What followed would be incredible were it not a matter of history. These fifteen ships were immediately swallowed up by the huge fleet of the enemy, but under the superb leadership of Theophanes each one fought with the fury of desperation. They had one hope, the weapon that had twice before saved the city, Greek fire. The Russians swarmed alongside only to find their ships taking fire with a flame that water would not quench. Contempt of their feeble enemy changed soon to a wild terror. There was but one impulse, to get out of reach of the Christians, and the ships struggled to escape. Soon the whole Russian fleet was in wild flight with the gallant fifteen in hot pursuit. Some of these could make but slow headway because of their unseaworthiness, but when all was over the Russians are said to have lost two-thirds of their entire force. The invaders who had been left on shore were then swept into the sea by reenforcements that had arrived at Constantinople, and not a vestige was left of the Russian invasion. Once more Greek fire and the Christian navy had saved the empire; and for sheer audacity, crowned with a victory of such magnitude, the feat of Theophanes stands unrivaled in history. From the tenth century on, Constantinople began to find her rivalries in the west. The coronation of Charlemagne in 800 had marked the final separation of the eastern and the western empire. As noted above, the passing of the Saracens gave opportunity for the growth of commercial city-states like Genoa, Pisa and Venice, and their interests clashed not only with one another but also with those of Constantinople. The climax came in 1204 when Venice succeeded in diverting the Fourth Crusade to an expedition of vengeance for herself, first against the city of Zara and then against Constantinople. This time the Eastern Empire had no fleet ready for defense and the Venetian galleys filled the waters under the city walls. Many of these galleys were fitted with a kind of flying bridge, a long yard that extended from the mast to the top of the wall and stout enough to bear a file of men that scrambled by this means to the parapets. After many bloody repulses the city was finally captured, and there followed a sack that for utter barbarity outdid anything ever perpetrated by Arab or Turk. Thus the city that for nearly a thousand years had saved Christian civilization was, by a hideous irony of fate, taken and sacked by a Crusading army.