[1] The region consisting of present-day Sikkim, Chumbi Valley and western Bhutan was largely a frontier territory since early seventeenth century.
[7] Around the same time, the Bhutanese state was getting unified under Ngawang Namgyal and would enter into a protracted conflict with an expansionist Tibet — the first war was fought in late 1650s, which the Tibetans lost comprehensively.
[14] In the meanwhile, Bhutan's religio-military assault kept on the rise with chronicles recording a dispatch of forces to nearby Dagana in 1650, to subdue recalcitrant monpas — this might have affected Damsang as well.
[15] Despite these hurdles, including what he notes to be an increased presence of Bhutanese monks, Gyaltshan managed to exert significant command in the local population.
[11][13] By the time he returned c. 1663, more Lamas from Bhutan had encroached on his territories and a local Lepcha chieftain, Gaeebo Achyok, had assumed control.
[11][f][g] In 1668 Gaeboo Achyok sought assistance from the 5th Dalai Lama, and had an audience with him at Lhasa; that, Bhutanese expansions had triggered conflicts with the Tibetans on multiple fronts, he expected a favorable response.
[21][10] Early in 1675, Achyok informed the Tibetans that the Bhutanese were secretly preparing for an all-out offensive against him before the expiry of the peace treaty.
[22][19] While routine border incursions were commonplace,[10] this was an unprecedented development and the Dalai Lama ordered a preemptive attack, which was carried out, burning a frontier outpost at Tendung.
[10][24] Rituals were held in Punakha for the vitalization of Bhutan's forces and by the third month of 1676, the fort was taken back; Gaeboo Achyok was captured and executed while his territories were annexed.
[24] War preparations were initiated, and months later, Tibet would mount the largest ever invasion of Bhutan with eleven columns of army aiming to besiege them from all sides.