SOCIAL SCIENTIST indicated above, the British soon began a war with Sikkim and the ceded territory was annexed by them which was ratified by the Treaty of Tunlong (1861). The third phase was marked by the outbreak of the Anglo-Bhutan war which ended in the Treaty of Sinchulia (1865) and led to the British annexation of the hill tract which was situated to the east of the Tista river, the west of the Ne-chu and De-chu rivers, and the south of Sikkim. In other words, the total territory of the present three hill subdivisions of Darjeeling district - i.e., Darjeeling, Kurseong and Kalimpong sub-divisions - historically belonged to Sikkim and Bhutan before their annexation to British India. However, there is no recorded historical evidence that these three hill sub-divisions were ever a part of Nepal. As mentioned above, only the Terai portion of the Siliguri sub-division (and not the hills in the other sub-divisions) was for a short time conquered by Nepal from Sikkim, but was soon returned to Sikkim in 1816, long before the district of Darjeeling took shape. The thrust of the English East India Company towards Darjeeling and the adjacent region was motivated by several factors. One of the major reasons emanated from the geo-political importance of Darjeeling as being a part of Sikkim with which the British commercial compulsions were also closely associated. Throughout the 19th century the British interest in the overland trade with Tibet and Central Asia and the concomitant urgency for safeguarding the northern border of India against China and Tibet turned out to be the guiding parameters in the British policy towards the kingdoms of Sikkim, Bhutan and Nepal. Sikkim was of special interest to the English rulers because of its strategic position. The borders of the kingdom of Sikkim touched China, Nepal, Bhutan and India. The small kingdom commanded the historic Kalimpong-Lhasa trade route which was the shortest one from India to the heart of Tibet. Two main ranges of the Himalayas - the Singalila range and the Chola range - enclosed Sikkim on the north of Darjeeling district and it was bounded on either side by Nepal and Bhutan. In the wake of the Gorkha conquest of Nepal led by Prithvinarayan Shah, the British rulers were obliged, since the closing decades of the 18th century, to shift a major volume of their trade with Tibet and Central Asia through Sikkim to the Chumbi Valley and thence to Lhasa and Central Asia. However, after the successful conclusion of Anglo-Nepal war through the Treaty of Segauli (1816), the English rulers were able to contain the territorial ambition of the Gorkha kings of Nepal who hence forward began to maintain a friendly relation with British India. With the annexation