heavy blow, if not actually to crush and conquer it.
Alexander divided his troops into three bodies.

One division was to act towards the north, to take advantage of the friendly disposition of Chosroes, king of Armenia, and, traversing his strong mountain territory, to direct its attack upon Media, into which Armenia gave a ready entrance.

Another was to take a southern line, and to threaten Persia Proper from the marshy tract about the junction of the Euphrates with the Tigris, a portion of the Babylonian territory.

The third and main division, which was to be commanded by the emperor in person, was to act on a line intermediate between the other two, which would conduct it to the very heart of the enemy's territory, and at the same time allow of its giving effective support to either of the two other divisions if they should need it.
The plan of operations appears to have been judiciously constructed, and should perhaps be ascribed rather to the friends whom the youthful emperor consulted than to his own unassisted wisdom.