The entire empire, excluding Persia proper, was divided into twenty satrapies, or provinces, each one with its civil governor, or satrap. The satraps carried out the laws and collected the heavy tribute annually levied throughout the empire. In most of the provinces there were also military governors who commanded the army and reported directly to the king. This device of intrusting the civil and military functions to separate officials lessened the danger of revolts against the Persian authority. As an additional precaution Darius provided special agents whose business it was to travel from province to province and investigate the conduct of his officials. It became a proverb that "the king has many eyes and many ears." PERSIAN ROADS Darius also established a system of military roads throughout the Persian dominions. The roads were provided at frequent intervals with inns, where postmen stood always in readiness to take up a letter and carry it to the next station. The Royal Road from Susa, the Persian capital, to Sardis in Lydia was over fifteen hundred miles long; but government couriers, using relays of fresh horses, could cover the distance within a week. An old Greek writer declares with admiration that "there is nothing mortal more swift than these messengers." [14] UNION OF THE EAST UNDER PERSIA The political history of the East fitly ends with the three Persian conquerors, Cyrus, Cambyses, and Darius, who thus brought into their huge empire every great state of Oriental antiquity. Medes and Persians, Babylonians and Assyrians, Lydians, Syrians, and Egyptians--all were at length united under a single dominion. In the reign of Darius this united Orient first comes into contact with the rising power of the Greek states of Europe. So we may leave its history here, resuming our narrative when we discuss the momentous conflict between Persia and Greece, which was to affect the course, not alone of Persian or Greek, but of all European history. [15] [Illustration: Map, THE PERSIAN EMPIRE AT ITS GREATEST EXTENT (About 500 B. C.)] STUDIES 1. On the map Physical Map of Asia, section 7. Physical Asia, topic Grand Divisions of Asia, see what regions of Asia are less than 500 feet above sea level; less than 3000 feet; less than 9000 feet; less than 15,000 feet; over 15,000 feet. 2. On an outline map of the Orient indicate eight important rivers, two gulfs, three inland seas, the great plateaus and plains, the principal mountain ranges, two important passes, and the various countries and cities mentioned in this chapter. 3. On an outline map draw the boundaries of the Persian Empire under Darius, showing what parts were conquered by Cyrus, Cambyses, and Darius, respectively. 4. For what were the following places noted: Jerusalem; Thebes; Tyre; Nineveh; and Babylon? 5. For what were the following persons famous: Hammurabi; Rameses II; Solomon; Cyrus; Nebuchadnezzar; and Darius?