Justifying Slavery

The changing shape of the slave trade in the medieval Mediterranean.

The Christian reconquest of Spain significantly altered the Iberian slave market. In Aragon, conquered Muslims were promised judicial autonomy as part of the surrender treaties signed with King Jaime I of Aragon. Cases that were supposed to be adjudicated by Islamic law, however, were instead arbitrated in Christian courts and Muslims in Christian Aragon were subject to the rule of the king’s deputy, the General Bailiff. He had authority over the Muslim population, who were considered to ‘belong to the king’. The General Bailiff could seize, try and imprison Muslims for criminal activity and frequently did so in cases of sexual relations between Muslims and Christians. In Islamic law, criminal convictions for adultery could be punished with public flogging or stoning; but under Christian courts, punishment was enslavement to the Crown. The Crown was spurred, too, by financial interest; it received a lucrative portion of the sale price for each slave. As a result, the number of Muslim slaves sold in Christian markets increased significantly.  

The Church sanctified the slave trade by arguing that religious differences justified slavery. Christian law accepted the institution of slavery and permitted Christians to keep non-Christian slaves. Written about the Christian Crusades, Gratian’s Decretum, a collection of canon law produced in Bologna in 1140, explicitly defended the enslavement of Muslims; Gratian’s view became instrumental in later medieval justifications of Muslim slavery. 

According to James Boswell in The Royal Treasure (1977), the slave trade in Muslims was energised following the first outbreak of the Black Death in 1347. Corsairs from Valencia, Barcelona, Majorca, Venice and Genoa acquired slaves along the coasts of the Muslim kingdoms of Granada and those of North Africa, selling them in Christian markets. These raids reached their peak during the late 14th century, following the Black Death’s initial outbreak.  

As a result of the catastrophic death rate, medieval Iberia was left with a depleted workforce. One option for employers was to hire immigrants to fill the labour shortage left by the Plague, but because of the limited population numbers and the high demand for labour, workers had begun to command high wages and better conditions. Employees became increasingly unaffordable to many Iberians and they took to buying slaves instead to cut expenses, leading directly to a dramatic increase in the slave trade. An ordinance from the city of Barcelona in the late 1300s clarifies that this had become common practice following the Plague:

When the said city [of Barcelona] is mistreated by … labourers … and [they] harm citizens, … and profit from the city … by asking for immoderate wages, … as they have for the last forty years [since the Black Death], … they force [the citizens of Barcelona] to buy slaves

Demand for slaves in Aragon was so high in the late 14th century that the supply started to diversify and Orthodox Christian slaves, including Circassians, Russians, Slavs, Bulgarians, Albanians and Greeks, all began to appear in Iberia from areas around the Eastern Mediterranean. When relations between the eastern Christian churches and the western Roman Catholic Church deteriorated in 1054, Eastern Orthodox Christians were considered legitimate targets of the western European slave traders. Animosity between the eastern Orthodox Churches and western Christendom revived in the second half of the 14th century, following the Black Death, and eastern Orthodox Christians were again subject to enslavement as heretics. 

When the trade in Eastern Orthodox slaves was at its highest, in 1375, the historian Francisco Javier Marzal Palacios has estimated that they represented over 50 per cent of the total Valencian slave population. By the late 1300s, efforts by Church officials and royals had reduced the trade of eastern Orthodox Christians on the premise that Christians should not enslave their co-religionists. King Juan I of Aragon gave eastern Orthodox Christian slaves in his kingdom the right to claim their freedom in court in 1380. It was only with the 1453 Ottoman capture of Constantinople, however, that slave traffic from the eastern Mediterranean into Iberia really tapered off.

The European population finally resumed sustained growth in the 1450s. With an increase in population, the labour supply grew, employers were able to recruit paid labourers at lower salaries and slave labour became less important, greatly reducing the flow of slaves into Iberia.  

By 1450, European merchants had developed new trading networks in and across the Atlantic Ocean and Spain’s attention shifted towards western Africa and the Atlantic, changing the direction of the slave trade and the make-up of the slave population. European traders began to emphasise racial distinctions to gain support for the enslavement of African populations with whom they came into contact. Race, rather than religion, became the new marker of difference that made enslavement legitimate. 

Johan MacKechnie is a PhD candidate in History at Queen’s University, Canada, researching religious communities in the late-medieval Mediterranean.