Kingdom of Sikkim

The Kingdom of Sikkim (Classical Tibetan and འབྲས་ལྗོངས།, Drenjong), officially Dremoshong (Classical Tibetan and འབྲས་མོ་གཤོངས།) until the 1800s, was a hereditary monarchy in the Eastern Himalayas which existed from 1642 to 16 May 1975, when it was annexed  by India. It was ruled by Chogyals of the Namgyal dynasty.

Foundation of the Monarchy
According to legend, Khye Bumsa, a 14th-century prince from the Minyak House in Kham in eastern Tibet, received a divine revelation instructing him to travel south to seek his fortunes. A fifth-generation descendant of Khye Bumsa, Phuntsog Namgyal, became the founder of Sikkim's monarchy in 1642, when he was consecrated as the first Chogyal, or priest-king, of Sikkim by the three venerated lamas at Yuksom. Phuntsog Namgyal was succeeded in 1670 by his son, Tensung Namgyal, who moved the capital from Yuksom to Rabdentse (near modern Pelling). By the time of its foundation, Sikkim became a protectorate of Tibet (which at the time was part of The Khoshut Khanate until 1717, when became part of the Dzungar Khanate and later to The Qing Dynasty in 1720.)

Nepalese-Bhutanese domination
In the mid-18th century, Sikkim was invaded by both Nepal (then the Gorkha Kingdom) and Bhutan (then ruled by Gyalsey Tenzin Rabgye) and was under both the Gorkha and the Bhutanese rule for more than 40 years. Between 1775 and 1815, almost 180,000 ethnic Nepalis from Eastern and Central Nepal migrated to Sikkim. After the British colonisation of India, however, Sikkim allied itself with British India in order to fight Nepal, their common enemy at the time. The Nepalese then attacked Sikkim, overrunning most of the region including the Terai. This prompted the British East India Company to attack Nepal in 1814, resulting in the Anglo-Nepalese War. The Sugauli Treaty between Britain and Nepal and the Treaty of Titalia between Sikkim and British India resulted in territorial concessions by Nepal, which ceded Sikkim to British India.

British and Indian protectorate
Under the 1861 Treaty of Tumlong, Sikkim became a British protectorate, then an Indian protectorate in 1950.

Thutob Namgyal, the 9th Chogyal of Sikkim, looked to the Dalai Lama for spiritual leadership and during his reign the Tibetan government started to regain political influence over Sikkim. In 1888 the British sent a military expedition to expel Tibetan forces from Sikkim.

Accession to India
In 1975, allegations of discrimination against Nepali Hindus in Sikkim led to resentment against the Chogyal. Their instigation led to Indian Army personnel moving into Gangtok. According to Sunanda K. Datta-Ray of The Statesman, the army killed the palace guards and surrounded the palace in April 1975.

After disarming the palace, a referendum on the monarchy was held under questionable circumstances, in which the Sikkimese people supposedly overwhelmingly voted to abolish the monarchy, and the new parliament of Sikkim, led by Kazi Lhendup Dorjee, proposed a bill for Sikkim to become an Indian state, which was promptly accepted by the Government of India.

Culture and religion
In culture and religion, Sikkim was linked closely with Tibet, from which its first king migrated, and Bhutan, with which it shares borders. The presence of a large ethnic Nepali population, mainly from eastern and central Nepal, also leads to cultural linkages with Nepal.