It was legal in the Byzantine Empire but it was transformed significantly from the 4th century onward as slavery came to play a diminished role in the economy.
[5] Slavery was never abolished in the Byzantine Empire, but gradually diminished during the centuries; reaching its maximum in the 10th-century, it then transitioned to serfdom in the countryside, and remained only as a minor urban phenomena by the 13th-century.
The slave trade adjusted to this, and the result was that pagans, who could be sold to both Christians and Muslims, came to be highly valued.
Danielis of Patras, a wealthy widow in the 9th century, gave a gift of 3,000 slaves to Emperor Basil I.
A medieval Arab historian estimates that 200,000 women and children were taken as slaves after the Byzantine reconquest of Crete from the Muslims.
[8] After the 10th century the major source of slaves were often Slavs and Bulgars,[12] which resulted from campaigns in the Balkans and lands north of the Black Sea.
The old Greek word "δοῦλος" (doulos) obtained a synonym in "σκλάβος" (sklavos),[14] perhaps derived from the same root as "Slav".
[15] Ahmad ibn Rustah, a 10th-century Persian traveler, remembers it this way:The Magyar country (Etelköz) is rich in wood and water.
They make piratical raids on the Slavs and follow the coast [of the Black Sea] with their captives to a port in Byzantine territory named Karkh.
[17][18] The so-called saqaliba, which was the term for white slaves in the Islamic Middle East (often provided by the Vikings), is not likely to stand for exclusively Slavic ethnicity in practice, since many victims of the Vikings' saqaliba slave trade was in fact other ethnicities such as Baltics, Lithuanians, and Finno-Ugric people.
[19] The Vikings also captured slaves in raids from all of Western Europe, from the British Isles to France and Spain.
People taken captive during the Viking raids in Western Europe, could be sold to Moorish Spain via the Dublin slave trade[20] or transported to Hedeby or Brännö and from there via the Volga trade route to Russia, where slaves and furs were sold to Muslim merchants in exchange for Arab silver dirham and silk, which have been found in Birka, Wolin, and Dublin;[21] initially this trade route between Europe and the Abbasid Caliphate passed via the Khazar Kaghanate,[22] but from the early 10th century onward it went via Volga Bulgaria and from there by caravan to Khwarazm, to the Samanid slave market in Central Asia and finally via Iran to the Abbasid Caliphate.
[23] Archbishop Rimbert of Bremen (d. 888) reported that he witnessed a "large throng of captured Christians being hauled away" in the Viking port of Hedeby in Denmark, one of whom was a woman who sang psalms to identify herself as a Christian nun, and who the bishop was able to free by exchanging his horse for her freedom.
The pagan Lithuanians, Latvians, Estonians, Livonians, and Latgallians raided each other, Ingria and Novgorod during the 12th- and 13th-centuries, and sold war captives south to the Black Sea slave trade.
[27] The island of Saaremaa was a base for the Baltic pirates, who were noted for selling women captives to the slave trade.
Also, the legal system made it advantageous for masters to place them in certain economic positions, such as foremen of shops.
The scholar Kathryn Ringrose says they "represented a distinct gender category, one that was defined by dress, assumed sexual behavior, work, physical appearance, quality of voice, and for some eunuchs, personal affect.
[34] Initially, a major use for slave labor were the large agricultural estates, where the landowers could own thousands of slaves; but this form of slavery were gradually replaced by serfdom during the centuries, which eventually made slavery in the Byzantine Empire to become a minor urban phenomena.