Step onto the medieval Silk Road and you'll witness its intense wonders – and its hidden horror

But alongside the camels and caravans was another cargo: human beings.

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Enslaved people were transported and sold on the exact same routes that moved pepper and porcelain. They were bought, sold, gifted, inherited and transported across continents, from China to the Mediterranean. And for much of the medieval Afro-Eurasian world, their presence was so commonplace that it rarely provoked any moral questions – let alone outrage.

“On the medieval silk road, slavery was very, very prevalent,” says historian Claire Taylor, discussing the topic on an episode of the HistoryExtra podcast. “There are no societies that we know of that didn’t have slaves in one form or another.”

Medieval slavery everywhere, but rarely recorded

In the medieval world, slavery was woven into the economic, political and social life of societies: from the Islamic caliphates of the Middle East and Christian kingdoms of Europe, to the Mongol khanates of central Asia and imperial courts of China.

And yet, the enslaved people themselves are almost invisible in the historical record.

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“The historian Susan Whitfield has coined the phrase ‘the unknown slave’,” Taylor explains, “because we know so little about them. We only really know specific details about the more exceptional ones, but only in general terms about the less fortunate ones.”

Most enslaved people appear only fleetingly in records: in a merchant’s account book, a legal contract or an inventory of a deceased person’s property. A few – usually those who rose to prominence as soldiers or administrators, for example – emerge in more detail. But the majority remain nameless.

How medieval slavery differed from ancient and modern forms

Historians divide the story of slavery into broad phases. In the classical world of Greece, Rome and Carthage, slavery was an economic engine, providing the bulk of labour for agriculture, mining and household service. Thousands of years later, in the early modern era, the transatlantic slave trade bound slavery to racial ideology, with European powers trafficking millions of Africans to the Americas.

The medieval world operated differently.

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“In the medieval slave trade, we’re mainly talking about religious and political factors,” says Taylor.

Enslaved people were still considered property, deprived of autonomy, denied freedom of movement and vulnerable to horrific exploitation. But the lines of who could be enslaved were often drawn according to religion and political allegiance, rather than race.

How did these people become enslaved?

Capture and kidnap were some of the most common ways for someone to become enslaved along the Silk Road.

Steppe nomads raided settled communities; pirates targeted coastal towns; armies took captives in military campaigns. The Mongol conquests, for instance, generated vast numbers of enslaved people who were redistributed across Eurasia.

But equally, some slavery came from within a society. “Someone might be born a slave or become enslaved as a result of their criminality. There are also instances of ‘self-slavery’, where people might fall into debt and enter slavery as a result.”

Debt slavery was sometimes a survival strategy. In desperate conditions, a person might have sold themselves or their children into servitude to secure food or protection.

The morality of medieval slavery

To modern eyes, one of the most striking aspects of medieval slavery is the absence of widespread moral opposition to the institution itself.

“There are very few examples of people questioning the morality of this… there isn’t really a concept of shared humanity,” says Taylor.

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That’s not to say everyone was equally at risk, and there were rules for who would be deemed ‘enslavable’. Legal and religious systems often restricted who could be enslaved, creating what Taylor describes as “enslaving zones” and “no-slave zones”.

“There’s the idea that you shouldn’t enslave somebody of your own religion: that it’s okay for a Christian to enslave a Muslim, and for a Muslim to enslave a Christian. But it’s not okay within your own group.”

These restrictions were not based on the idea that outsiders were less than human, but rather that they were of the wrong faith, and therefore legitimate targets.

Slavery as political and military strategy

When it came to ideas of slavery, religion and politics often reinforced one another. In the Crusader States of the eastern Mediterranean, Christian leaders discouraged enslaving other Christians not because of humanitarian motives, but because it weakened their own population base.

“In the context of the Crusades, not enslaving other Christians and instead enslaving people of other faiths helps the war effort,” Taylor notes.

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For Muslim powers, the logic could be similar: protect the faithful, target outsiders. Enslaved captives could be put to work in agriculture, construction or domestic service, or traded for profit to distant markets.

Some regimes even incorporated slavery into military structures. In the Islamic world, elite slave-soldiers such as the Mamluks could rise to positions of great power – although this was a narrow path available to very few.

The moral world of medieval slavery

The medieval justifications for slavery can be jarring in their bluntness. Across the Afro-Eurasian world, it was a central pillar of social and economic life. The idea that there might be moral debates about slavery would have seemed alien to those who practised it.

In this context, morality was bound not by a belief in universal human freedom, but by political and pragmatic lines of faith, power and opportunity. On the roads of medieval Eurasia, where you fell according to those lines could have been the difference between liberty and a life of servitude.

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Claire Taylor was speaking to Emily Briffett on the HistoryExtra podcast. Listen to the full conversation.