Another menace to the Eastern Empire was from the Italians, who were represented by large colonies throughout the imperial territories, and even in the capital itself, where they enjoyed for a time exceptional privileges, such as being directly governed by their own ambassadors, having favored rates of tariff on their commerce, often amounting to free trade, and at times receiving high appointments in the service of the empire. Yet these prosperous conditions were frequently interrupted by quarrels with the Greeks, reaching on occasions to civil war within the walls of the capital. Pisan and Genoese pirates ravaged the Ægean, and even blockaded the Dardanelles against the passage of Greek ships. In 1198 these freebooters defeated the imperial navy. Venice, however, was the most formidable of these rivals for power within the empire, as she had been at times the most favored nation. In 1171 the Venetians attacked Dalmatia and pillaged the Ægean, until they were forced by herculean efforts of the Greek government to sue for peace. Henry Dandolo conducted the mission for treaty, and during his stay in Constantinople became blind. It is asserted by the Venetians that his affliction was due to torture perpetrated upon him by command of the emperor. It was a common practice of the Greeks to destroy the sight of those they would render impotent to do them harm. This ancient punishment was called abacination; the process was that of forcing the victim to gaze into a basin of highly polished metal, which by its shape concentrated the rays of sunlight and constituted a burning-mirror. Whether this is the true explanation of his blindness or not, it is certain that Dandolo ever after displayed an absorbing passion to wreak vengeance upon the Greek power, and we shall find him foremost among its foes in the fatal expedition called the fourth crusade. But, aside from these inducements, the wealth of the city offered to the covetous a prize second to none in the world. The situation of Constantinople on the narrow highway of the Bosporus or Strait of St. George, which connects the Black Sea with the Mediterranean, made it mistress of the maritime commerce between Europe and Asia. Neighboring countries contributed by their very geographical relation to the power on the Bosporus. The Balkan peninsula, terminating in the classic land of Greece, and fringed with the islands of the Ægean and the Adriatic; the eastern provinces of Europe, drained by the Danube, whose mouth was hard by; Russia from the Siberian snows to the temperate climate of the Euxine; Asia Minor, the seat of ancient civilization in the middle Orient, even to the entrance of Persia; the Holy Land, and the fertile valley of the Nile—each of these, in extent and population enough for an empire, and all of them lying in easy accessibility, fitted Constantinople to be the natural capital of the greatest power in the world.