to the Doklam plateau and descending to the Amo Chu valley through the Sinche La pass. It continues along the river to the hamlet of Asam on what was then regarded as the border of Tibet, and proceeds to the town of Rinchengang, which was a border trade mart. According to scholar Jigme Yeshe Lama, such paths were used for ages by traders, nomads and pilgrims. India's Sikkim state lies to the west of the Dongkya range, the western shoulder of the Doklam plateau and the 'southwest spur' issuing from Mount Gipmochi. This spur is cut by the Dichu river (also called Jaldhaka) which originates below the Jelep La pass and enters Bhutan. The 'southeast spur', called Zompelri ridge, separates Bhutan's Haa District (to the north) from the Samtse (to the south). Bhutan's claimed border runs along the northern ridge of the Doklam plateau until Sinchela and then moves down to the valley to the Amo Chu river. China's claim of the border includes the entire Doklam area within the Chumbi Valley, ending at the Zompelri ridge on the south and the confluence of the Torsa Nala with Amo Chu on the east. Strategic significance Scholar Susan Walcott counts China's Chumbi Valley, to the north of Doklam, and India's Siliguri Corridor, to the south of Doklam, among "strategic mountain chokepoints critical in global power competition". John Garver has called the Chumbi Valley "the single most strategically important piece of real estate in the entire Himalayan region". The Chumbi Valley intervenes between Sikkim and Bhutan south of the high Himalayas, pointing towards India's Siliguri Corridor like a "dagger". The latter is a narrow 24 kilometer-wide corridor between Nepal and Bangladesh in India's West Bengal state, which connects the central parts of India with the northeastern states including the contested state of Arunachal Pradesh. Often referred to as the "chicken's neck", the Siliguri Corridor represents a strategic vulnerability for India. It is also of key strategic significance to Bhutan, containing the main supply routes into the country. Historically, both Siliguri and Chumbi Valley were part of a highway of trade between India and Tibet. In the 19th century, the British Indian government sought to open up the route to British trade, leading to their suzerainty over Sikkim with its strategic Nathu La and Jelep La passes into the Chumbi Valley. Following the Anglo-Chinese treaty of 1890 and Younghusband expedition, the British established