John VI. passed away in 1448, and Sultan Murad in 1451. The one was succeeded by his brother Constantine, the last Christian sovereign of Byzantium, the other by his young son Mohammed the Conqueror. Constantine was a Romanist like his elder brother, and was therefore treated with great suspicion and coolness by his handful of subjects. He was the best man that the house of Paleologus had ever reared, brave, pious, generous, and forgiving. Like King Hosea of Israel, “he did not evil as the kings that were before him,” yet was destined to bear the penalty for all the sins and follies of his long line of predecessors. Mohammed II., the most commanding personality among the whole race of Ottoman Sultans, set his heart from the first on seizing Constantinople, the natural centre of his empire, and making it his capital. Some excuse had to be found for falling on his vassal: the one that he chose was a rather unwise request which Constantine had made. There dwelt at Constantinople a Turkish prince of the royal house named Orkhan, for whom Mohammed paid a considerable subsidy, on condition that he was kept out of the way of mischief and plotting. Some unhappy inspiration impelled Constantine to ask for an increase in the subsidy, and to hint that Orkhan had claims to the Sultanate. This was excuse enough for Mohammed: without taking the trouble to declare war he sent out troops and engineers, and began to erect forts on Greek soil, only four miles away from Constantinople, at the narrowest point of the Bosphorus, so as to block the approach to the city from the Black Sea. The Emperor did not dare to remonstrate, but when the Turks began to pull down a much-venerated church, in order to utilize its stones in the new fort, a few Greeks took arms and drove the masons away. They were at once cut down by the Turkish guards: Constantine demanded redress, and then Mohammed, having fairly picked his wolf-and-lamb quarrel with his unfortunate vassal, commenced open hostilities [Autumn 1452]. Turkish light troops at once appeared to blockade the city while the Sultan began to collect a great train of cannon at Adrianople, and to build a large fleet of war galleys in the ports of Asia: the siege was to begin in the ensuing spring.