A basket of Buddhist scriptures had arrived in Tibet from India in the fifth century during the reign of Thothori Nyantsen, the twenty-eighth king of Tibet according to the Tibetan legendary tradition.
Written in Sanskrit, they are not translated into Tibetan until the reign of king Songtsän Gampo.
While there is doubt about the level of Songtsän Gampo's interest in Buddhism, it is known that he married a Chinese Tang Dynasty Buddhist princess, Wencheng, who had come to Tibet with a statue of Shakyamuni Buddha.
It is clear from Tibetan sources however that some of his successors became ardent Buddhists.
The records show that Chinese Buddhists are actively involved in missionary activity in Tibet, they do not have the same level of imperial support as Indian Buddhists, with tantric lineages from Bihar and Bengal.
Songtsän Gampo according to a Tibetan legendary tradition also married a Nepalese Buddhist princess, Bhrikuti.
He will already be regarded by the second half of the eighth century as an embodiment of the Bodhisattva Avalokiteśvara.
Emperor Taizong of Tang had meanwhile sent the general Li Jing against Tuyuhun in late 634 and, in a major campaign, had overpowered Tuyuhun's Busabo Khan Murong Fuyun, who was killed in flight.
Tang thereafter appointed Murong Fuyun's son Murong Shun as Tuyuhun's khan and, after Murong Shun was assassinated late in 635, supported Murong Shun's son Murong Nuohebo as khan.
Feng Dexia appeared to have gotten to Tibet around the same time.
By this time, Songtsän Gampo is aware that, in the past, the khans of the Eastern Turkic Khaganate and Tuyuhun had arranged marriages of state with China and therefore sends an emissary to accompany Feng back to Tang with further tribute to request to marry a Tang princess.
Emperor Taizong had received the emissary with elaborate courtesy; he reciprocates four years later by dispatching a group of high officials to visit the Tibetan monarch.
When the Tibetan emissary returns to Tibet, he informs Songtsän Gampo, falsely according to Tibetan historical sources, that Taizong was disposed to approve a dynastic marriage but changed his mind after hearing the Tibetans slandered by the Tuyuhun.
It was said that Murong Nuohebo had visited Tang and was interfering, leading to Taizong's refusal.
Songtsän Gampo, believing the report, attacks Tuyuhun in late 637 and early 638, capturing some of them and forcing the rest to flee north of Qinghai Lake.
