treaties concluded by the khans with neighbouring rulers. For a long time, until the early 18th century, the khanate maintained a massive slave trade with the Ottoman Empire and the Middle East. Caffa was one of the best known and significant trading ports and slave markets. Crimean Tatar raiders enslaved between 1 and 2 million slaves from Russia and Poland–Lithuania over the period 1500–1700. Caffa (city on Crimean peninsula) was one of the best known and significant trading ports and slave markets. In 1769, a last major Tatar raid resulted in the capture of 20,000 Russian and Ruthenian slaves. Barbary slave trade Slave markets flourished on the Barbary Coast of North Africa, in what is modern-day Morocco, Algeria, Tunisia, and western Libya, between the 15th and middle of the 19th century. These markets prospered while the states were nominally under Ottoman suzerainty, though, in reality, they were mostly autonomous. The North African slave markets traded in European slaves which were acquired by Barbary pirates in slave raids on ships and by raids on coastal towns from Italy to Spain, Portugal, France, England, the Netherlands, and as far afield as the Turkish Abductions in Iceland. Men, women, and children were captured to such a devastating extent that vast numbers of sea coast towns were abandoned. According to Robert Davis, between 1 million and 1.25 million Europeans were captured by Barbary pirates and sold as slaves in North Africa and Ottoman Empire between the 15th and 19th centuries. However, to extrapolate his numbers, Davis assumes the number of European slaves captured by Barbary pirates was constant for a 250-year period, stating: Davis's numbers have been challenged by other historians, such as David Earle, who cautions that the true picture of European slaves is clouded by the fact the corsairs also seized non-Christian whites from eastern Europe and black people from west Africa. A second book by Davis, Holy War and Human Bondage: Tales of Christian–Muslim Slavery in the Early-Modern Mediterranean, widened its focus to related slavery. It is also worth noting that there were wide fluctuations from year to year, particularly in the 18th and 19th centuries, and also given the fact that, prior to the 1840s, there are no consistent records. Middle East expert John Wright cautions that modern estimates are based on back-calculations from human observation. Such observations, across the late 1500s and early 1600s observers, account for around 35,000