The levy of children was regarded by the Christians as a blood tax of a terrible kind. The corps thus formed was a most valuable instrument in the hands of Sultans who were strong enough to control it. But later, in the times of degenerate Sultans, it became a kind of Prætorian Guard. It dictated the deposition of Sultans and the nomination of their successors. It often insisted on a policy of war. In 1648, under Mahomet IV, the restriction of the force to Christian children was removed, and the sons of Janissaries and other Moslems were admitted. Later the levy of Christian children was abandoned, and none but sons of Moslems were admitted to the corps. After the time of Solyman its numbers were greatly increased. It became a danger to the State. It will be seen that in 1826 Mahmoud II took vengeance on it for the humiliations he and previous Sultans had undergone, and extinguished it in ruthless scenes of blood. There cannot be a doubt, however, that Murad, by creating this corps of Janissaries and recruiting it from the Christian population in Europe, forged a weapon which for two hundred years to come played a dominant part in the aggrandizement of the Ottoman Empire. Knolles, in his graphic history of the Turkish Empire, sums up the character of Murad in the following sentences, which could not be improved upon:— Murad was more zealous than any other of the Turkish kings; a man of great courage and in all his attempts fortunate; he made greater slaughter of his enemies than both his father and grandfather; his kingdom in Asia he greatly enlarged by the sword, marriage, and purchase; and using the discord and cowardice of the Grecian princes to his profit, subdued a great part of Thracia, with the territories adjoining thereto, leaving unto the Emperor of Constantinople little or nothing more in Thracia than the imperial city itself, with the bare name of an emperor almost without an empire; he won a great part of Bulgaria and entered into Serbia, Bosnia, and Macedonia; he was liberal and withal severe; of his subjects both beloved and feared; a man of very few words, and one that could dissemble deeply.[7] IV BAYEZID I 1389-1403 BAYEZID succeeded his father, Murad, at the age of thirty-four. He reigned as Sultan for only fourteen years, the last of which was spent in captivity. No one of the Othman race passed through such vicissitudes, with such a brilliant career of victory during nearly the whole of his reign, but ending with overwhelming and crushing defeat. He had all the courage and military capacity of his three predecessors. He excelled them greatly in cruelty and brutality. In his private life he descended to depths of sensuality and unmentionable and degrading vice which were unknown to them.