Between 1717 and 1734, during the reign of the fourth king, a series of wars were fought with the Bhutanese which resulted in the loss of much territory in the southern foothills including Kalim pong, then a very important bazaar town on the trade route leading from Tibet to India. More territory was lost after 1780 following the Gurkha invasion from Nepal though the invaders were eventually checked by a Chinese army with Bhutanese and Lepcha assistance. Unable to advance into Tibet, the Gurkhas turned south and came into conflict with the British East India Company.

A series of wars were fought between the two parties ending in the treaty of 1817 whereby the borders of Nepal were delineated and the Gurkhas ceded to the British all the Sikkimese territory they had taken. A substantial part of this territory was returned to the Raja of Sikkim in return for control by the British of all disputes between Sikkim and its neighbors. The country thus became a buffer state between Nepal, Tibet and Bhutan.

In 1835, the British, seeking a hill station as a rest and recreation centre lot its troops and officials, persuaded and -pressured the Raja into ceding the Darjeeling area in return for an annual stipend. The Tibetans objected to this transfer of territory as they continued to regard Sikkim as a vassal state and filarjeeling's rapid growth as a trade Sentre began to make a considerable Impact on the fortunes of the leading lamas and merchant of Sikkim. Tensions rose and in 1849 a high ranking British official and a botanist who were explor ing the Lachen region with the pennis-sion both of the Sikkimes Raja and British government, were arrested. Following threats of intervantion, the two prisoners were unconditionally released a month later but the British annexed the whole of the area between the present Sikkimese border thc Indian plains and withdrew the Raja's stipend (the latter was eventually restored to his son).

Further British interference in (the affairs of this area led to the declaration of a protectorate over Sikkim in 1961 and the delineation of its border. The Tibetans, however, continued In regard all these actions as illegal and in 1886 invaded Sikkim to reassert their authority. They were thrown, back by the British and a military expedition sent to Lhasa in 1888 as a punitive pleasure, The powers of the Sikkim Raja were further reduced and high handed treat ment by British officials prompted him to flee to Lhasa in 1892 though he was eventually persuaded to return Being keen to developed the area, the British encouraged immigration from Nepal, as they had done In Darjeeling, and a considerable amount of land was brought under rice and cardamom cultivation. As a result of this influx of labour, which wan still going on right up until the 1960s, the Nepalese constitute some 75% of the population of Sikkim. The subject became a heated topic of discussion in the late 60s and the Kaja was constrained to prohibit further immigration. Further steps were taken to placate those of non-Nepalese origin in the form of new laws regarding the rights of citizenship but these inflamed the opposition political parties. The Raja's American-born wife was also active in stirring up a resentment against the Nepalese and matters eventually reached a head with demonstrations in Gangtok and the flight of the Raja to India. Though India had inherited the treties with Sikkim from the British at independence they were in no mood to be seen propping up the regime of an autocratic Raja in Sikkim while doing their best to sweep away the last traces of princely rule in India itself. Their response to this instability in a very sensitive border region with China was to pension off the Raja and annex the country. Though there was now governed by its own democratic congress with representatives in the central government in New Delhi.