stylistic:tone, information:filtering, linguistic:translation
Tibetan Empire

The history of a unified Tibet begins with the rule of Songtsen Gampo (604–650 CE), who united parts of the Yarlung River Valley and founded the Tibetan Empire. He also brought in many reforms, and Tibetan power spread rapidly, creating a large and powerful empire. It is traditionally considered that his first wife was the Princess of Nepal, Bhrikuti, and that she played a great role in the establishment of Buddhism in Tibet. In 640, he married Princess Wencheng, the niece of the Chinese emperor Taizong of Tang China.

Under the next few Tibetan kings, Buddhism became established as the state religion and Tibetan power increased even further over large areas of Central Asia, while major inroads were made into Chinese territory, even reaching the Tang 's capital Chang'an (modern Xi'an) in late 763. However, the Tibetan occupation of Chang'an only lasted for fifteen days, after which they were defeated by Tang and its ally, the Turkic Uyghur Khaganate.

The Kingdom of Nanzhao (in Yunnan and neighbouring regions) remained under Tibetan control from 750 to 794, when they turned on their Tibetan overlords and helped the Chinese inflict a serious defeat on the Tibetans.

In 747, the hold of Tibet was loosened by the campaign of general Gao Xianzhi, who tried to re-open the direct communications between Central Asia and Kashmir. By 750, the Tibetans had lost almost all of their central Asian possessions to the Chinese. However, after Gao Xianzhi's defeat by the Arabs and Qarluqs at the Battle of Talas (751) and the subsequent civil war known as the An Lushan Rebellion (755), Chinese influence decreased rapidly and Tibetan influence resumed.

At its height in the 780s to 790s, the Tibetan Empire reached its highest glory when it ruled and controlled a territory stretching from modern-day Afghanistan, Bangladesh, Bhutan, Burma, China, India, Nepal, Pakistan, Kazakhstan, Kyrgyzstan, Tajikistan.

In 821/822 CE, Tibet and China signed a peace treaty. A bilingual account of this treaty, including details of the borders between the two countries, is inscribed on a stone pillar which stands outside the Jokhang temple in Lhasa. Tibet continued as a Central Asian empire until the mid-9th century, when a civil war over succession led to the collapse of imperial Tibet. The period that followed is known traditionally as the Era of Fragmentation, when political control over Tibet became divided between regional warlords and tribes with no dominant centralized authority. An Islamic invasion from Bengal took place in 1206.