He unified several Tibetan kingdoms,[2] conquered lands adjacent to Tibet, and moved the capital to the Red Fort in Lhasa.

[3] His mother, the queen, is identified as Driza Thökar (Tibetan: འབྲི་བཟའ་ཐོད་དཀར་, Wylie: 'bri bza' thod dkar, ZYPY: Zhisa Tögar).

[11] Songtsen sponsored the building of two temples to house the images of Buddha brought by his Nepalese and Chinese wives, however he showed little interest in propagating Buddhism otherwise, and was buried according to pre-Buddhist protocols and rituals when he died.

[14] Songtsen Gampo's heir, Gungsong Gungtsen, died before his father, so his younger son Mangsong Mangtsen inherited the throne.

[15][16] Tibetan Empire-era documents found at Dunhuang say that Songsten Gampo also had a sister Sad-mar-kar (or Sa-tha-ma-kar) and a younger brother bTzan-srong who was betrayed and died in a fire, c. 641.

According to one partially damaged scroll from Dunhuang, there was hostility between Sa-tha-ma-kar and bTzan-srong, who was then forced to settle in gNyal (southeast of the Yarlung River and across the 5,090 metres (16,700 ft) Yartö Tra Pass, which borders on modern Bhutan, and Arunachal Pradesh in India).

[20][21][22] According to Tibetan tradition, Songtsen Gampo was enthroned while still a minor as the thirty-third king of the Yarlung dynasty after his father was poisoned circa 618.

Songsten Gampo then retired for four years to learn the written language, after which he translated twenty-one tantric texts on Avalokiteshvara, and the Mani Kumbum.

"[35] Traditional accounts say that, during the reign of Songtsen Gampo, examples of handicrafts and astrological systems were imported from China and the Western Xia; the dharma and the art of writing came from India; material wealth and treasures from the Nepalis and the lands of the Mongols, while model laws and administration were imported from the Uyghurs of the Second Turkic Khaganate to the North.

The inscription on the Skar cung Pillar (erected by Ralpacan, who ruled c. 800–815) reports that during Songtsen Gampo's reign, "shrines of the Three Jewels were established by building the temple of Ra-sa [Lhasa] and so on.

The king's minister, Nyang Mangpoje Shangnang, with the aid of troops from Zhangzhung, defeated the Sumpa in northeastern Tibet circa 627 (Tibetan Annals [OTA] l. 2).

[42] Tang dynasty chronicles describe this as a tribute mission, but it brought an ultimatum demanding a marriage alliance, not subservient rituals.

[44] The Old Book of Tang do seems to place these events clearly in the reign of Songtsen Gampo, for they say that in 634, Yangtong (Zhangzhung) and various Qiang peoples "altogether submitted to him."

"[26][60][61] Sometime later, but still within the Zhenguan period (627–650 CE), the Tibetans sent an envoy to present day Nepal, where the king received him "joyfully", and, later, when a Tibetan mission was attacked in present-day India by then minister of emperor Harshavardhan who had usurped the throne after emperor Harshavardhan's death around 647 CE,[62] the Licchavi king came to their aid.

The Chinese Princess Wencheng, niece of the Emperor Taizong of Tang, left China in 640 to marry Songtsen Gampo, arriving the next year.

According to Chinese sources, "As the princess disliked their custom of painting their faces red, Lungstan (Songtsen Gampo) ordered his people to put a stop to the practice, and it was no longer done.

He also sent the children of his chiefs and rich men to request admittance into the national school to be taught the classics, and invited learned scholars from China to compose his official reports to the emperor.

"[65] However, according to Tibetologist John Powers, such accounts of Tibet embracing Chinese culture through Wencheng are not corroborated by Tibetan histories.

Following the visit by the famous Chinese pilgrim monk Xuanzang to the court of Harsha, the king ruling Magadha, Harsha sent a mission to China which, in turn, responded by sending an embassy consisting of Li Yibiao and Wang Xuance, who probably travelled through Tibet and whose journey is commemorated in inscriptions at Rajagrha - modern Rajgir – and Bodhgaya.