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.
Levi notes that these figures cannot be entirely dismissed as exaggerations since they appear to be supported by the reports of contemporary observers. In the early 11th century Tarikh al-Yamini, the Arab historian Al-Utbi recorded that in 1001 the armies of Mahmud of Ghazni conquered Peshawar and Waihand, "in the midst of the land of Hindustan", and captured some 100,000 youths. Later, following his twelfth expedition into India in 1018-19, Mahmud is reported to have returned to with such a large number of slaves that their value was reduced to only two to ten dirhams each. This unusually low price made, according to Al-Utbi, "merchants came from distant cities to purchase them, so that the countries of (Central Asia), Iraq and Khurasan were swelled with them, and the fair and the dark, the rich and the poor, mingled in one common slavery". Elliot and Dowson refers to "five hundred thousand slaves, beautiful men and women". Later, during the Delhi Sultanate period (1206–1555), references to the abundant availability of low-priced Indian slaves abound. Levi attributes this primarily to the vast human resources of India, compared to its neighbours to the north and west (Mughal Indian population being approximately 12 to 20 times that of Turan and Iran at the end of 16th century). Many of these Indian slaves were reserved for use in the subcontinent, but their availability in substantial numbers greatly contributed to their affordability, which likewise increased their demand in international markets.