Constantine, brother of John, and afterwards the last emperor, had shown energy in the Morea. He was in possession of a large part of the Peloponnesus, and had chased the Turks out of Boeotia, Pindus, and part of Thessaly. This weakening of their hold compelled Murad to bestir himself. In November, 1446, he started for Greece at the head of an army of sixty thousand men. Constantine sent an ambassador, the historian Chalcondylas, to propose terms, which were, however, rejected. Murad then advanced and attacked Constantine, who held a strong position behind the famous rampart of the Hexamilion, extending across the Isthmus of Corinth. Murad carried it by assault, and killed all the garrison. His principal general then ravaged the Morea, and carried off sixty thousand Christians into slavery. Patras was captured and burnt, and Constantine, who had fought well but whose army was much smaller than the Turkish, had to pay tribute and surrender all territory that he had conquered from the Turks beyond the Isthmus of Corinth. He was still, however, able to retain possession of a large part of the Morea. [Sidenote: Iskender Bey and the Albanians.] After the campaign in Greece, Murad marched northwards to attack the Albanians, and endeavoured to capture Kroya,[155] the capital of the country. But it was held by the Albanian leader, George Castriotes, whom we have already met under the name of Iskender (or Alexander) Bey, a man who was a military genius, and who in some respects recalls the adventures and characteristics of Garibaldi. But he was unscrupulous as well as energetic. Devoting himself like a new Hannibal to the salvation of his country, he held and continued to hold absolute, but willingly rendered, sway during twenty-five years over the Albanian mountaineers. Christian by birth, but given over with his brothers to the Turks as hostages, and forcibly converted to Mahometanism, he had become a favourite of Murad for his handsome appearance, his strength of body, and his courage. He had gained power over his countrymen in the first instance by a ruse as bold as it was relentless. Scimitar in hand, he offered as an alternative to the reis-effendi, or commander-in-chief, either immediate death or the affixing of his signature and seal to a document ordering the governor of Kroya to hand over to him the fortress and the adjacent country. Having obtained the document in due form, he then killed the reis-effendi. At this time Iskender Bey was only nineteen years old. Gathering a small band of Albanians about him, he hastened across the peninsula and obtained possession of Kroya by a stratagem even more desperate and dangerous than that by which he had obtained the order for his appointment as Turkish governor. Leaving his followers outside the city and in hiding, he presented his credentials and obtained the keys of the fortress. During the night, he personally admitted his followers, and the Turkish garrison were murdered while they slept.