In 500 BC, the Persian Empire was the greatest empire the world had ever seen. Its territory stretched from the Indus River to the Black Sea and the coast of North Africa. Within its borders, the empire ruled over as much as 20% of the world’s population.
The empire contained dozens of formerly independent states and dozens of languages. Administering this massive realm required new systems of control than anything that had been used before. The Babylonians, Assyrians, Hittites and Egyptians had each controlled a small fraction of the territory now ruled by the Persians. To administer the empire, Cyrus the Great created and Darius I refined the division of the empire into 23 satrapies. Each satrap was a viceroy of the Shahanshah (“king of kings”) who ruled in the capital. The satraps exercised the authority of the king in governing and managing the provinces.
The satraps were not kings or vassal rulers, rather, they served at the pleasure of the Persian monarch. Administering the provinces, therefore, required the ability to send rapid communications between satraps and the capital. The king needed to be kept abreast of the situation in all parts of the empire in order to make well-informed decisions in a timely manner. Conversely, the king needed to be able to rapidly send orders back to different parts of the empire. If the satraps were given too much autonomy to take independent action without waiting for a word from the king, they could develop separatist tendencies and become rebellious. 
Previous empires in the ancient Near East had operated messenger systems for official business. The Assyrian mail system dated back to 1800 BC as evidenced by numerous letters found at Karum Kanesh in southeastern Anatolia. The Hittites and Egyptians also operated relay systems of messengers to transmit official business.
The more immediate antecedent, however, was the mail service of the neo-Assyrian empire. The Assyrians had built an empire larger than any that had come before, and therefore faced some of the same communications problems on a smaller scale which the Persians would later face. The Assyrians created a system of stations along major roads, situated about a day’s journey apart from each other where messengers could stop, rest and change horses. This relay system allowed messages to be rapidly carried throughout the empire. It took a courier from Nineveh only a few days to reach the Levant with a message.
First, the Persian Empire needed roads to enable communications. Previous civilizations had built plenty of roads to varying degrees of complexity, but no road network ran the distance of the Persian empire. Cyrus the Great’s solution to this problem was to connect segments of pre-existing roads into a massive highway which ran from Sardis on the Aegean coast of Anatolia to Susa, one of the four capital cities of the Persian Empire. Constructed in much the same way that smaller highways are expanded and connected to form interstates in the modern United States, the Persian highway was dubbed the Royal Road.
The Royal Road’s route can be traced based on the descriptions of it left by Herodotus as well as remains of ancient roads and bridges. Beginning in Sardis, the first sections were based on an earlier Phrygian road which ran across the central plains of Anatolia. From Phrygia, the road crossed the Halys River into Cappadocia. A “huge guardhouse” and gates were built at the river to control access to the road. The other end of the Cappadocian leg was guarded by two more guardhouses and accompanying gates. From there, the road crossed the great Euphrates and Tigris rivers and ran on to the Persian capital of Susa.
There was also a southern route which has been traced but was not mentioned by Herodotus and may have been added at a later date, which ran from Sardis through southern Anatolia, into Cilicia. This route passed through the Cilician Gates, a narrow mountain pass guarded by two massive fortresses. According to Xenophon, who traveled the southern route in 401 BC, “A river, called the Carsus, a hundred feet in breadth, runs between the two fortresses. The whole space between the fortifications was six hundred yards, and it was out of the question to force a way through, since the pass was narrow, and the walls extended to the sea, and above them were sheer cliffs.”
October 19, 2011 | Categories: Persian Period (539-330 BC), Spying and Intelligence, Technology | Tags: Anatolia, Artaxerxes II, Cilician Gates, Cunaxa, Cyrus the Great, Cyrus the Younger, Darius I, Herodotus, Mesopotamia, Persia, Postal Systems, Royal Road, Xenophon, Xerxes | 4 Comments »