Crassus felt himself compelled to support his garrisons, and therefore to make Mesopotamia, and not Armenia, the basis of his operations, He crossed the Euphrates a second time at the same point as before, with an army composed of 35,000 heavy infantry, 4,000 light infantry, and 4,000 horse.

There was still open to him a certain choice of routes.

The one preferred by his chief officers was the line of the Euphrates, known as that which the Ten Thousand had pursued in an expedition that would have been successful but for the death of its commander.

Along this line water would be plentiful; forage and other supplies might be counted on to a certain extent; and the advancing army, resting on the river, could not be surrounded.

Another, but one that does not appear to have been suggested till too late, was that which Alexander had taken against Darius; the line along the foot of the Mons Masius, by Edessa, and Nisibis, to Nineveh.