For six centuries Constantinople had been an impregnable bulwark against the forces of Islam. For nearly twice that space of time she had successfully resisted the menaces and attacks of the barbarians of the north--Goths, Huns, Avars, Russians, Bulgarians, Chazars--and had proudly defied the power of Chosroes, Timur, Bayazid, Harun-al-Rashid, and other leaders of savage hordes from Persia, Arabia, and Central Asia. Unlike Old Rome, which frequently opened her gates to invaders from the north of the Danube, New Rome never once yielded to her Teutonic and Slavonian foes. Although besieged more than a score of times between the fourth and the thirteenth century[54] she was able to withstand every assault however furious or long continued. And this she did after the vast empire which once extended from the Tigris to the Guadilquivir had been so reduced that little was left of it but the capital itself, which, at the time of its capture by the Turks under Mohammed II, was scarcely more than a besieged fortress. How the occupation of Constantinople by Mohammed the Conqueror, has complicated the political, military, and economic conditions of Europe for nearly five centuries is a matter of gloomy history. Owing to its matchless position it was long the natural center of the world’s commerce, the clearing house between Europe and Asia. Destined by nature itself to be the seat of two worlds, Constantinople must, as Freeman well observes, “remain the seat of imperial rule as long as Europe and Asia, as long as land and sea keep their places.”[55] The transfer of the capital of the Roman Empire from the Tiber to the Golden Horn, the foundation of Constantinople in 330 A. D., was one of the master-strokes in the history of civilization--indeed from the material and strategic point of view, I hold it to be the greatest. Rome, Paris, London, Vienna, Moscow, Madrid, Berlin, Washington, became capital cities by the gradual acts of the rulers in the course of years. But in ten years Constantinople remade the center of the civilized world. Nothing so stupendous in civic origins has ever been accomplished before or since, for its effects have been maintained with rare and partial breaks for eleven, nay, for fifteen centuries. The foundation of Alexandria by Alexander, of Antioch by Seleucus have some parallels. Mecca, Jerusalem, Cairo, Delhi have had fluctuating histories. Peter’s creation of Petrograd was a splendid mistake, which has ended in hideous failure. But the creation of Constantinople marks Constantine as one of the truly great, beside Julius, Trajan, Charles and Washington.[56] But more remarkable than anything that has yet been said of the Queen City of the Bosphorus is her marvelous continuity of imperial rule. From the time when Constantine transferred the capital of the empire from the Tiber to the Golden Horn, when, in the works of Dante, _Per cedere al Pastor si fece Greco,_[57]