When, in the spring of 1389, Murad found himself ready to exact vengeance for Plochnik, and started from Bulgaria on his punitive expedition, he was joined by Constantine of Kustendil, by the Serbian Dragash, to whom he had given Serres as fief, and even by the sons of Vukasin, the Serbian kral who had been killed in 1371 at Cernomen.[409] Balsa, prince of Zenta (upper Albania), postponed his march to join the allies, and entered secretly into correspondence with Murad through a Serbian nobleman in the Ottoman camp. Lazar knew of this treachery. He knew also that some of his own lieutenants had in all probability arranged to sell him out to the Ottoman emir.[410] Kossovapol, the plain of the blackbirds, is the name given to the valley of the Sitnika River (an upper tributary of the Morava) west of Pristina and south of Mitrovitza.[411] Here the decisive battle for Serbian independence was fought on June 20, 1389.[412] Serbian chronicles state that Murad had enjoined upon his soldiers that they should neither destroy nor sack the rich castles, villages, and cities of this region after the battle. Only four castles in all were destroyed.[413] This command shows that Murad was confident of the outcome. He was fighting for the possession of this country, for the wealth and the prestige that it would give him. He had no intention of destroying what he knew would be his to enjoy, nor did he desire to alienate the Serbian peasantry by unnecessary harshness. Here, as elsewhere, new Osmanlis rather than Ottoman subjects were the _desiderata_: they could be won only by kindness. Since the clemency of the Osmanlis in dealing with the vanquished after the battle is frankly recorded by the Serbians themselves, we cannot doubt that the wise and far-seeing provisions of the conqueror were carried out. Of Kossova much has been written. It was the culminating event in that legendary period of Serbian history which had begun fifty years before with the exploits of Stephen Dushan. Lazar, Serbian chieftain with no long line of royal ancestors behind him, with no great weight of authority among his contemporaries, who began his career by craven submission to Murad and, after eighteen years in which no deed to his credit is recorded, survived a crushing defeat to be executed on the field of battle--this is the Charlemagne of Serbian poetry. On the anniversary of Kossova, the Serbians pray for his soul. As a saint, he gets many more candles at his shrine than his namesake of Bethany who was raised from the dead. Such is legend in history. But what amazes one is the curious fact that the very folksongs that glorify Saint Lazar and lament Kossova reveal a frank and true picture of the events, and prove how little warrant there is for the legend!