The Roman Empire was a trading empire as well as a military empire, and Roman money was widely recognized throughout the region, and beyond. Latin became the language of the educated elite of the entire empire and of government offi cials and soldiers who settled in various parts of the empire. Gradually, Greek began to supplant Latin in the eastern Mediterranean, and it became the language of business and commerce in the eastern part of the Roman Empire.
Surviving tombstones show that many Romans came from distant lands. Goods were traded extensively-Rome had to import large amounts of corn and wheat to feed its growing population. Ideas also traveled throughout the Roman Empire. Initially these were connected with the Pax Romana–the Roman legal system. Under Antoninus Pius, Roman citizenship was extended in much of the eastern Mediterranean, and Roman citizens had to be tried in a Roman court, leading to Roman law becoming the standard in the eastern part of the empire. The Romans encouraged the spread of learning, philosophy, and religion. Christianity and the belief in Mithras rapidly spread to all corners of the empire, with archaeological evidence for both religions stretching from Spain to northern England and to the Middle East. Since the founding of Rome, the citizenry had traded with other empires. Roman goods found their way to the Kushan Empire in southern Pakistan and Afghanistan. The Sogdians, in Central Asia (modern-day Uzbekistan), traded with both the Romans and the Chinese, and Roman coins have been found in archaeological sites in some parts of the Far East.

I. Sino-Roman relations

Sino-Roman relations comprised the mostly indirect contact, flow of trade goods, information, and occasional travellers between the Roman Empire and Han Empire of China, as well as between the later Eastern Roman Empire and various Chinese dynasties. These empires inched progressively closer in the course of the Roman expansion into the ancient Near East and simultaneous Han Chinese military incursions into Central Asia. Mutual awareness remained low, and firm knowledge about each other was limited. Only a few attempts at direct contact are known from records. Intermediate empires such as the Parthians and Kushans, seeking to maintain lucrative control over the silk trade, inhibited direct contact between these two Eurasian powers. In 97 AD, the Chinese general Ban Chao tried to send his envoy Gan Ying to Rome, but Gan was dissuaded by Parthians from venturing beyond the Persian Gulf. Several alleged Roman emissaries to China were recorded by ancient Chinese historians. The first one on record, supposedly from either the Roman emperor Antoninus Pius or his adopted son Marcus Aurelius, arrived in 166 AD. Others are recorded as arriving in 226 and 284 AD, with a long absence until the first recorded Byzantine embassy in 643 AD.

In classical sources, the problem of identifying references to ancient China is exacerbated by the interpretation of the Latin term Seres, whose meaning fluctuated and could refer to several Asian peoples in a wide arc from India over Central Asia to China. In Chinese records, the Roman Empire came to be known as Daqin or Great Qin. Daqin was directly associated with the later Fulin (拂菻) in Chinese sources, which has been identified by scholars such as Friedrich Hirth as the Byzantine Empire. Chinese sources describe several embassies of Fulin arriving in China during the Tang dynasty and also mention the siege of Constantinople by the forces of Muawiyah I in 674–678 AD.

Geographers in the Roman Empire such as Ptolemy provided a rough sketch of the eastern Indian Ocean, including the Malay Peninsula and beyond this the Gulf of Thailand and South China Sea. Ptolemy’s Cattigara was most likely Óc Eo, Vietnam, where Antonine-era Roman items have been found. Ancient Chinese geographers demonstrated a general knowledge of West Asia and Rome’s eastern provinces. The 7th-century AD Byzantine historian Theophylact Simocatta wrote of the contemporary reunification of northern and southern China, which he treated as separate nations recently at war. This mirrors both the conquest of Chen by Emperor Wen of Sui (reigned 581–604 AD) as well as the names Cathay and Mangi used by later medieval Europeans in China during the Mongol-led Yuan dynasty and Han-Chinese Southern Song dynasty.

Beginning in the 1st century BC with Virgil, Horace, and Strabo, Roman histories offer only vague accounts of China and the silk-producing Seres people of the Far East, who were perhaps the ancient Chinese. The 1st-century AD geographer Pomponius Mela asserted that the lands of the Seres formed the centre of the coast of an eastern ocean, flanked to the south by India and to the north by the Scythians of the Eurasian Steppe. The 2nd-century AD Roman historian Florus seems to have confused the Seres with peoples of India, or at least noted that their skin complexions proved that they both lived “beneath another sky” than the Romans. Roman authors generally seem to have been confused about where the Seres were located, in either Central Asia or East Asia. The historian Ammianus Marcellinus (c. 330 – c. 400 AD) wrote that the land of the Seres was enclosed by “lofty walls” around a river called Bautis, possibly a description of the Yellow River.

The existence of China was known to Roman cartographers, but their understanding of it was less certain. Ptolemy’s 2nd-century AD Geography separates the Land of Silk (Serica) at the end of the overland Silk Road from the land of the Qin (Sinae) reached by sea. The Sinae are placed on the northern shore of the Great Gulf (Magnus Sinus) east of the Golden Peninsula (Aurea Chersonesus, Malay Peninsula). Their chief port, Cattigara, seems to have been in the lower Mekong Delta. The Great Gulf served as a combined Gulf of Thailand and South China Sea, as Marinus of Tyre and Ptolemy’s belief that the Indian Ocean was an inland sea caused them to bend the Cambodian coast south beyond the equator before turning west to join southern Libya (Africa). Much of this is given as unknown lands, but the north-eastern area is placed under the Sinae.