At Hit the rolling Assyrian plain had come to an end, and the invading army had entered upon the low alluvium of Babylonia, a region of great fertility, intersected by numerous canals, which in some places were carried the entire distance from the one river to the other.

The change in the character of the country encouraged the Persians to make a change in their tactics.

Hitherto they had been absolutely passive; now at last they showed themselves, and commenced the active system of perpetual harassing warfare in which they were adepts.

A surena, or general of the first rank, appeared in the field, at the head of a strong body of Persian horse, and accompanied by a sheikh of the Saracenic Arabs, known as Malik (or "King") Rodoseces.

Retreating as Julian advanced, but continually delaying his progress, hanging on the skirts of his army, cutting off his stragglers, and threatening every unsupported detachment, this active force changed all the conditions of the march, rendering it slow and painful, and sometimes stopping it altogether.