The middle ages, not sure there were many East European slaves in pre-Islamic Arabia. Also plenty of them were “imported” into the Byzantine empire and Italy. After the Vikings Venice and Genoa mostly controlled the slave trade in the Eastern Mediterranean, the Black Sea and also the Balkans (Venice had a massive slave market).

Italians and Spaniards were sold as slaves in North Africa and were still perfectly able to colonize.

Those were overwhelmingly women.