Yet Galerius took the offensive.

Fighting under the eye of a somewhat stern master, he was scarcely free to choose his plan of campaign.

Diocletian expected him to drive the Persians from Mesopotamia, and he was therefore bound to make the attempt.

He accordingly sought out his adversary in this region, and engaged him in three great battles.

The first and second appear to have been indecisive; but in the third the Roman general suffered a complete defeat.