It is no news that Genghis Khan was tolerant of all religions. Neither is it news that Hitler was a vegetarian. Let us now look at two of the numerous principalities that emerged when mightier Mongol empires had disintegrated and were ruled by Genghis’ real or pretended descendants: the khanates of Kazan (1438–1556) and Crimea. We will find less tolerance in those Muslim states, although their rulers cared much less about religion than Ottoman sultans. What we find, though, is that those khanates were major suppliers of Slavic slaves to Ottomans — slaves that Kazan and Crimean horsemen captured in frequent raids into Russian and Ukrainian lands.
I’ve been going through Essays on the History of the Kazan Khanate by Mikhail G. Khudyakov (1894–1936). The book was first published in the 1920s, when the Bolsheviks were big on minority empowerment and “anti-imperialism”. Thus Khudyakov can’t be accused of a pro-Moscow bias. Regarding Russian captives in the Kazan Khanate, he writes:
On August 17  representatives of the Russian government suggested that the Khan begin freeing the captives. The Khan sent out police officers, ordered to gather all the captives on his premises and announced they were free. That day, 2700 people were freed. According to the Russian government’s rolls… 60,000 slaves were to be set free in the Kazan Khanate.
Khudyakov estimates the population of Kazan at 30,000 to 40,000 at its peak.
The Crimeans were keen on avenging the demise of Kazan (Moscow took over the Kazan Khanate in 1556); they succeeded in 1572. Khudyakov notes:
According to contemporary accounts, in Moscow and its surroundings alone, up to 800,000 people died; 150,000 were taken away as captives [read slaves]. The total population loss had to be above one million — and Ivan Vasilyevich’s [Grozny’s] domain had hardly counted 10 million subjects. The devastated areas were ancient and the most cultured; it was not for nothing that Muscovites, for long afterwards, counted years beginning with the Tatar destruction, as in the 19th century time would be counted from “the year 1812” [Napoleon’s capture of Moscow].