In 1361, when Lorenzo Celsi was elevated to the dogeship of Venice, the Senate had made overtures to John Palaeologos for an alliance against Murad.[277] This plan was frustrated by the successes of the Osmanlis in Thrace. The Venetians held back, and allowed John to suffer the humiliation of signing the treaty that made him a vassal of Murad. In the crusade that ended in the disaster of the Maritza, the Venetian participation was half-hearted, and it proved valueless. The Venetians were not even on hand to prevent Murad from crossing the Dardanelles. In fact, there is every reason to believe that they now began to look upon the Osmanlis as a valuable tool in checkmating the ambition of Louis of Hungary to inherit the shortlived empire of Stephen Dushan.[278] When he saw that Murad had come into Thrace to stay, and that there was no hope from the Venetians, John Palaeologos turned to the Hungarians. He made a secret visit to Buda to enlist the aid of Louis, and made the usual promise that the Byzantines would return to the Roman fold.[279] On his return he passed through the principality of Sisman, who had just inherited the lower portion of Bulgaria. Sisman, either at the suggestion of Andronicus Palaeologos, who wanted to succeed his father, or in the hope of winning favour with Murad, detained the emperor in the fortress of Nicopolis on the Danube.[280] Amadeo VI of Savoy was one of the princes who had taken the cross from Pope Urban V at Avignon on Holy Friday, 1363, for the crusade that never materialized. The receipt of a letter from Louis of Hungary, informing him of the imprisonment of his cousin (John’s mother was a princess of Savoy), and pointing out the rapid spread of Ottoman power, caused Amadeo to yield to the Pope’s continued and urgent solicitations.[281] With some fifteen hundred soldiers, he embarked for the East on fifteen galleys. After a stop at Negropont and Mitylene to get reinforcements, Amadeo entered the Hellespont, and captured Gallipoli without difficulty. The Osmanlis fled by night, abandoning the fortress.[282] But the Savoyards made no attempt to follow up this victory, or even to keep Gallipoli. Instead of attacking the infidels, they sailed into the Black Sea, and started a vigorous campaign against the Bulgarians. Sozopolis and Burgas were captured, and several other important fortresses to the north. The bravery of the crusaders was rivalled only by their cruelty. Their bloodlust made such an impression upon the Bulgarians that they wanted nothing to do with Franks bearing the cross. When the Savoyards laid siege to Varna, Sisman gave up his prisoner to save the city.