Slavery and slave-trading was common in Europe throughout the Middle Ages. It is documented in a great variety of sources, many of them not directly pertaining to the subject of slavery. Broadly speaking, two large categories of slaves may be identified: 1) chattel slaves, who were maintained and ruled by a master, and bought and sold; 2) unfree peasants, who, because they managed their own farms, some historians do not consider slaves. However, unfree peasants lacked rights and freedoms, and were just as subject to abuse from their owners as chattel slaves. By the twelfth century, unfree peasants had become serfs, and it is thought that slavery then diminished in Northern Europe. In the rest of medieval Europe, however, chattel slavery continued. Indeed, in the early Middle Ages slave trading was Europe’s largest commercial enterprise, and slaves were moved from one end of the continent to the other, especially Slavs, who gave us our modern word slave. This trade was initially directed towards the southern and eastern Mediterranean, which had greater wealth and market demand than most of Europe. By the twelfth century, the idea had arisen that Christians should not enslave Christians, and for the rest of the Middle Ages most slaves in Medieval Europe were Muslims or ‘pagans’; the cities of the Mediterranean north coast, such as Venice and Genoa, made big business of selling pagans in the both the Islamic and Christian worlds. The majority of these slaves were women, often sold for sexual exploitation. They were increasingly from ethnic minorities originating outside of Europe, which led, by the late medieval period, to the concept of the racial identity of slaves.