When Alexander the Great's successors, the Ptolemies, took control of Egypt in 323 BC, they began to actively promote trade with Mesopotamia, India, and East Africa through their ports on the Red Sea coast, as well as overland. This was assisted by the active participation of a number of intermediaries, especially the Nabataeans and other Arabs.

The Greeks were to remain in Central Asia for the next three centuries, first through the administration of the Seleucid Empire, and then with the establishement of the Greco-Bactrian Kingdom in Bactria. They kept expanding eastward, especially during the reign of Euthydemus (230-200 BC), who extended his control to Sogdiana, reaching and going beyond the city of Alexandria Eschate. 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 BC. The Greek historian Strabo writes that "they extended their empire even as far as the Seres (China) and the Phryni".

Chinese exploration of Central Asia

The next step came around 130 BC, with the embassies of the Han Dynasty to Central Asia, following the reports of the ambassador Zhang Qian (who was originally sent to obtain an alliance with the Yuezhi against the Xiong-Nu, in vain).

The Chinese emperor Wudi became interested in developing commercial relationship with the sophisticated urban civilizations of Ferghana, Bactria and Parthia.

The Chinese were also strongly attracted by the tall and powerful horses in the possession of the Dayuan (named "Heavenly horses"), which were of capital importance in fighting the nomadic Xiongnu. The Chinese subsequently sent numerous embassies, around ten every year, to these countries and as far as Seleucid Syria. The Chinese campaigned in Central Asia on several occasion, and direct encounters between Han troops and Roman legionnaires (probably captured or recruited as mercenaries by the Xiong Nu) are recorded, particularly in the 36 BC battle of Sogdiana (Joseph Needham, Sidney Shapiro). It has been suggested that the Chinese crossbow was transmitted to the Roman world on such occasions.

The Roman historian Florus also describes the visit of numerous envoys, included Seres (Chinese), to the first Roman Emperor Augustus, who reigned between 27 BCE and 14 CE.

The "Silk Road" essentially came into being from the 1st century BC, following these efforts by China to consolidate a road to the Western world and India, both through direct settlements in the area of the Tarim Basin and diplomatic relations with the countries of the Dayuan, Parthians and Bactrians further west.

A maritime "Silk Route" opened up between Chinese-controlled Jiaozhi (centered in modern Vietnam, near Hanoi) probably by the first century CE. It extended, via ports on the coasts of India and Sri Lanka, all the way to Roman-controlled ports in Egypt and the Nabataean territories on the northeastern coast of the Red Sea.

In 97 CE Ban Chao crossed the Tian Shan and Pamir mountains with an army of 70,000 men in a campaign against the Xiongnu (i.e., Huns). He went as far west as the Caspian Sea and the Ukraine, reaching the territory of Parthia, where he reportedly also sent an envoy named Gan Ying to Daqin (i.e., Rome). Gan Ying detailed an account of the western countries; although he likely reached only the Black Sea before turning back.

The Chinese army made an alliance with the Parthians and established some forts at a distance of a few days march from the Parthian capital Ctesiphon, planning to hold the region for several years. In 116 CE, the Roman Emperor Trajan advanced into Parthia to Ctesiphon and came within one day's march of the Chinese border garrisons, but no direct contacts are known.

The Roman Empire and silk - Menade in silk dress, Naples National Museum.Soon after the Roman conquest of Egypt in 30 BCE, regular communications and trade between India, Southeast Asia, Sri Lanka, China, the Middle East, Africa and Europe blossomed on an unprecedented scale. Land and maritime routes were closely linked, and novel products, technologies and ideas began to spread across the continents of Europe, Asia and Africa. Intercontinental trade and communication became regular, organised, and protected by the 'Great Powers.' Intense trade with the Roman Empire followed soon, confirmed by the Roman craze for Chinese silk (supplied through the Parthians), even though the Romans thought silk was obtained from trees.

The Senate issued, in vain, several edicts to prohibit the wearing of silk, on economic and moral grounds: the importation of Chinese silk caused a huge outflow of gold, and silk clothes were considered to be decadent and immoral.

The Hou Hanshu records that the first Roman envoy arrived in China by this maritime route in 166 CE, initiating a series of Roman embassies to China.