In the late Ming Dynasty, some westerners began to enter Tibet for exploration and preaching.

In the 19th century, some foreign countries such as Britain, Russia and Japan sent explorers or preachers to Tibet for various reasons.

In 1814，the British East India Company launched a war of aggression in Nepal in an attempt to open a passage to Tibet. However, the Qing Dynasty was too weak to help Nepal resist invasion. Instead, it had to watch China's neighboring countries like Bhutan and Sikkim invaded by the British troops. In only a few years, the British forces had spread to the Himalayan area, threatening Tibet under the control of the Qing Dynasty.

Photo shows the office of the Grand Minister Resident of Tibet, Lhasa.

In 1890, the Qing Government's representative Taisheng and Henry Charles Keith Lansdowne, governor general of India, signed the Convention between Great Britain and China Relating to Sikkim and Tibet, in which the Chinese government recognized British protection of Sikkim and ceded a large tract of territory to Britain.

At the end of 1903, the British troops equipped with 3,000 modern weapons invaded Tibet or the second time and occupied Lhasa, capital of Tibet. In July 1904, as the 13th Dalai Lama ran away, they forced the representatives of the three major monasteries in Tibet-the Drepung, Sera and Gandain to sign "the Lhasa Treaty" in the Potala Palace. However, as the Grand Minister Resident of Tibet Youtai didn't sign it under the attendants' persuasion, the Central Government of the Qing Dynasty declared the convention invalid.

Since then, all Tibet's ports of entry had to open to the British, who were also entitled to run schools for noble children in Indian border areas and southwestern Tibet's Gyangze County. Besides, post, telecommunications and custom offices were all in the hands of the British.

It is Britain that invaded Tibet then. Even so, the British imperialists still asked the Tibet local government to pay reparations. In 1908, the Central Government of the Qing Dynasty paid 1.2 million liang (37,500 kg) silver to Britain. Afterwards, the British Expeditionary Force (BEF) withdrew from Tibet.

In January, 1912, the following year after the Revolution of 1911 which overthrew the Qing Dynasty, Sun Yat-sen, the first provisional president of the Republic of China (ROC), declared to the whole world in his inauguration statement: "The foundation of the country lies in the people, and the unification of lands inhabited by the Han, Manchu, Mongol, Hui and Tibetan people into one country means the unification of the Han, Manchu, Mongol, Hui and Tibetan ethnic groups. This is what we refer to national unification." The first constitution of the ROC also stipulated in explicit terms that Tibet is part of China.

In 1913, taking advantage of the fact that Yuan Shikai, who usurped the presidency of the ROC, was eager to get foreign diplomatic recognition and international loans, the British government forced the Beijing government to participate in a tripartite conference of China, Britain and Tibet, namely the Simla Conference held at the behest of the British government. 

Photo shows representatives attending the Simla Conference: the Foreign Secretary of the British Indian Government Henry McMahon (in the middle of the front row), representative of the Chinese Government Chen Yifan (3rd L), representative of the Tibet local government Xarta Lhunshi (3rd R).

Instigated by Henry McMahon, the Foreign Secretary of the British Indian Government, representative of the Tibet local government Xarta Lhunshi spelt out the "Tibet's Independence" plan, to the rejection by Chen Yifan, representative of China's Central Government. Then the British representative proposed dividing Tibet into two parts: inner Tibet and outer Tibet, which was rejected as well. As a result, the conference broke down because the representative of China's central government refused to sign the treaty.

In 1953, Yang Gongsu, the former assistant of the Central Government in Tibet's Foreign Affairs, saw the map with the "the McMahon Line" before he left Lhasa for Sino-Indian diplomatic negotiation in Beijing. He recalled: "It is the first time that we saw the McMahon Line, because the map has never been made public since it was drawn. The map contains no latitude or longitude, it was just a roughly-drawn heavy line as the boundary line, with McMahon and Xarta's signatures."

The governing of Tibet by the Central Government of the ROC was ineffective for some time. Consequently, Tibet's upper class propped up by foreign imperialists started to engage in separatist activities: blocking vital communication lines linking Tibet with the rest of China; stipulating that the inlanders had to enter Tibet via India after obtaining visa from the British Indian government.

In 1924, the British in Lhasa attempted to incite the Tibetan army's commander Carong to stage a mutiny to overthrow the 13th Dalai Lama and set up a pro-Britain regime. However, having detected the scheme, the 13th Dalai Lama removed Carong from all his posts.

The 13th Dalai Lama vowed many times in his late years to support national unification and the Central Government. In 1930, when meeting with Liu Manqing, investigator sent by the Nationalist Government to Lhasa, he said sincerely: "The British really have the desire to lure me, but I know we must never lose sovereignty. What I seek most is China's peaceful unification."

Photo shows the 13th Dalai Lama.

After the 13th Dalai Lama died in 1933, separatist activities of Tibet independence forces in the Tibet's local government became increasingly rampant. In October 1942, the local government of Tibet announced the establishment of the Tibet's Foreign Affairs Bureau, treating Tibet as an independent state as China.

Upon hearing this news, the Central Government immediately cabled its Tibet Office: this matter concerns China's sovereignty over Tibet. It ordered the office to handle matters as before, and not to have any relations with the so-called Tibet's Foreign Affairs Bureau.

In 1946 before the Independence of India, H. E. Richardson, the British representative in Lhasa, incited Tibet's local government to join the Pan-Asian Convention, which he called the best opportunity for Tibet's appearance as an independent state. Then the Tibet's local government sent three delegates to this convention held in New Delhi, India in March 1947.

At the meeting venue, the representatives of the Chinese government found that the Tibetan "Snow Lion Flag" mixed with the national flags of various countries and that Tibet was absent in China in the map of Asia as hung on the rostrum. The Chinese representatives lodged protests against such an act, with the result that the India side removed the "Snow Lion Flag" and changed the map afterwards.