How Silkworms Saved the Byzantine Economy

The Economic Revival of the Roman World Was Due to Worms

Detail from Byzantine silk placed in the tomb of Holy Roman Emperor Charlemagne in Aachen (Musée National du Moyen Age, Cluny, Paris). 

The Byzantine Empire had its ups and downs throughout its millennium of existence. At numerous points, it faced a significant crisis but then craftily found a way to surmount it. These methods were so clever and tricky that we still use the word "byzantine" to describe them. In the Sixth Century, right before just such a grave crisis descended upon the empire, the lowly silkworm enabled the Byzantines to dodge an economic sinkhole and continue to finance the military on which the Byzantine state's survival depended.

Silk was very well known to Romans from the days of the Roman republic onward. Shown is a Roman fresco from Pompeii of a Meanade in a sheer silk dress (Naples National Archaeological Museum).

The Importance of Silk in the Roman World

The Roman Empire and its successor state, the Byzantine Empire, had numerous customs and traditions that reflected their place in the ancient world. For instance, purple dye was a sign of royalty. One of these traditions was the use of silk for certain specific purposes. These included the use of a 3.4 meter-wide silk coronation mantle for Byzantine emperors. Silk was considered so important that it became a constant trading commodity that was a prime source of state revenue. Purple silk was so exclusive that only the Emperor, his family, and his retinue could wear it.

Pliny the Elder was a bit confused but also impressed by silk. He bemoaned the trade imbalance resulting from the purchase of this expensive luxury for women.

Silk, despite its source in far-off places, had been around since roughly the time of Alexander the Great ca. 300 BC. The Romans for many centuries had no idea how it was made and thought it derived from some kind of plant. Pliny the Elder (23/24 AD - 79), for instance, sniffed in The Natural History VI, 54 that silk was a bit fabulous for his tastes: 

The Seres (Chinese), are famous for the woolen substance obtained from their forests; after a soaking in water they comb off the white down of the leaves… So manifold is the labour employed, and so distant is the region of the globe drawn upon, to enable the Roman maiden to flaunt transparent clothing in public.

At roughly the same time as Pliny, Seneca the Younger (3 BC-65 AD) also decried silk as befitting only the lowest class of women (Excerpta Controversiae 2.7):

I can see clothes of silk, if materials that do not hide the body, nor even one's decency, can be called clothes ... Wretched flocks of maids labour so that the adulteress may be visible through her thin dress, so that her husband has no more acquaintance than any outsider or foreigner with his wife's body.

Pretty much everybody else, though, loved and respected silk's feel and appearance, however. Silk was important not just because it was rare and expensive, but because it was the absolute height of fashion in sophisticated circles. It was a symbol of political authority, required for church events, and an obligatory fashion accessory throughout the aristocracy. In fact, silk use was codified in sumptuary laws. As with all luxury goods, it was prized by people who could pay quite generously for it. Ordinary workers couldn't wear silk (laws prevented that), but the lords and ladies at the villas where they worked might.

Byzantium controlled the two main routes over which silk could be obtained, the northern overland route and the southern shipping route through Egypt.

If anything, silk was more important in the Byzantine Empire than it had been in the Roman Empire (and here is why we divide the two empires by name, because they were not identical). Whereas men were forbidden by law from wearing silk in the Roman Empire, Byzantine men increasingly preferred silk to the classic Roman woolen toga. Byzantines, in fact, often wore unisex (ungendered) outfits, and they often included at the very least silk trim.

Byzantine emperors (Basilei) controlled the trade in silk. They reserved the right to grant or deny the right to import or export silk to other states. Given Byzantium's geographical control of the trade routes from the East where the finest silk was produced (some silk was made in Syria beginning at least as long ago as the fifth-century using local worms, but this silk was considered inferior). These permits were highly prized and a key source of revenue for the Byzantine state.

The Roman outpost in the Farasan Islands, which are located at the lower right of the globe where the red line crosses the Red Sea, was the furthest from Rome in the entire Empire. This outpost was there specifically to protect the trade with India for silk and other valuable commodities (Google Earth).

The importance of silk was hardly a secret. It was a common import into the key Byzantine trade ports on the Red Sea and the Black Sea. The sea trade with India was so important that the furthest Roman outpost in the entire Empire was along this route, on the Farasan Islands in the Red Sea. However, the trade routes were always tenuous, depending on what foreign powers controlled the territories over or near which the silk had to travel from the production centers in China and India. The vulnerability of the sea routes is shown by the need for the Romans to station a garrison so far away along this route. These routes could be closed in an instant when hostilities commenced, though they always reopened eventually because the trade was too lucrative to eliminate. It did not take a genius to figure out that it would be extremely beneficial to the Byzantine treasure if the middlemen could be cut out entirely and production of silk moved within the Byzantine Empire itself.

A trade caravan on the Silk Road (© North Wind Picture Archives).

The roadblock to the Byzantine production of silk was that the people in the major Asian silk centers also prized the silk trade. It was a great source of revenue for them and they had no interest in giving up their monopoly. The only potential customer for silk west of Persia was Byzantium, so keeping the secret out of their hands was critical. Within Byzantium, the only allowed to buy silk legally was one official, the comes commerciorum, a low-ranking kommerkiaros or customs agent who was based in a border town. He had utter control over the entire silk trade and could set trading prices or shut it down completely on his own initiative or as directed by Constantinople. Byzantine power did not extend far enough into the Far East or subcontinent of India to ever contemplate seizing the silkworms that were the foundation of the entire industry. Silkworms also were known to be extremely fragile and unlikely to survive the long, hot, and dry journey overland across deserts either in Asia or Egypt.

Illustration of Byzantine embassy, most likely from Emperor Constans II, to Tang Taizong in 643 AD.

The Byzantines, however, did have regular contacts with the areas which manufactured silk aside from simple merchants. For instance, Roman political emissaries appeared at the royal court in China from time to time at least as early as 166 AD. The Chinese "Book of the Later Han" records these Romans arriving by sea via Vietnam, which was the obvious travel choice for non-traders. While of historical interest, these diplomatic initiatives accomplished virtually nothing. One other source of contact, however, had more concrete results. These were missionaries who traveled widely, were inconspicuous, and who had a habit of making friends in high and low places.

Justinian is best remembered for his military victories, which overall were magnificent but fleeting. His underappreciated introduction of the silkworm, though, may have saved the Empire.

Justinian's Good Fortune

Two of these missionaries, believed to be monks of the Nestorian Church (a splinter Christian religion), learned about the silk industry at its source and returned to Constantinople in 551 AD. They had a business proposition for Emperor Justinian. Once granted an audience with him, the two monks explained to the bemused emperor how silk was actually made and the process of cultivating silkworms. While we don't know all the details of this arrangement (basically the only source is court official Procopius, who did not go into a lot of detail), the monks promised to steal silkworms and bring them back alive for the Emperor to do with as he pleased. While Justinian was usually preoccupied with his constant wars of conquest, he also was very interested in the silk trade because he knew that the trade benefited the Empire's enemies to the East, Sassanid Persia.

Justinian, in fact, had begun a war with Persia that had destroyed the private silk factories at Berytus and Tyre. The scarcity of silk had forced him to institute price controls for silk, which in turn had dried up the supply from Persia in line with the usual forces of supply and demand. This had produced a shortage of silk in Byzantium, and Justinian had been forced to practice an early form of socialism and nationalize failing silk factories. So, the silk industry was something that Justinian thought about a lot. Probably not believing his good fortune, Justinian quickly agreed to the monks' terms - whatever they were - and sent them on their way.

A typical view of the ancient city of Panjakent, a city in Sogdiana that was prosperous until the Arab (Umayyad) conquest of Transoxiana ca. 722 AD. 

Details about this critically important incident are scarce and have only one account as a primary source, that of Procopius. The common narrative is that the monks had learned about the silk industry during a visit to China in 551. However, this is supposition, and it is just as likely that they learned about the industry while preaching Christianity for the Church of the East in India. In other words, it is highly likely that the "monks" (if that is what they actually were, for why would monks engage in commerce with an emperor?) never visited China in their lives. The sea route to India was much, much easier than any route to China, and it had been used for hundreds of years. In any event, if they did travel to China to get the worms, it would have involved a hazardous route along the Black Sea, through the Transcaucasus, and over the Caspian Sea before a long ride past Sogdiana in modern Uzbekistan. Reflecting the importance of this route, a Turko-Sogdian diplomatic party visited Byzantine Emperor Justin II in Constantinople in 568 AD to confirm their trade route from China.

As an aside, it would have been much easier for the Monks to simply take a merchant ship from Berenice on the Red Sea to an Indian port, or, in the unlikely event that they actually visited China, even all the way to Vietnam as earlier delegations had done. The monks would have been very familiar with the route to India and it could have been done in a few weeks or months, depending on their choice of transportation and sense of urgency. But, whatever route the monks took, they accomplished their goal within about two years.

Two monks give Emperor Justinian the silkworms they have smuggled out of China ("The Introduction of the Silkworms" (Vermis Serious) ca. 1595 AD).

The most famous part of the monks' expedition was the way they transported the silkworms, which became legendary. The monks wisely did not take mature silkworms but instead smuggled out silkworm eggs or very young larvae, which is the only form in which they could have survived the journey. These eggs and larvae the monks hid in their bamboo walking sticks. One can imagine the border guards searching the monks as they stood before them, tapping their canes that were full of the most precious cargo of the age.

The monks also arranged separately for the transport of the Mulberry bushes on which the silkworms depended. Within two years, the monks were back in Constantinople and delivered their precious cargo to the aging Justinian. They also brought Chinese slaves who were educated in the ways of sericulture (the production of silk).

"The Introduction of the Silkworms" (Vermis Serious) engraving by Karel van Mallery, ca. 1595. This depicts seven women spreading the eggs on cloth (left) and then wrapping them with eggs (right).

Justinian acted quickly. He (and his successors) established royal silk factories in Constantinople, Beirut, Antioch, Tyre, Thebes, Corinth, and Syria. It took decades for the silk industry to really take hold because of the way in which silkworms make silk, but eventually, these factories broke the Chinese, Indian, and Persian silk monopoly.

A depiction of the Chinese princess who supposedly smuggled silk cocoons out of China in her marriage crown (Dandan-Oilik, 6th Century AD, British Museum collection).

A Note About Procopius

It is always important to be skeptical of ancient sources, especially when there is only one source for important information such as the origins of the Byzantine silk industry. They all have agendas, biases, and a desire to "tell a good story." So, taking everything they say at face value is dangerous.

A good example is Anna Comnenus, the sole source for Emperor Alexius Comnenus (1081-1118), who just so happened to be her father. Everything Alexius did was just magnificent and almost god-like, apparently. Obviously, Anna loved her father.

Procopius, on the other hand, at least in his official writings (leaving aside his "Secret History"), was basically a propagandist for Justinian and his policies. It is doubtful that the tale he told was entirely accurate, and that may not be his fault because he was relying on what he was told by people who may have had an interest in embellishing the facts.

Here is what Procopius actually wrote about the silkworm incident in "On the Wars":

About the same time there came from India certain monks; and when they had satisfied Justinian Augustus that the Romans no longer should buy silk from the Persians, they promised the emperor in an interview that they would provide the materials for making silk so that never should the Romans seek business of this kind from their enemy the Persians, or from any other people whatsoever. They said that they were formerly in Serinda, which they call the region frequented by the people of the Indies, and there they learned perfectly the art of making silk.

Moreover, to the emperor who plied them with many questions as to whether he might have the secret, the monks replied that certain worms were manufacturers of silk, nature itself forcing them to keep always at work; the worms could certainly not be brought here alive, but they could be grown easily and without difficulty; the eggs of single hatchings are innumerable; as soon as they are laid men cover them with dung and keep them warm for as long as it is necessary so that they produce insects. When they had announced these tidings, led on by liberal promises to the emperor to prove the fact, they returned to India. When they had brought the eggs to Byzantium, the method having been learned, as I have said, they changed them by metamorphosis into worms which feed on the leaves of mulberry. Thus began the art of making silk from that time on in the Roman Empire

Just to be clear, there are other theories about how Byzantium received its silkworms that have nothing to do with two monks making a deal with Justinian. One story is that a Chinese princess in 440 AD loved silk so much that she smuggled some silkworms with her when she married a foreign prince (the Prince of Khotan), and that is how they got to Sogdiana in the first place. Another ascribes the theft from China to Japanese spies. Byzantine historian Theophanes, writing at the beginning of the ninth century, tells basically the same tale as Procopius, but instead of two monks going to China, it is a Persian who smuggles the silkworm eggs out of Central Asia in a walking stick. 

In summary, Procopius tells a great story that sounds a little too neat and, despite its threadbare narrative, includes some unlikely events. But Procopius's version has become the accepted one.

Byzantine silk depicting an imperial lion hunt, ca. 650 AD.

The Economic Impact of Silk Production

Procopius makes it sound as if the instant the worms hit the dirt within the Byzantine Empire, silk was plentiful. This wasn't the case. It took decades to establish the industry, a distribution network, and develop the types of patterns of fine garments that befit royalty. However, the Byzantines succeeded in becoming among the preeminent silk manufacturers of the Middle Ages. They developed leaving patterns that still exist, such as the tapestry, tabby, damask, twill, and lampas weaves. Byzantine silks were renowned for their vivid colors, gold thread, and elaborate designs. If paintings by the likes of Rembrandt and Michelangelo became the height of medieval European culture, silks were the epitome of Byzantine art. 

Thus, it wasn't just about silkworms, but also about artistry and fashion. It's a little like the auto industry in 20th Century America, which wasn't just about the cars themselves but about building roads and fuel and spare parts and tires and many other entire sub-industries. The silk industry created a revival in late-Roman manufacturing just when it was needed the most.

Byzantine silk featuring imperial eagles, ca. 10th Century.

And this economic revival came just in the nick of time. By 646 AD., less than a hundred years later, the economic situation of the Empire had drastically changed for the worse. The sea route to India and points further east was closed from 618-629 when the Sassanid Empire occupied Egypt, and then eliminated for good when the Arab tribe of 'Ak, led by Amr ibn al-As, conquered Egypt. This was a hard military blow to the Byzantine Empire, but an even more devastating economic one. Egypt always provided about 40% of the Imperial Roman Empire budget, and it must have added a much larger fraction of the revenues for the much smaller Byzantine Empire. Losing Egypt blew a major hole in the budget that could have been fatal.

In addition, Egypt for centuries had been the food basket of the empire. Losing the food was bad, but Egypt also was the trade gateway to India and northern Africa via Egyptian ports. There was no way to detour around the Red Sea to Abyssinia or southern India. That trade provided huge custom revenues The new economy founded around the silkworm replaced a large fraction of that. It proved invaluable to the Byzantine Empire, filling the royal coffers for centuries until the silk factories were finally overrun following the Latin conquest of Constantinople in 1204.

The silk trade was extremely lucrative for Constantinople and supported the lavish spending by many emperors. While Byzantine silk production was at its height, the Byzantine gold nomisma coin served as the world's reserve currency, used for mercantile transactions outside the Empire as well as within it, supplanting the Persian silver coin. This wealth served as the key foundation of Byzantine foreign policy, which often involved buying off enemies. It is only after the Byzantine silk trade collapsed and the Byzantine coin lost its preeminence that the empire entered its terminal phase.

Byzantine Nilotic silk (Abegg-Stiftung Textile Museum, Riggisberg, Switzerland).

2021