Ghori decided to invade Gujarat which was Chalukya king Mulraja-II's domain. It is unfortunate for India that Prithviraj and Mulraja-II were not on good terms with each other. Thus, the former remained an amused spectator while the latter faced the enemy. In the battle that followed Ghori was defeated. Had both the Indian kings combined and faced the enemy, they would have inflicted a crushing defeat on the invader who probably would not have again gathered courage to even dream about conquering India. 

Mohammed Ghori proposed a peace treaty to Prithviraj, while he was invading the other parts of the country but the proud Rajput refused to enter into any alliance with him. After the withdrawal of the invader, Prithviraj found good opportunity to expand. Though he followed an aggressive policy towards his neighbours, yet he could not get much territorial gains. He developed enmity with Jaya Chandra, the powerful king of Kannauj because of two reasons - one due to the desire of both to dominate over North India  and the other due to his romance with Sanyogita, Jaya Chandra's daughter. 

War with the Muslim invader was becoming inevitable because Mohammed Ghori was determined to invade and conquer India whereas Prithviraj, being on the gate of India, was determined to face the enemy and not to allow him to proceed further. In 1191 AD Ghori proceeded towards India and captured Bhatinda. Prithviraj too advanced towards Bhatinda to check the enemy's advance. Both the armies faced each other at Tarain. In the first battle of Tarain Mohammed Ghori was defeated. It was with great difficulty that a Khilji noble could save his life and took him away from there. Prithviraj won a victory but did not chase him and inflict a crushing defeat on him. He allowed the enemy to leave India and did not take full advantage of the situation which had arisen out of this victory.

Mohammed Ghori, after the defeat at Tarain was on the look out for an opportunity when he could strike back and take revenge. In 1192 AD he again invaded India with a huge army of 1,20, 000 armed men. Both the armies faced each other again at Tarain. Prithviraj had the support of his feudal chiefs but these were only small princes. No powerful ruler extended his support to him even at this critical juncture. Thus, for all practical purposes he had to face the enemy single handed.

Prithviraj realised that the enemy was in an advantageous position and proposed a peace treaty to the invader. He offered him Bhatinda and East Punjab. The invader found it a good pretext to prepare for war. He kept Prithviraj engaged in peace talks and finding an opportunity suddenly attacked him and inflicted a crushing defeat on him. Prithviraj was caught and killed. This was the turning point in the history of India. Thus, Delhi and gradually the rest of India fell into the hands of Muslims.    

Reasons for Prithviraj's defeat:

• Prithviraj's expansionist policy resulted in enmity with other Rajput and neighbouring states who did not side with him when the enemy was on their head and knocking on the doors of India. Had all the Indian kings forgotten their enmity, combined together and given a united fight to the invader, victory would have touched their feet and the history of our country would have been altogether different. 
• Being at the doorsteps of North India and in the constant danger of Muslim invasion, Prithviraj should have developed good intelligence system, which he failed to do.
• Prithviraj could not foresee that the enemy could take advantage of the time when he was negotiating for peace talks with him. As a shrewd ruler he should have sent his intelligence to find out how far the enemy was serious about his peace negotiations.
• At the time of both first and second battles of Tarain, Prithviraj allowed the enemy to come up to Bhatinda. It is after the fall and capture of Bhatinda that he proceeded to check the advance of the enemy. It was decidedly a wrong policy. He should have checked the enemy as soon as it was known that the invader was proceeding towards India. It was obviously more difficult to root out an enemy once he was on the soil of India. Instead of being offensive he remained defensive and acted only when attacked upon.
• After his victory in the first Battle of Tarain, Mohammed had been defeated and was being removed as an injured person. It was an appropriate time when he should have vigorously followed and tried to kill him. He should have created havoc for demoralised and defeated army of the enemy and taught it a lesson not to see towards India again. But Prithviraj allowed the opportunity to miss.

Modern India has a lot to learn from the mistakes of Prithviraj Chauhan. We Indians continue to repeat the same mistakes - right from Prithviraj Chauhan to Kargil. In spite of having suffered so much, we seem not to have learnt any lessons from our history. Lessons to be Learnt:

• Internal conflicts and differences must be forgotten when faced by external threat. Whatever are the differences, while fighting the foreign forces we must be united. United we stand, divided we fall.
• We must always be vigilant and develop a good intelligence system so that we are aware of the enemy's movements in advance.
• We must not get carried away by enemy's sweet friendly talks. While the enemy is acting friendly, we must keep our eyes and ears open so as to know his real motive and not let him fool us.
• We must not wait to retaliate till the enemy has attacked and harmed us. As soon as we see signs of evil designs, we must attack and crush the enemy. Offence is the best defense.
• We must never show mercy to the enemy or pardon him. When victorious, we must take full advantage of the situation. The enemy must be punished at the first opportunity we get to do so. If he is pardoned, he will recover and come back with greater force.