Slavery begins to appear in explicit and extensive reference in surviving historical records following the raids of Mahmud of Ghazni in the 11th century. Many chroniclers claim that his campaign of 1024 in which he sacked Ajmer, Nehrwala, Kathiawar, and Somnath was particularly successful in garnering more than 100,000 Hindu slaves for the Muslim general.
...
The minority status of Muslim rulers perhaps led to periodic attempts at coercive measures as a punitive and preemptive terror tactic to keep the majority subject communities under control, with the Delhi Sultanate and its replacement under Babur trying to effectively turn areas under their close proximity and direct military control in India into Dar-ul-Islam (where Islamic law and custom was common). Some texts also contain passages that support claims for automatic annulment of marriages of captive women, or their immediate redistribution as "righthand possessions" among the winning army. In this sense, Islam could be cited by the ruling elite and their retainers itself as justification and recommendations for enslavement of non-Muslims under their military subjugation. Slave markets existed in most major towns in India, especially those where Muslims formed a large minority or majority such as Delhi.
One writer notes that "Mohammad Ghori needed a large number of slaves for his campaigns in India and for administration in and outside India. During his time, Lahore and Delhi rose to be prime centres of slave trade and the Sultan used to purchase slaves in bulk."
....
Probably the greatest factors contributing to the increased supply of Indian slaves for export to markets in Central Asia in this period were the military conquests and tax revenue policies of the Muslim rulers in the subcontinent. The early Arab invaders of Sindh in the 700's, the armies of the Umayyad commander Muhammad bin Qasim, are reported to have enslaved tens of thousands of Indian prisoners, including both soldiers and civilians. According to the Persian historian Firishta, after the Ghaznavid capture of Thanesar (c. 1014), "the army of Islam brought to Ghazna about 200,000 captives, and much wealth, so that the capital appeared like an Indian city, no soldier of the camp being without wealth, or without many slaves", and that, subsequently Sultan Ibrahim’s raid into the Multan area of northwestern India yielded 100,000 captives.
