The word was often used to refer specifically to Slavic slaves, but it could also refer more broadly to various other ethnicities of Eastern Europe traded by the Arab traders, as well as all European slaves in some Muslim regions like Spain and Portugal including those abducted from raids on Christian kingdoms of Spain and Portugal.
There were several major routes for the trading of Slavic slaves into the Arab world: through Central Asia (Mongols, Tatars, Khazars, etc.)
Theophanes mentions that the Umayyad caliph Mu'awiya I settled a whole army of 5,000 Slavic mercenaries in Syria who had defected from the Byzantine side in the 660s.
[6] After the battle of Sebastopolis in 692, Neboulos, the archon of the Slavic corps in the Byzantine army, and 30,000 of his men were settled by the Umayyads in the region of Syria.
In Iberia, Morocco, Damascus and Sicily, their military role may be compared with that of mamluks in the Ottoman Empire.
The Volga trade route was established by the Varangians (Vikings) who settled in Northwestern Russia in the early 9th century.
The Rus used this route to trade with Muslim countries on the southern shores of the Caspian Sea, sometimes penetrating as far as Baghdad.
Most Slavic slaves were imported to the Muslim world through the border between Christian and Islamic kingdoms where castration centres were also located instead of the direct route.
With the conversion of Eastern Europe, the trade declined and there isn't much textual information on Saqaliba after 11th century.
[14] Due to the Byzantine Empire and Venice blocking Arab merchants from European ports, they later started importing in slave from the Caucasus and the Caspian Sea.
[20] People taken captive during the Viking raids across Europe could be sold to Moorish Spain via the Dublin slave trade[21] or transported to Hedeby or Brännö in Scandinavia and from there via the Volga trade route to present day Russia, where slaves and furs were sold to Muslim merchants in exchange for Arab silver dirham and silk, which have been found in Birka, Wollin and Dublin;[22] initially this trade route between Europe and the Abbasid Caliphate passed via the Khazar Kaghanate,[23] 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.
Until the 6th- and 7th-century, the Balkans belonged to the Byzantine Empire, but was split by invasions of the Avars, Slavic tribes and other peoples.
[29] In the 9th and 10th centuries, the Slavs in Eastern Europe were still adherents of the Slavic religion, making them Pagans to the Christians and infidels to the Muslims and considered as legitimate targets for enslavement by both.
The Pagan Slavic tribes of Central and Eastern Europe were targeted for slavery by several actors in the frequent military expeditions and raids alongside their lands.
Louis the Fair granted his permission to Jewish merchants to traffick slaves through his Kingdom provided they were non-baptized Pagans.
[37] In Moorish al-Andalus, European Saqaliba-slaves were considered as exotic display objects with their light hair, skin and eye colors.
[37] White European slaves were viewed as luxury goods in Al-Andalus, where they could be sold for as much as 1,000 dinars, a substantial price.
[30] The saqaliba slave trade from Prague to al-Andalus via France lost its religious legitimacy when the Pagan Slavs of the North started to gradually adopt Christianity from the late 10th century, which made them of bounds for Christian Bohemia to enslave and sell to Muslim al-Andalus.
[40] During the warfare between Rome and the Byzantine Empire in Southern Italy in the 9th century the Saracens made Southern Italy a supply source for a slave trade to Maghreb by the mid-9th century; the Western Emperor Louis II complained in a letter to the Byzantine Emperor that the Byzantines in Naples guided the Saracens in their raids toward South Italy and aided them in their slave trade with Italians to North Africa, an accusation noted also by the Lombard Chronicler Erchempert.
[42] The Saracens captured the Baleares in 903, and made slave raids also from this base toward the coasts of the Christian Mediterranean and Sicily.