Complex sentence: Mo-ho-yen had been disseminating Dharma in the Tun-huang locale, but lost an important philosophical debate on the nature of emptiness from the Indian master Kamalashila, and the king declared Kamalashila's philosophy should form the basis for Tibetan Buddhism.
Split into simpler sentences: Mo-ho-yen had been disseminating Dharma in the Tun-huang locale at the time. Moheyan lost the important philosophical debate on the nature of emptiness to the Indian master Kamalashila, and the king declared that Kamalashila's philosophy should form the basis for Tibetan Buddhism.