Nisibis (Persian Wars).
This fortress, known as the Bulwark of the East, was thrice besieged in 338, 346 and 350 by Sapor II, King of Persia. In the two former years he was compelled to retire after a siege of 60 and 80 days respectively. In 350 the city was defended by a garrison under Lucilianus, and Sapor, finding the ordinary methods unavailing, diverted the course of the Mygdonius, and by building dams formed a large lake, upon which he placed a fleet of armed vessels, and attacked the city almost from the level of the ramparts. Under pressure of the water a portion of the wall gave way, and the Persians at once delivered an assault, but were repulsed; and by the following day the garrison had rebuilt the wall. At the end of about three months, Sapor, having lost 20,000 men, raised the siege.