Nepal's role in the expansion of Mahayana Buddhism beyond the Himalaya is very significant. Nepal became the center of Mahayana Buddhism after the Muslim invasion of Nalanda Mahavihara in the 1199 A.D., which she maintained almost for 300 years. During this period, Nepal had produced a large number of profound Buddhist scholars. Most of them were the teachers of eminent Tibetan Buddhists. Some of the Nepalese Gurus also has continued lineage in Tibet until now. During that time, every Tibetan had desire to go to Nepal for higher Buddhist learning. As a matter of fact, many Tibetans made arduous journey across the Himalaya to fulfill the dream. Tibetan studied various forms of tantra, precepts, logic, doctrine, Sutra, Sadhana, Doha, Charyagiti, meditation etc. under direct supervision of Nepalese teachers. Great Tibetan scholars such as Marpa, Rwa Lo, Chag Lo, Khon phu ba, Klog Lo, Gos Lo, and others were the product of Nepal's scholarly tradition. They have significant place in the history of Tibet. Nepalese scholars also frequently visited Tibet where they taught Buddhism in various monasteries. They also had major role in propagating tantra in Tibet. Tibetans firmly believe that it is not possible to attain enlightenment without practicing tantra. The contribution of Nepalese scholars was so profound that Tibet produced many eminent scholars who developed scholastic tradition in Tibet. But after 14th century, Nepal's scholarly tradition ceased to continue. Then after, Tibetans started to call them 'the dull'.