Bhutan's early history is steeped in mythology and remains obscure. Some of the structures provide evidence that the region has been settled as early as 2000 BC. According to a legend it was ruled by a Cooch-Behar king, Sangaldip, around the 7th century BC, but not much is known prior to the introduction of Tibetan Buddhism in the 9th century, when turmoil in Tibet forced many monks to flee to Bhutan. In the 12th century, the Drukpa Kagyupa school was established and remains the dominant form of Buddhism in Bhutan today. The country's political history is intimately tied to its religious history and relations among the various monastic schools and monasteries.
Sikkim is a state in northeastern India. It borders the Tibet Autonomous Region of China in the north and northeast, Bhutan in the east, Koshi Province of Nepal in the west, and West Bengal in the south. Sikkim is also close to the Siliguri Corridor, which borders Bangladesh. Sikkim is the least populous and second smallest among the Indian states. Situated in the Eastern Himalaya, Sikkim is notable for its biodiversity, including alpine and subtropical climates, as well as being a host to Kangchenjunga, the highest peak in India and third highest on Earth. Sikkim's capital and largest city is Gangtok. Almost 35% of the state is covered by Khangchendzonga National Park – a UNESCO World Heritage Site.
The Anglo-Nepalese War, also known as the Gorkha War, was fought between the Gorkhali army of the Kingdom of Nepal and the British forces of the East India Company. Both sides had ambitious expansion plans for the mountainous north of the Indian Subcontinent. The war ended with the signing of the Sugauli Treaty in 1816, which ceded some of the Nepalese-controlled territory to the EIC.
The Gorkha Kingdom was a member of the Chaubisi rajya, a confederation of 24 states on the Indian subcontinent ruled by the Khas people. In 1743 CE, the kingdom began a campaign of military expansion, annexing several neighbors and becoming present-day Nepal. The Gorkha Kingdom extended to the Marshyangdi River in the west, forming its border with the Kingdom of Lamjung. To the east, the kingdom extended to the Trishuli River, forming its border with the Nepal Mandala. The Gorkha Kingdom was established in 1559 CE by Prince Dravya Shah, the second son of King Yasho Brahma Shah of Lamjung. The prince replaced the Khadka chiefs who previously ruled the region.
Jelep La elevation 14,390 feet (4,390 m), is a high mountain pass between Sikkim, India and Tibet Autonomous Region, China. It is on a route that connects Lhasa to India. The pass is about 4 km (2.5 mi) south of Nathu La and is slightly higher. It was frequently used for trade between Tibet and India during the British Raj, with Kalimpong serving as the contact point. The Menmecho Lake lies below the Jelep La.
The history of Sikkim begins with the indigenous Lepcha's contact with early Tibetan settlers. Historically, Sikkim was a sovereign Monarchical State in the eastern Himalayas. Later a protectorate of India followed by a merger with India and official recognition as a state of India. Lepchas were the main inhabitants as well as the Ruler of the land up to 1641. Lepchas are generally considered to be the first people, indigenous to Sikkim also includes Darjeeling.
The Chumbi Valley, called Dromo or Tromo in Tibetan, is a valley in the Himalayas that projects southwards from the Tibetan plateau, intervening between Sikkim and Bhutan. It is coextensive with the administrative unit Yadong County in the Tibet Autonomous Region of China. The Chumbi Valley is connected to Sikkim to the southwest via the mountain passes of Nathu La and Jelep La.
The Treaty of Titalia was signed between the chogyal (monarch) of the Kingdom of Sikkim and the British East India Company (EIC). The treaty, which was negotiated by Captain Barre Latter in February 1817, guaranteed security of Sikkim by the British and returned Sikkimese land annexed by the Nepalese over the centuries. It followed the Anglo-Nepalese War, 1814–1816. In return, the British were given trading rights and rights of passage up to the Tibet frontier. The treaty was signed at Titalia, now known as Tetulia Upazila, in the Rangpur District of present-day Bangladesh. In the Gazette of Sikkim, 1894 by H.H. Risley, it was written that "by the Treaty of Titalia, British India has assumed the position of Lord's paramount of Sikkim and a title to exercise a predominant influence in that State has remained undisputed."
The History of Darjeeling covers the history of Darjeeling town and its adjoining hill areas belonging to Sikkim, but eventually part of British India so now in the Indian state of West Bengal, which is intertwined with the history of Nepal, Sikkim, Bhutan, Bengal and Great Britain. Part of the state of Sikkim, Darjeeling became part of an important buffer state between Nepal and Bhutan. The British, using the area as a sanitorium, found that the climate provided excellent tea-cultivating conditions and soon began to grow tea on the hills of Darjeeling. Darjeeling tea remains a world-renowned export from Darjeeling.
Tsugphud Namgyal (1785–1863) was king of Sikkim from 1793 to 1863. He gained independence from Nepal in 1815 and ruled under a British protectorate from 1861.
The Limbuwan–Gorkha War was a series of battles fought between the king of Gorkha and the rulers of various principalities of Limbuwan from 1771 to 1774 AD. After the conquest of Majh Kirat and Wallo Kirat by the Gorkhas, they invaded Limbuwan on two fronts. One front was in Chainpur and the second front was in Bijaypur. Bijaypur was the capital of the Morang Kingdom of Limbuwan Yakthung Laje.
Limbuwan is an area of the Himalayan region historically made up of 10 Limbu kingdoms, now part of eastern Nepal. Limbuwan means "abode of the Limbus" or "Land of the Limbus". Limbuwan was incorporated into the Kingdom of Nepal by means of a collective Gorkha-Limbuwan Treaty with the kings of the ten Limbuwan kingdoms and their ministers.
The Kingdom of Sikkim, officially Dremoshong until the 1800s, was a hereditary monarchy in the Eastern Himalayas which existed from 1642 to 16 May 1975, then it was merged with the Republic of India. It was ruled by Chogyals of the Namgyal dynasty.
The indigenous people of Sikkim are the Lepchas; the naturalized ethnic populations of Limbus, Bhutias, Kiratis, immigrants such as Indian Gorkha of Nepalese descendants who have an enduring presence in shaping the history of modern Sikkim. The indigeneity criteria for including all peoples of Sikkim and Darjeeling hills is a misnomer as it is clearly known that Lepchas are the first people who trace their origin and culture of their ethnogenesis to the historical and somewhat political geography of Sikkim history as is well documented by colonial and immigrant settler history. However many tribes preceded the migration of the colonial powers and can trace their migratory background as well as ancestral heritage and a well formed history of civilization and cultural locus that is not inherently indigenous to Sikkim.
The Nepal–Britain Treaty was first discussed in 1921 and the final treaty was signed on 21 December 1923 in Singha Durbar. The treaty was the first formal acknowledgement by the British that Nepal, as an independent nation, had the right to conduct its foreign policy in any way it saw fit and was considered to be “a great achievement of 25 years of Chandra Shumsher’s diplomacy.” The treaty was recorded in 1925 in the League of Nations.
The Convention of Calcutta or Anglo-Chinese Convention of 1890, officially the Convention Between Great Britain and China Relating to Sikkim and Tibet, was a treaty between Britain and Qing China relating to Tibet and the Kingdom of Sikkim. It was signed by Viceroy of India Lord Lansdowne and the Chinese Amban in Tibet, Sheng Tai, on 17 March 1890 in Calcutta, India. The Convention recognized a British protectorate over Sikkim and demarcated the Sikkim–Tibet border.
Doklam, called Donglang by China, is an area in Bhutan with a high plateau and a valley, lying between China's Chumbi Valley to the north, Bhutan's Ha District to the east and India's Sikkim state to the west. It has been depicted as part of Bhutan in the Bhutanese maps since 1961, but it is also claimed by China. The dispute has not been resolved despite several rounds of border negotiations between Bhutan and China. The area is of strategic importance to all three countries.
Eastern South Asia is a geographical area in the Southern Asian subregion, precisely the eastern region of the subcontinent. It includes the countries of Bangladesh, Bhutan, Nepal and India. Geographically, it lies between the Eastern Himalayas and the Bay of Bengal. Two of the world's largest rivers, the Ganges and the Brahmaputra, flow into the sea through the Bengal region. The region includes the world's highest mountainous terrain and the world's largest delta, and has a climate ranging from alpine and subalpine to subtropical and tropical. Since Nepal, Bhutan, and northeast India are landlocked, the coastlines of Bangladesh and East India serve as the principal gateways to the region.
Chumbi is a historic village in the Chumbi Valley or the Yadong County of the Tibet Autonomous Region of China. It is in the valley of Amo Chu river, where the route from Sikkim's Cho La pass meets the Amo Chu valley. The "Chumbi Valley" of the European nomenclature derives its name from the village of Chumbi. It was the administrative center of the lower Chumbi Valley until the Chinese take-over of Tibet in 1950, after which Yatung became its headquarters. Chumbi is also associated with the Sikkim's royal family, which had a summer palace in the village.
Kazis and Thikadars of Sikkim, also known as Ilakadars, were the hereditary feudal lords and the ruling class in former Kingdom of Sikkim. They had administrative and judicial powers within their respective land estates. This system existed since the establishment of the Namgyal dynasty and was further institutionalised under the period of British influence in Sikkim.
British Empire 
Sikkim