Dagisthseus, the Roman commander, besieged it with his entire force of eight thousand men, and succeeded by his constant attacks in reducing the garrison to little more than a fourth of its original number.

Baffled in one attempt to effect a breach by means of a mine, he had contrived to construct another, and might have withdrawn his props, destroyed the wall, and entered the place, had he not conceived the idea of bargaining with the emperor for a specific reward in case he effected the capture.

Whilst he waited for his messenger to bring a reply, the Persian general, Memeroes, forced the passes from Iberia into Lazica, and descended the valley of the Phasis with an army of 30,000 men.

Dagisthalus in alarm withdrew, and Petra was relieved and revictualled.

The walls were repaired hastily with sandbags, and the further defence was entrusted to a fresh garrison of 3000 picked soldiers.