Thus we find some of the Palæologi, Comneni, Lascaris, and Cantaconzeni, and learned men like John Lascaris, Chalcocondylas, Emmanuel Marulus, Theodore Spandukinos, author of a history of the Turks, Paul Tarchaniotes, father of the historian John, and many others. No doubt these men contributed to the revival of learning in Dalmatia, as they did in the Italian towns. The refugees were provided with food, shelter, and money, and were afterwards sent on board Ragusan galleys free of charge to Ancona.[400] The citizens would have been willing that they should settle permanently at Ragusa, but the Senate feared that as many of them were such distinguished men the Sultan might use this as a pretext for aggression. A certain number, however, did remain. After the capture of Constantinople it was hoped that Mohammed would content himself with being overlord of the remaining Balkan lands not under his direct sway. But he soon evinced more dangerous intentions, and proceeded to establish his complete ascendency, destroying all the independent or semi-independent States. Of these the first to be attacked was Servia, which the Sultan claimed through his stepmother, a Servian princess. The miserable remnant of the great Tsar Dušan’s Empire was reduced to a small part of the present kingdom of Servia. Mohammed’s object was to prepare for the struggle with Hungary, the only Power which he seriously feared, for Genoa was now weak, and Venice’s first thought was “not to recover the bulwark of Christendom from the hands of the Muslim, but to preserve her own commercial privileges under the Infidel ruler.”[401] In 1454 the Turks invaded Servia, captured Ostrovica, and besieged Smederevo (Semendria); but John Hunyadi led an army against them, relieved that stronghold, defeated them at Kruševac, and burnt the fortress of Vidin on the Danube. But the following year Mohammed advanced in person and captured Novobrdo,[402] with its valuable mines, “Totam religionem Christianam libidinoso ambiciosoque animo dicioni suæ ascripsit, flagratque cupidine mundi,” as the Ragusan reports informed the Hungarian king. The Republic suffered ill-effects from this capture, because the Ragusan merchants who had a flourishing trade there were driven out. In July 1456 Mohammed besieged Belgrad, but was defeated by the courage of the defenders aided by the brilliant strategy of Hunyadi. Unfortunately this great leader died soon afterwards, and Hungary was crippled by internal troubles. In 1457 Fra Marino da Siena travelled through Dalmatia to preach a crusade against the Turks and collect money for that purpose. He raised 4000 ducats at Ragusa alone,[403] and the King of Hungary requested the Senate to use its influence to induce him to devote the money to a land crusade, as the danger on that side was more pressing, rather than to a naval expedition. By the end of the year the whole of Servia was subjugated except Belgrad and the Danubian provinces.