It is inherent in the unity of past and present that Marxist historiography must continuously turn to fresh aspects to explore and re-explore and fre… - Irfan Habib

The pressure of new circumstances led initially to large-scale slave-trading and the emergence of slave labour during the thirteenth and fourteenth centuries. The numbers of slaves in the Sultans' establishments were very high (50,000 under Alauddin Khilji, and 180,000 under Firuz Tughluq). Barani judges the level of prices by referring to slave prices, and the presence of slaves was almost all-pervasive.

"The evidence for such enslavement is there for all to see. So economically important was it that the success of military campaigns was often judged by the number of captives (burdas) obtained for enslavement. Qutbuddin Aibak's campaign in Gujarat in 1195 netted him 20,000 slaves, seven years later a campaign against Kalinjar yielded 50,000. In 1253 Balban obtained countless 'horses and slaves' from an expedition in Kalinjar. In the instructions that Alauddin Khalji is said to have issued to Malik Kafur before his campaigns in the Deccan it is assumed that 'horses and slaves' would form a large part of the booty. As the Sultanate began to be consolidated, the suppression of mawas or rebellious villages within its limits yielded a continuously rich harvest of slaves. Balban's successful expedition in the Doab made slaves cheap in the capital. How people of the village could be made slaves for nonpayment of revenue is described in the 14th century sources; and women so enslaved are mentioned in different contexts in two others".

Without undue modesty, we can say we know more about India’s past than Marx did.