In 1888 there was a war in Sikkim between British annex Darjeeling district and Morang to British India. Sikkim had retained guarantees of independence from Britain when it became independent, and such guaranteeswere transferred to the Indian government when it gained independence in 1947. A popular vote for Sikkim to join the Indian Union failed and Indian Prime Minister Jawaharlal Nehru agreed to a special protectorate status for Sikkim. Sikkim was to be a tributary of India, in which Indian controlled its external defence, diplomacy and communication. A state council was established in 1953 to allow for constitutional government for the Chogyal, which was sustained until 1973.
In 1962, India and the People’s Republic of China went to war. Although Sikkim was an independent country, skirmishes occurred at the Nathula Pass between India Border guards and the Chinese soldiers. After the war, the ancient pass was shut down it reopened in 6 July 2006.
The old ruler Tashi Namgyal died in 1963 after suffering from cancer. The last hereditary ruler, the Chogyal Palden Thondup Namgyal ascended to the throne in 1965. Trouble began to brew for the crown even before the Chogyal assumed the throne, as Indian Prime Minister Nehru, who had carefully preserved Sikkim’s status as an independent protectorate, died in 1964. His daughter Indira Gandhi, who became Prime Minister in 1966, would have little patience for maintaining an independent Sikkim or its monarchy. The Chogyal who responded to the increased pressure by drinking, was viewed by India as politically dangerous, especially after his wife, the American socialite Hope Cooke published a journal article advocating a return of certain former sikkimese properties.
In early 1970 the anti-monarchy Sikkim National Congress Party demanded fresh elections and greater representation for the Nepalese. In 1973, anti-royalty riots in front of the palace led to a formal request for protection from India. India worried that an unstable Sikkim would invite China to act on its claims that Sikkim was part of Tibet, and therefore part of China. The Indian government appointed a Chief administrator, Mr. B.S. Das, who effectively wrested control of the country away from the Chogyal.
Frosty relations between the Chogyal and the elected Kazi (Prime Minister) Lhendup Dorji resulted in an attempt to block the meeting of the legislature. The Kazi was elected by the Council of Ministers which was unanimous in its opposition to the retention of the Monarchy.
Prime Minister Dorji appealed to the Indian Parliament for representation and change of status to statehood. On 14 April 1975, a referendum was held, in which Sikkim voted to merge with the Union of India. Sikkim became the 22nd Indian State on 26 April 1975. On 16 May 1975, Sikkim officially became a state of the Indian Union and Lhendup Dorji became head of State, Chief Minister.