Whites were enslaved by the early Ottoman Turks.
In the 14 century Murad 1 build an army of slaves, converted them to Islam and trained them as the sultans personal servicemen, in fact the sultan enslaved children and trained them to be war slaves called the Janissaries, most of these Janissaries were made up of Greeks, Albanians, Georgians, Southern Russians, Serbs and Ukrainians, were originated to be Christians and were forced to convert to Islam some theories indicate that a few originated from European migrantion.
The lucrative Barbary slave trade, Barbary pirates would acqcuire rounding up slaves and selling them to the Ottoman and the Moors, Barbary pirates would raid on coastal towns around Italy to the Netherlands and would travel as far north to Iceland and the Mediterranean
The Barbary wars: In 1801 Thomas Jefferson ordered the Naval fleet along with the Kingdom on Sicily and Sweden to fight against the Ottoman Empire and the Sultanate of Morocco, sources say that over a million of European slaves were saved by the hands of the Ottoman regime.
tl.dr: Slavery is a social problem, not a racial issue, Blacks that bitch and moan about race relations cannot evolve from their culture.