<P> By the time of Herodotus (c. 475 BCE), the Royal Road of the Persian Empire ran some 2,857 km (1,775 mi) from the city of Susa on the Karun (250 km (155 mi) east of the Tigris) to the port of Smyrna (modern İzmir in Turkey) on the Aegean Sea . It was maintained and protected by the Achaemenid Empire (c. 500--330 BCE) and had postal stations and relays at regular intervals . By having fresh horses and riders ready at each relay, royal couriers could carry messages and traverse the length of the road in nine days, while normal travellers took about three months . </P> <P> The next major step in the development of the Silk Road was the expansion of the Greek empire of Alexander the Great into Central Asia . In August 329 BCE, at the mouth of the Fergana Valley in Tajikistan across the mountain pass from the modern Chinese province of Xinjiang, Alexander founded the city of Alexandria Eschate or "Alexandria The Furthest". This later became a major staging point on the northern Silk Route . See Dayuan (Ta - yuan; Chinese: 大 宛; literarily "Great Ionians"). </P> <P> The Greeks remained in Central Asia for the next three centuries, first through the administration of the Seleucid Empire, and then with the establishment of the Greco - Bactrian Kingdom (250--125 BCE) in Bactria (modern Afghanistan, Tajikistan, and Pakistan) and the later Indo - Greek Kingdom (180 BCE--10 CE) in modern Northern Pakistan and Afghanistan . They continued to expand eastward, especially during the reign of Euthydemus (230--200 BCE), who extended his control beyond Alexandria Eschate to Sogdiana . There are indications that he may have led expeditions as far as Kashgar in Chinese Turkestan, leading to the first known contacts between (China and the West around 200 BCE . The Greek historian Strabo writes, "they extended their empire even as far as the Seres (China) and the Phryni ." </P> <P> The Hellenistic world and Classical Greek philosophy mixed with Eastern philosophies, leading to syncretisms such as Greco - Buddhism . </P>

What impact did the indian ocean trade have on southern china