The Mongols were so terrified by the military strength of Alauddin Khalji that after 1308 a.d. they did not attack at all and the idea of establishing their rule over India vanished from their hearts. The following factors were chiefly responsible for the defeat of the Mongols and the successes of Alauddin Khalji:
1. Alauddin Khalji was a fortunate ruler. Every time something happened in his favour and it tilted the scales of victory towards him. The retreat of Targhi was a stroke of luck, otherwise Alauddin was going to surrender very soon.
2. Alauddin was a competent commander. He consolidated the north-west frontier in such a way as it became difficult for the Mongols to cross it. His powerful, trained and well-equipped soldiers not only defeated them but also terrorized them, hence Alauddin achieved victories over the Mongols.
3. Alauddin was himself an able soldier, great commander and an efficient warrior. He attained success against the Mongols by his qualities referred to above. Qutlugh Khwaja was no match to the leadersaip and fighting capacity of the Sultan.
4. Alauddin did not face the Mongol invaders alone. He sought the confidence and support of his public, nobles and provincial governors in order -to defeat them.
5. In the beginning, the Mongols had a goal to conquer the entire world and tried their best to attain this objective but by now several weaknesses handicapped them. They involved themselves in the intricate problems of Central Asia and lost their way. Mutual conflicts among the Mongols further weakened them and they could not fight against Muslims as one compact unit.
6. Constant decline in military power was another vital reason of the defeat of the Mongols against the Muslim army. Their war strategy was also defective. They used to bring with them their women and children at the time of invasion. It put hindrances in their way and crippled their speed which was the root cause of their failure.
7. The Mongols had acquired enough of kingdoms and wealth. They could feel content with their achievements. It affected their capabilities otherwise and hurled them towards decline.
8. They were very powerful in the beginning but with the passage of time they began to lack in bravery, tolerance and endurance. Owing to these weaknesses they soon got frustrated and fled the battlefield.
9. They did not like to settle down at one place for a long time and were not competent in the art of besieging a fort. They failed to achieve success against Alauddin due to their tendency of excitement.
10. Death of Dava Khan was also a weighty reason for their failures. His aim was to conquer Delhi. In spite of his failure, he invaded Delhi again and again and sent various expeditions. His followers did not act according to his ideals and were entangled in internal conflicts, so they had no time to invade India due to their domestic problems and feuds.