On the death of Ladislas, Matthew Corvinus, Hunyadi’s son, was elected by the Diet to succeed him (January 1458). Ragusa, which had been described by King Ladislas as the “scutum confiniorum regni nostri Dalmatiæ,” had been threatened by the Turks in 1455, but not seriously, as they were occupied elsewhere. In 1458 Mohammed again menaced the Republic, and sent Isak Beg into Bosnia to order the vassal princes to capture the city if she did not immediately make submission to him and increase her tribute.[404] Hungarian aid was solicited, and the citizens prepared to defend themselves; but once more the danger was averted, as the Turks had other more pressing matters to attend to. In 1459 the final conquest of Bosnia was begun. King Stephen Thomas had paid tribute to the Sultan since 1449, and after the fall of Constantinople he had sent envoys to do homage to the victor,[405] but at the same time he was imploring the help of the Pope; this caused much discontent among his Bogomil subjects, who had already shown themselves not unfriendly to the Turks. But after Hunyadi’s victory at Belgrad Stephen was encouraged to further resistance; he refused to pay the tribute, and actually intended to lead a crusade in person.[406] The Pope ordered his legate in Dalmatia to raise funds for him, and enjoined Kosača to help him.[407] Stephen began to attack the Turkish garrisons in Servia, but after taking a few towns he came to terms with the Sultan early in 1458, and paid him a tribute of 9000 ducats. On the death of Lazar, the Despot of Servia, the King of Hungary conferred the despotate on Stephen the Younger, or Tomašević, the Bosnian king’s son, who had married Lazar’s daughter, Helena. Thus Bosnia acquired the Danubian region of Servia, including Semendria. But Mohammed determined to conquer even these districts once for all, and to punish Stephen Thomas for his audacity. The Servians themselves were dissatisfied with their new ruler, because he was a devout Catholic, and they regarded him simply as a Hungarian viceroy. When in June 1459 Mohammed approached Semendria the inhabitants opened their gates to him. Owing to its position at the confluence of the Morava and the Danube it was the key to the whole country, and its fall, which spelt the end of Bosnian rule in Servia, caused consternation throughout Europe. It was attributed by Matthew Corvinus to Stephen Thomas and his son. While this quarrel was going on and the Hungarian king was at war with Germany, the Turkish general, Hassan Pasha, had obliged the King of Bosnia to let him pass through the country with a large army. The next year hostilities broke out between Paul Sperančić, Banus of Croatia, and Stephen Thomas, in the course of which the latter was killed. His son, Stephen Tomašević, succeeded to him, and was the last King of Bosnia (1461).