338) Sapor took the field in greater force than before, and addressed himself to an important enterprise.

He aimed, it is evident, from the first, at the recovery of Mesopotamia, and at thrusting back the Romans from the Tigris to the Euphrates.

He found it easy to overrun the open country, to ravage the crops, drive off the cattle, and burn the villages and homesteads.

But the region could not be regarded as conquered, it could not be permanently held, unless the strongly fortified posts which commanded it, and which were in the hands of Rome, could be captured.
Of all these the most important was Nisibis.

This ancient town, known to the Assyrians as Nazibina, was, at any rate from the time of Lucullus, the most important city of Mesopotamia.