A form of forced conversion became institutionalized during the Ottoman Empire in the practice of devşirme, a human levy in which Christian boys were seized and collected from their families (usually in the Balkans), enslaved, forcefully converted to Islam, and then trained as elite military unit within the Ottoman army or for high-ranking service to the sultan. From the mid to late 14th, through early 18th centuries, the devşirme–janissary system enslaved an estimated 500,000 to one million non-Muslim adolescent males. These boys would attain a great education and high social standing after their training and conversion.