They did. It failed because North Western India is naturally fortified by the Hindu Kush mountains, but also has many defensive forts. Delhi Sultanate essentially annihilated the Mongol army.

>Farishta, a Persian scholar and historian of India writes:

>After the Mongols were defeated by the Sultan at the Ravi river, the Sultan ordered the Mongol prisoners to be transferred to Delhi, and to be slain, but the upper caste Hindoo soldiers of the Sultan refused, stating the the Mongols were a people of Dharma [likely a reference to Buddhism]. The Sultan thus ordered the lowest caste amongst the Hindoos, the Chāndālas, to serve as executioner of the captured 8,000 Mongols. The Chāndālas carried out the massacre without any hesitation, and a tower of skulls was erected to instill fear into Delhi's population that anyone who goes against the Sultan shall suffer the same fate as these Mongols.