What was the impact of the Mongol invasions on the Delhi Sultanate.

The Mongol invasions affected the Delhi Sultanate in the following ways: 

1. Both Alauddin Khalji and Muhammad Tughluq raised large standing armies against the Mongols. 

2. Alauddin constructed a new garrison town named Siri for his soldiers while Muhammad Tughluq emptied Dehli-i-Kunha of its residents and the soldiers garrisoned there. 

3. In order to feed the soldiers, large taxes were imposed on farmers. 

4. Alauddin chose to pay his soldiers salaries in cash rather than iqtas. His administrative measures were effective due to cheap prices and efficient supplies of goods in the market. Muhammad Tughluq created a token currency to pay his soldiers. His administrative  reign was a disaster and he disbanded his army. 

Alauddin was able to withstand the threat of Mongol invasions. Muhammad Tughluq's administrative measures failed, however, he atleast planned to attack the Mongols which was a first in the history of the Delhi Sultanate.