Apart from a couple of exceptions, tributes were estimated in weighed silver, which was already the main currency of exchange. The fiscal unification of the empire brought to the unification of measure and value systems (or at least the imposition of one fiscal system over local systems). The peak of this unification was the spread of coinage, which made its first appearance in Lydia and Ionia. The gold and silver ‘daric’ soon became the official currency of the empire, being weighed metal whose weight and purity was guaranteed by the royal stamp. Coinage developed more as a response to administrative rather than commercial needs, such as the payment of taxes and tributes and the payment of mercenaries. Alongside imperial coins, other forms of payment and accounting continued to exist on a local level. However, with time, the issue of imperial coins brought to the issue of coins from other governors and cities. This development led to the commercial as well as the administrative and tributary use of coins.
The administrative, tributary, linguistic and monetary unification of the empire led to a material unification in terms of buildings and transports. Palaces and paradises were built throughout the empire. After all, satrapies had to be modelled upon the example of the empire’s original centre. In the areas characterised by a long history of urbanisation, building activities were conspicuous, but simply restored what was already there. In the Achaemenid period, then, both Sidon and Sardis received their unmistakable Persian traits, but simply replaced the previous (local or provincial) constructions. In contrast, throughout Iran and Central Asia, the consolidation of imperial control required the formation of new urban and palace centres, as well as agricultural infrastructures. This marked a definitive step towards the unification of the entire area to standards previously reserved for distinct areas.
Prior to Darius’ reign, a road network already existed to cater for the growing commercial interactions between regions. Moreover, in the previous empires (the Assyrian one in particular), this network was improved for military and administrative purposes. With Darius, however, this road network became increasingly more organic, with the designation of ‘royal roads’ (originally an Assyrian designation) to the main routes. These routes had resting stations equipped with fresh horses and fortresses protecting river crossings or mountain passes. A renowned contribution of Darius is his postal system, described with admiration by Herodotus for its efficiency and rapidity. Equally renowned are the interventions in road engineering, which expanded what was begun under the Assyrians and the Babylonians.
The Persians restored mountain roads and built fixed or pontoon bridges to cross rivers or even the sea (the Hellespont under Xerxes). From a Greek point of view, the main section of the Royal Road was the one linking Sardis to Susa. It crossed Anatolia, Armenia and Media. However, other sections must have been equally essential. For instance, an important road was the one going from Susa to Persepolis. Similarly, the Khorasan Highway from Babylon to Ecbatana and the Caspian Gates was the main route going north. The King’s Highway in Syria and the Transjordan plateau was the main route going south, meeting the South Arabian caravan routes. Finally, from a strictly Persian perspective, the routes linking Ecbatana with Bactria, or Persepolis with Drangiana and Arachosia must have been equally important to reach the far-eastern borders of the empire.
The consolidation of the empire’s road network developed alongside the consolidation of maritime routes. The previous mainland empires had long considered the Persian Gulf, the Red Sea and the Mediterranean Sea as branches of a circular Ocean encompassing and delimitating the known world. These branches penetrated towards the centre of the world, but remained separate from one another. The Ach-aemenid period constitutes the peak of a process of exploration. This process was begun by the Phoenicians (in the Mediterranean) and the Egyptians (in the Red Sea), who managed to link to each other the various internal branches of this Ocean. The circumnavigation of Africa and the excavation of a channel linking the eastern Nile to the Red Sea in Darius’ reign managed to improve the navigation of the Mediterranean and the Red Sea. Finally, the expedition of Scylax of Caryanda, who followed the course of the Indus River, reaching the Arabian Peninsula and the Isthmus of Suez, completed the circle.
The awareness of the connection between the Indus Valley and the river mouth of the Tigris and Euphrates certainly brought back an ancient route that had been vital at the time of Akkad and Meluhha. However, the discovery of the connection between Mesopotamia and Egypt through the circumnavigation of the Arabian Peninsula was even more important. Therefore, alongside the mainland caravan routes, south Arabia introduced maritime routes reaching Ethiopia on the one hand, and the Persian Gulf and India on the other. Classical sources tend to focus on the exploration of the Mediterranean. However, it is probable that the exploration of the Indian Ocean happened at the same time and with a similar intensity, though with completely different technical problems (such as monsoons and the ocean itself).
World History
