India’s post-independence Nehruvian scholars, in order to impose western theological ideology of secularism within the arena of Indian history, were focused on glorifying foreign Muslim invaders and whitewashing their atrocities on Indic kings, subjects, and their places of worship. In that zeal, they conveniently overlooked one important chapter:

Hindu slavery under Muslim dominion. While it is true that slavery was not introduced in India by the foreign Muslim invaders and had existed in India even in the BCE era, historically the system was institutionalized and turned into a hugely profitable business during Muslim rule, which focused on the expansion of slavery for both commercial and political purposes. 

Prior to this, slavery in ancient India was humanist in nature and slaves were not seen as commodities for making profit through sale, a major reason why foreigners like Megasthenes, aware of the fate of slaves in western nations, failed to see any slaves in India and declared that all Indians were free (Indica of Megasthenes, cited in Om Prakash, “Religion and society in Ancient India,” 1985, p. 140).

While the western world right from ancient times was well acquainted with slavery, it was Islam that started the practice of slave trade, taking it to gargantuan proportions, making it run for profit like any other commercial activity.  Ibn Ishaq, he had set a precedent by selling few captured Jewish women and children of Medina in exchange for horses and weapons in Egypt. The Quran also expressly permits Muslims to acquire slaves through conquest. 

Slavery and empire-formation tied in particularly well with iqta and it is within this context of Islamic expansion that elite slavery was later commonly found. It became the predominant system in North India in the thirteenth century and retained considerable importance in the fourteenth century. Slavery was still vigorous in fifteenth-century Bengal, while after that date it shifted to the Deccan where it persisted until the seventeenth century. It remained present to a minor extent in the Mughal provinces throughout the seventeenth century and had a notable revival under the Afghans in North India again in the eighteenth century.

— Al Hind, André Wink (Al-Hind: the Making of the Indo-Islamic World, vol. 1, pgs. 14-15)