Bhutan's early history is steeped in mythology and remains obscure. Some of the structures provide evidence that the region has been settled as early as 2000 BC. According to a legend it was ruled by a Cooch-Behar king, Sangaldip, around the 7th century BC, but not much is known prior to the introduction of Tibetan Buddhism in the 9th century, when turmoil in Tibet forced many monks to flee to Bhutan. In the 12th century, the Drukpa Kagyupa school was established and remains the dominant form of Buddhism in Bhutan today. The country's political history is intimately tied to its religious history and relations among the various monastic schools and monasteries.
View of Tashichoedzong, Thimphu. The 17th-century fortress-monastery on the northern edge of the city, has been the seat of Bhutan's government since 1952.
The Tsa Yig is any monastic constitution or code of moral discipline based on codified Tibetan Buddhist precepts. Every Tibetan monastery and convent had its own Tsa Yig, and the variation in Tsa Yig content shows a degree of autonomy and internal democracy.
Shabdrung Ngawang Namgyal instituted the Tsa Yig and the Cho-sid-nyi (dual system) in Bhutan
Penlop (governor) Ugyen Wangchuck consolidated power as Druk Gyalpo (hereditary monarch) and Druk Desi in Bhutan, and extensively revised the Tsa Yig