He must up to this time have designed to make himself master of the great city, which had been the goal of so many previous invasions, and had always fallen whenever Rome attacked it.

But, having overcome all the obstacles in his path, and having it in his power at once to commence the siege, a sudden doubt appears to have assailed him as to the practicability of the undertaking.

It can scarcely be supposed that the city was really stronger now than it had been under the Parthians; much less can it be argued that Julian's army was insufficient for the investment of such a place.

It was probably the most powerful army with which the Romans had as yet invaded Southern Mesopotamia; and it was amply provided with all the appurtenances of war.

If Julian did not venture to attempt what Trajan and Avidius Cassius and Septimius Severus had achieved without difficulty, it must have been because the circumstances under which he would have had to make the attack were different from those under which they had ventured and succeeded.