Tibetan Empire reached its zenith under Songtsen Gampo's descendant Tri Song Detsuen in 755 AD who expanded Tibet politically and economically and promoted Buddhism to bring the nation together. However, about a century after him, the empire collapsed and Tibet entered its traditional "dark age." The Mongols conquered Tibet in 1244 but let the local Buddhist leaders manage the administrative affairs and Tibet gradually eased into a Theocracy as the Dalai Lama was acknowledged as the Spiritual Head.

In 1950, China, looking for a buffer zone between itself and India, invaded Tibet.