Mohammed Ghori had the Hindu temples of Ajmer demolished and ordered the construction of mosques and Quran schools on their ruins…He plundered Kanauj… - Muhammad bin Bakhtiyar Khalji

In short, when Muhammad Bakhtiyar became aware of the nature of the country, and saw that his men were tired and exhausted, and that many had been slain and disabled in the first day’s march, he consulted with his nobles, and they resolved that it was advisable to retreat, that in the following year they might return to the country in a state of greater preparation. On their way back there was not left on all the road a single blade of grass or a bit of wood. All had been set on fire and burnt. The inhabitants of the valleys and passes had all removed far away from the road, and for the space of fifteen days not a sir of food nor a blade of grass or fodder was to be found, and they were compelled to kill and eat their horses.

In the lofty nine-storied temple at Buddha Gaya, which was formerly called the Mahagandhola (Gandhalaya), the images of the past Buddhas were enshrined. The nine-storied temple called Ratandadhi of Dharamganja (university) of Nalanda was the repository of the sacred books of the Mahayana and Hinayana Buddhist Schools. The temple of Odantapuriihara, which is said to have been loftier than either of the two (Buddha Gaya and Nalanda) contained a vast collection of Buddhist and Bratiminical works, which, after the manner of the great Alexandrian Library, was burnt under the orders of Mohamed Ben Sam, general of Bakhtyar Kihilji, in 1212. A.D.

There could be little doubt, however, that the person who was directly responsible for the destruction of the Odantapuri and Vikramasila monasteries was Ikhtiyar-ud-din Muhammad bin Bakhtiyar Khalji...