Byzantine knowledge of China was filtered through Turkic and Indian intermediaries, and most Byzantine references to China are concerned with their role as a source of silk. The sixth-century Alexandrian merchant Cosmas Indicopleustes refers to China as Tzinitza, a name possibly of Persian or Sanskrit origin. In his Christian Topography, he briefly mentions that Tzinitza is responsible for the production of the silk found in Persia or India, and that Tzinitza was situated at the eastern edge of the known world:

The Indian philosophers, called the Brachmans, say that if you strech a cord from Tzinitza to pass through Persia, onward to the Roman dominions, the middle of the earth would be quite correctly traced, and they are perhaps right... Beyond Tzinitza there is neither navigation nor any land to inhabit.

However, there is one notable source that provides a remarkably extensive description of China, including a discussion of its political system. The seventh-century Byzantine historian Theophylact Simocatta includes several passages concerning Taugast in his History. The name Taugast may have originated from the Northern Wei (386–535), which was ruled by the Tuoba clan.

The regional commander of Taugast is called Taisan, which signifies "son of god" in the Greek tongue. The realm of Taugast is not troubled by discord, for lineage provides them with the selection of their leader. Statues are the cult of this nation, the laws are just, and their life is full of discretion. They have a custom, which resembles law, that males should never embellish themselves with gold adornment, even though they have become owners of a great abundance of silver and gold as a result of their large and advantageous trading.

In this passage, Theophylact correctly observes that succession to the throne in China was hereditary and that Son of Heaven was a title of the Chinese emperor (typically assumed to be a corruption of taizi or possibly the title of taishang). Theophylact then goes on to recount a war between two states in the region of Taugust (China).

A river divides this Taugast; now once long ago the river was interposed between two great nations who were mutually hostile; the dress of one was black, and of the other scarlet-hued. Then in our times, while Maurice was in possession of the Roman sceptres, the black-robed nation crossed the river and joined battle with those wearing the red clothing; next, having gained victory, it became master of the whole dominion.

G. F. Hudson identified this conflict as the reunification of northern and southern China by the Sui dynasty in 589. This would fit the timeline for Emperor Maurice, who reigned from 582 to 602. However, due to the references to "black robes" and "red robes", Peter Boodberg has argued that this passage corresponds to an earlier conflict in Chinese history: the conquest of Northern Qi by Northern Zhou in 577. This would imply that the river mentioned by Theophylact refers to the Yellow River rather than the Yangzi.

Boodberg cites several Chinese sources that associate Northern Qi with red uniforms and Northern Zhou with black uniforms during the period between 543 and 577. In the Sui Shu, colors are repeatedly use to symbolize dynasties, with yellow symbolizing the Sui, black symbolizing Zhou, and red symbolizing Qi. In one passage, a black serpent reportedly killed a red servant one year before the the destruction of Northern Qi in 577. Another passage mentions that a black dragon was said to have fallen from the sky in Northern Zhou that same year, alluding to the eventual defeat of Zhou by the Sui.

The next lines by Theophylact sound more fantastical:

This Taugast in fact, the barbarians say, was founded by the Macedonian Alexander when he enslaved the Bactrians and Sogdoane and burnt twelve myriads of barbarians. In this city the ruler's wives have carriages made of gold, each of which is drawn by one bullock lavishly decorated with gold and precious stones; and even the oxen's reins are gold-inlaid. And so the man who has assumed the dominion of Taugast used to pass the night with seven hundred women. The wives of the nobility of Taugast used silver carriages. There is a report that Alexander also founded another city a few miles away, which the barbarians name Chubdan; and that when the leader dies, he is mourned for ever by his wives, who have their heads shaved and who wear black clothing; and that it is the custom for these women never to leave the tomb. Chubdan is divided by two great rivers, whose banks nod, so to speak, with cypresses. The nation has many elephants.

Alexander's empire did not extend beyond the Indus region, much less reach China. Elephants are not native to Chubdan, identified as the Chinese city of Chang'an. The golden chariots seem to contradict Theophylact's earlier mention of a supposed ban on the decorative use of gold. There is also no evidence of prohibiting the adornment of gold in any Chinese sources. As to the origin of some of these claims, there is a tendency among Greek and later Arab sources to connect any far-off foreign land with the romanticized exploits of Alexander. The elephants in Chang'an could be referring to tributes brought from the south. There might even be a grain of truth in the shaven head claim. Boodberg speculates that this might be referencing imperial concubines who join a Buddhist monastery after the death of emperor.

Theophylact ends his description of China, which is really just a brief aside in his overall account of the diplomatic relations between the Byzantines and Turks, with familiar remarks regarding China as a source of silk.

They associate in trade with the Indians, and they say that these Indians who face the northern regions are actually born white. The worms, from which come the Seric threads, are possessed by the said nation in very great numbers and are in turn possessed of varied colour; the barbarians eagerly practise the husbandry of the said creatures.

Theophylact's portrayal of China is in some ways similar to the accounts of Rome in Chinese sources in that it is a mixture of fact and exaggerated claims acquired through intermediaries. It recalls a game of telephone. Sometimes the message gets garbled along the way, but there are instances where the information can be surprisingly accurate.

The translations come from:

• The Christian Topography of Cosmas, an Egyptian Monk. Trans. by McCrindle, J.W. London: Hakluyt Society, 1897.

• The History of Theophylact Simocatta. Trans. by Michael Whitby and Mary Whitby. Oxford: Clarendon Press, 1986.

And for further reading, see:

• Boodberg, Peter. "Marginalia to the Histories of the Northern Dynasties," Harvard Journal of Asian Studies 3 (1938): 223-53.

• Chen, Zhi-Qiang. "Narrative Materials about the Byzantines in Chinese Sources" from Byzantine Narrative: Papers in Honour of Roger Scott. Melbourne: Byzantina Australiensia, 2006.