Slave-taking was a structural feature of Viking-age raiding rather than a by-product of it. Captives seized in Ireland, Britain, Frankia and the Slavic lands were held for ransom, kept as thralls in Scandinavia and the North Atlantic colonies, or sold on: Dublin functioned as one of Europe's principal slave markets, and the Rus river routes carried captives to Constantinople and the Islamic markets, where the silver that flows back into Scandinavian hoards is the trade's clearest surviving trace. Genetic and place-name evidence from Iceland indicates a substantial proportion of the founding female population came from Ireland and Britain. No total can be reconstructed: the annals record particular raids and not aggregates, and the trade left no registers. The practice declined in the eleventh and twelfth centuries with Christianisation and with church campaigns against the sale of Christians.
Scandinavian raiders and traders took captives from Ireland, Britain, Francia and the Slavic east and sold them through Dublin, Hedeby and the Volga route into Byzantium and the Islamic world
There is no register of captives and no single population acted upon. Estimates of the scale rest on chronicle notices of individual raids, on Irish and Frankish annals, on the Dublin and Hedeby slave markets, and on the volume of Islamic silver reaching Scandinavia, from which some historians infer tens of thousands of captives moved east across the ninth and tenth centuries. The populations concerned - Ireland at perhaps half a million, England at one to two million, the Slavic lands unenumerated - were never a single unit and changed greatly over 793-1100.
No usable figures. Raids killed, and mortality among captives in transit was presumably significant, but neither is recorded in any quantified form.
Captive-taking for thraldom and sale is documented in the Irish annals, Anglo-Saxon law and charter material, and the Arabic accounts of Rus traders, and is analysed in the Cambridge scholarship cited.
Ireland, Iceland, Russia, Bulgaria, Germany, Spain