We must now return to Stephen Kosača, Duke of St. Sava, and his relations with Ragusa. Like so many other Servian princes he was a Bogomil by religion, and when Stephen Thomas, King of Bosnia, abjured that heresy and became a Catholic, many of his Bogomil subjects fled into the Duchy to escape persecution, and others into Turkish territory, while his Orthodox subjects took refuge in Servia. This caused further discords between Bosnia and Servia, and John Hunyadi cannot be exempted from the blame of having induced Stephen Thomas to ill-treat the heretics;[391] in fact he actually quarrelled with the King because the latter relented from his persecutions. The King’s daughter had married Stephen Kosača, who nominally was a vassal of Bosnia, but he hardly recognised his allegiance at all, and styled himself “by the Grace of God Duke of St. Sava, Lord of Hlum and the Littoral, Grand Vojvod of the Bosnian kingdom, Count of the Drina,” &c.[392] Like his predecessor Sandalj Hranić, he was one of the fatal men of the Balkans; although he tried to resist them later, his attitude contributed not a little to the Turkish conquest of the South Slavonic lands. His aim was simply to consolidate and extend his own dominions at the expense of his neighbours, and he availed himself for this purpose of the assistance which the Turks were always only too ready to give. He also proved Ragusa’s most inveterate enemy. In July 1450 he was still on good terms with the Republic,[393] but in 1451 the first dispute arose. The cause, according to Chalcocondylas, and repeated by Razzi, Gondola, and others, was that he had taken to himself a Florentine mistress brought into the country by some Italian merchants, and drove his wife Helen from the Court. She repaired with her son to Ragusa, and the Duke demanded that they should be given up. The Republic refused, and Kosača, out of revenge, raised duties on Ragusan trade, opened salt-markets in the Narenta, reoccupied part of Canali, and laid waste the Republic’s territory. A more likely reason is probably to be found in Kosača’s overmastering ambition. The Republic at once demanded help of the Christian Powers, especially of Hungary, against the heretical Duke, and an envoy was sent to the Pope to complain that many Italians were in his service. His Holiness replied by forbidding all good Catholics from having anything to do with him. Fortunately for Ragusa the King of Bosnia was hostile to Kosača on account of the indignities to which the latter had subjected his wife (the King’s daughter). For the same reason his son Vladislav left Ragusa and raised a rebellion against his father, allying himself with the Republic, to whom he promised to give back Canali as soon as he was master of the Duchy.[394] In December 1451 Ragusa contracted an alliance with Stephen Thomas, who undertook “to declare war without delay and carry it on without interruption against the Duke Stephen