The Hungarians recovered their strength after Varna and Hunyadi was able to lead another expedition down the Danube. Turkish counter-attacks saw this "crusade" driven back. After Murad dealt with the Greeks at the Peloponesse and others who had fought him at Varna, he turned his attention to Albania, whose leader, once an Ottoman hostage, was now a popular resistance leader. Hunyadi could not refuse an offer to fight the Turks and in 1448 an army of some 24,000 Hungarians marched south into Serbia. At the Second Battle of Kosovo Murad scored another victory against the Hungarians. This time, Hunyadi had had enough and was unable to campaign against the Ottoman Sultan. Murad II passed on his powers to his successor, Mehmed II. Thanks to such victories, the Ottoman forces were able to capture Constantinople in 1453 with only the Italians offering minimal support to the Byzantines.