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

The indirect exchange of goods on land along the Silk Road and sea routes involved (for example) Chinese silk, Roman glassware and high-quality cloth. Roman coins minted from the 1st centuryAD onwards have been found in China, as well as a coin of Maximian (Roman emperor from 286 to 305AD) and medallions from the reigns of Antoninus Pius () and Marcus Aurelius () in Jiaozhi (in present-day Vietnam), the same region at which Chinese sources claim the Romans first landed. Roman glassware and silverware have been discovered at Chinese archaeological sites dated to the Han period (202BC to 220AD). Roman coins and glass beads have also been found in the Japanese archipelago.

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 the Chinese records from the Han dynasty onwards, the Roman Empire came to be known as Daqin or Great Qin. The later term Fulin () has been identified by Friedrich Hirth and others as the Eastern Roman (Byzantine) Empire. Chinese sources describe several embassies of Fulin (Byzantine Empire) arriving in China during the Tang dynasty (618–907AD) and also mention the siege of Constantinople by the forces of Muawiyah I in 674–678AD.

Geographers in the Roman Empire, such as Ptolemy in the second centuryAD, provided a rough sketch of the north-eastern Indian Ocean, including the Malay Peninsula and beyond this the Gulf of Thailand and the 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 of Rome's eastern provinces. The 7th-centuryAD Byzantine historian Theophylact Simocatta wrote of China's reunification under the contemporary Sui dynasty (581 to 618AD), noting that the northern and southern halves were separate nations recently at war. This mirrors both the conquest of Chen by Emperor Wen of Sui () as well as the names Cathay and Mangi used by later medieval Europeans in China during the Mongol-led Yuan dynasty (1271–1368) and the Han Chinese-led Southern Song dynasty (1127–1279).

Geographical accounts and cartography Roman geography

Beginning in the 1st century BC with Virgil, Horace, and Strabo, Roman historians offer only vague accounts of China and the silk-producing Seres people of the Far East, who were perhaps the ancient Chinese.Lewis (2007), p. 143. 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.Ostrovsky (2007), p. 44. Roman authors generally seem to have been confused about where the Seres were located, in either Central Asia or East Asia.Schoff (1915), p. 237. The historian Ammianus Marcellinus () 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 () at the end of the overland Silk Road from the land of the Qin (Sinae) reached by sea.Yule (1915), pp. 1–2, 11. The Sinae are placed on the northern shore of the Great Gulf () east of the Golden Peninsula (, Malay Peninsula). Their chief port, Cattigara, seems to have been in the lower Mekong Delta. The Great Gulf served as a combined Gulf of Tonkin 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).Raoul McLaughlin (2010), pp. 58–59.Suárez (1999), p. 92. Much of this is given as unknown lands, but the north-eastern area is placed under the Sinae.Wilford (2000), p. 38; Encyclopaedia Britannica (1903), p. 1540.

Classical geographers such as Strabo and Pliny the Elder were slow to incorporate new information into their works and, from their positions as esteemed scholars, were seemingly prejudiced against lowly merchants and their topographical accounts. Ptolemy's work represents a break from this, since he demonstrated an openness to their accounts and would not have been able to chart the Bay of Bengal so accurately without the input of traders.Parker (2008), p. 118. In the 1st-century AD Periplus of the Erythraean Sea, its anonymous Greek-speaking author, a merchant of Roman Egypt, provides such vivid accounts of eastern trade cities that it is clear he visited many of them. These include sites in Arabia, Pakistan, and India, including travel times from rivers and towns, where to drop anchor, the locations of royal courts, lifestyles of the locals and goods found in their markets, and favourable times of year to sail from Egypt to these places to catch the monsoon winds.Schoff (2004) , Introduction. Retrieved 19 September 2016. The Periplus also mentions a great inland city, Thinae (or Sinae), in a country called This that perhaps stretched as far as the Caspian. The text notes that silk produced there travelled to neighbouring India via the Ganges and to Bactria by a land route. Marinus and Ptolemy had relied on the testimony of a Greek sailor named Alexander, probably a merchant, for how to reach Cattigara (most likely Óc Eo, Vietnam). Alexander (Greek: Alexandros) mentions that the main terminus for Roman traders was a Burmese city called Tamala on the north-west Malay Peninsula, where Indian merchants travelled overland across the Kra Isthmus to reach the Perimulic Gulf (the Gulf of Thailand). Alexandros claimed that it took twenty days to sail from Thailand to a port called "Zabia" (or Zaba) in southern Vietnam.McLaughlin (2014), p. 205.Suárez (1999), p. 90. According to him, one could continue along the coast (of southern Vietnam) from Zabia until reaching the trade port of Cattigara after an unspecified number of days (with "some" being interpreted as "many" by Marinus). More generally, modern historical scholars assert that merchants from the Eastern part of the Roman Empire were in contact with the peoples of China, Sri Lanka, India and the Kushana Empire.

Cosmas Indicopleustes, a 6th-century AD Eastern Roman (Byzantine) Greek monk from Alexandria and former merchant with experience in the Indian Ocean trade, was the first Roman to write clearly about China in his Christian Topography ( 550 AD).Yule (1915), p. 25. He called it the country of Tzinista (comparable to Sanskrit Chinasthana and Syriac Sinistan from the 781 AD Nestorian Stele of Xi'an, China), located in easternmost Asia.Yule (1915), p. 28.Lieu (2009), p. 227. He explained the maritime route towards it (first sailing east and then north up the southern coast of the Asian continent) and the fact that cloves came that way to Sri Lanka for sale. By the time of the Eastern Roman ruler Justinian I (r. 527–565 AD), the Byzantines purchased Chinese silk from Sogdian intermediaries. They also smuggled silkworms out of China with the help of Nestorian monks, who claimed that the land of Serindia was located north of India and produced the finest silk.Luttwak (2009), p. 168. By smuggling silkworms and producing silk of their own, the Byzantines could bypass the Chinese silk trade dominated by their chief rivals, the Sasanian Empire.

From Turkic peoples of Central Asia during the Northern Wei (386–535 AD) period, the Eastern Romans acquired yet another name for China: Taugast (Old Turkic: Tabghach). Theophylact Simocatta, a historian during the reign of Heraclius (r. 610–641 AD), wrote that Taugast (or Taugas) was a great eastern empire colonised by Turkic people, with a capital city northeast of India that he called Khubdan (from the Turkic word Khumdan used for the Sui and Tang capital Chang'an), where idolatry was practised but the people were wise and lived by just laws.Yule (1915), pp. 29–31; footnote #3 on p. 31. He depicted the Chinese empire as being divided by a great river (the Yangzi) that served as the boundary between two rival nations at war; during the reign of Byzantine Emperor Maurice (582–602 AD) the northerners wearing "black coats" conquered the "red coats" of the south (black being a distinctive colour worn by the people of Shaanxi, location of the Sui capital Sui Chang'an, according to the 16th-century Persian traveller Hajji Mahomed, or Chaggi Memet).Yule (1915), p. 30; footnote #2 on p. 30. This account may correspond to the conquest of the Chen dynasty and reunification of China by Emperor Wen of Sui (r. 581–604 AD). Simocatta names their ruler as Taisson, which he claimed meant Son of God, either correlating to the Chinese Tianzi (Son of Heaven) or even the name of the contemporary ruler Emperor Taizong of Tang (r. 626–649 AD).Yule (1915), p 29; footnote #4 on p. 29. Later medieval Europeans in China wrote of it as two separate countries, with Cathay in the north and Mangi in the south, during the period when the Yuan dynasty led by Mongol ruler Kublai Khan (r. 1260–1294 AD) conquered the Southern Song dynasty.Haw (2006), pp. 170–171.Wittfogel & Feng (1946), p. 2.Yule (1915), p. 1.

Chinese geography

Geographical information about the easternmost territories of the Roman Empire is provided in traditional Chinese historiography, although very little was known about the core Roman territories. The Shiji by Sima Qian ( 145–86 BC) gives descriptions of countries in Central Asia and West Asia. These accounts became significantly more nuanced in the Book of Han, co-authored by the Ban siblings, whereof the second Ban Chao led military exploits into Central Asia before returning to China in 102 AD. The westernmost territories of Asia as described in the Book of the Later Han compiled by Fan Ye (398–445 AD) formed the basis for almost all later accounts of Daqin.For the assertion that the first Chinese mention of Daqin belongs to the Book of the Later Han, see: Wilkinson (2000), p. 730. These accounts seem to be restricted to descriptions of the Levant, particularly Syria.