Ralpachen

Tritsuk Detsen (Tibetan: ཁྲི་གཙུག་ལྡེ་བཙན, Wylie: khri gtsug lde btshan), better known by his nickname Ralpachen (Tibetan: རལ་པ་ཅན, Wylie: ral pa chen; c. 802–838), was the 40th King (Tsenpo) of Tibet from c. 815 to 838. He reigned after the death of his father, Sadnalegs, and grew the empire to its largest extent. He was murdered by his younger brother Langdarma in 838. Ralpachen is one of the "Three Dharma Kings of Tibet", and referred to as "son of God" in the ancient Tibetan chronicle Testament of Ba.

Ralpachen was the second eldest of five brothers. The eldest, Prince Tsangma, took Tibetan Buddhist vows with the Nyingma school. The third, U Dumtsen known as Langdarma, is referred to in the sources as "unfit to reign". The younger two brothers both died young.

Ralpachen is considered a very important king in the history of Tibet and Tibetan Buddhism, as one of the three Dharma Kings (chosgyal) of the Yarlung Dynasty, which include Songtsen Gampo the 33rd king, Trisong Detsen the 38th king, and Ralpachen. All three kings respectively contributed in bringing Mahayana Buddhism to Tibet, in revealing the Vajrayana through Guru Padmasambhava, and in supporting the growth of Buddhism, the building of monasteries, and the flourishing of Buddhism with imperial patronage.

The Tibetan Empire during the reign of Ralpachen grew to its largest extent, and the military battles with the Tang Empire led to the 821–823 Tibet–Tang treaty. Three stelae were inscribed with the terms, and one of each was built in Lhasa at the Jokhang Monastery, in Chang'an, and at the agreed border.

The death of Ralpachen in 838 ended the imperial patronage of Tibetan Buddhism, which had begun about eighty years earlier around 755 with Padmasambhava, Shantirakshita and Trisong Detsen. Afterwards, Langdarma, Ralpachen's brother and successor, proceeded to nearly destroy Buddhism in Tibet, together with the 13 Buddhist monasteries, and their ordained monastics, which were built during the reign of Trisong Detsen.