In these many years of war, with frequent pauses for negotiation, Belisarius first comes into prominence as a commander. One noteworthy event, among others, is Mundhir’s great invasion of Syria. This Mundhir was the Arab vassal-prince of Hira, of the same line as the prince of the same name. He seems before this to have grown so powerful as to rouse Kavadh’s apprehensions, and the latter therefore deprived him, either wholly or in part, of his dominions for a time, in favour of Harith, a member of the much-ramified family of the Kinda kings. The statement that this event bore some relation to the Mazdakite troubles is hardly probable. On the outbreak of the war with Rome, however, Kavadh restored the whole of his former dominions to the tried warrior Mundhir. In the spring of 529 the latter invaded Syria, laid the whole country waste as far as Antioch, and carried off troops of captives that he might secure their ransom. He was a savage who in one day slaughtered four hundred nuns from a Syrian nunnery in honour of his goddess Zuhara (the planet Venus). In the same year his rival Harith went to war with him, and Mundhir caused a number of members of the princely family of Kinda, who had fallen into his hands, to be put to death at Hira. For half a century he was the terror of Roman subjects, troubling himself little to inquire whether peace prevailed or not, till at length he fell in battle against the Roman prince of the Arabs, Harith, the son of Jabala (June, 554), whose captive son he had likewise sacrificed to Zuhara. [Sidenote: [531-540 A.D.]] It was Mundhir who induced Kavadh, after an interval, to undertake a campaign in Syria itself (531). The Persians advanced far to the north along the right bank of the Euphrates, but were compelled to retreat by Belisarius. A battle was fought at Callinicus (Rakka), near the frontier that is, in which Belisarius was totally defeated; but the Persian commander was nevertheless obliged to return home. The Persians gained some successes in Mesopotamia the same year, and had almost reduced the great fortress of Martyropolis (Maiferkat, Arabic Mayafarikin) when tidings came of the death of the king, and brought about a truce. A few years before his death Kavadh had brought the Mazdakites to a horrible end. The sect seems to have grown so powerful that it could no longer be tolerated; for, in spite of all its theoretic idealism it threatened to subvert the foundations of society and the state. The catastrophe, which was accompanied by lavish bloodshed, took place in 528 or 529, under the orders of Prince Chosroes, acting in agreement with the king.