Next, in response to the Byzantine appeal for help against the Ottoman advance, Philip instructed de Thoisy to lead his squadron to reinforce a squadron of four galleys built or hired at Nice and Venice, commanded by Waleran de Wavrin, to join Pope Eugene IV's planned Crusade. De Wavrin's four galleys sailed in July 1444 but failed to stop Murad II's Anatolian army from crossing the Bosporus. De Thoisy joined de Wavrin's squadron at Constantinople, where the latter had gone to spend the winter. In the meantime, the crusading army led by Wladyslaw III of Poland (Ulaszlo I as king of Hungary) and Janos Hunyadi had been severely defeated by the united Anatolian and Rumelian armies of Murad II, on 10 November 1444, on the plain before Varna, on the coast of the Black Sea. In the spring of 1445, de Wavrin sailed to the Danube to join the Hungarians in the continuing Crusade, while de Thoisy took his ships along the south coast of the Black Sea.