A long series of events triggered the Sino-Indian War in 1962. According to John W. Garver, Chinese perceptions about the Indian designs for Tibet, and the failure to demarcate a common border between China and India (including the Indian Forward Policy) were important in China's decision to fight a war with India.
Friendly relations
Numerous changes occurred in the late 1940s, with the independence of the Republic of India and the Islamic Republic of Pakistan in 1947, and the establishment of the People's Republic of China (PRC) in 1949. One of the most basic policies for the Indian government was that of maintaining cordial relations with China. The Indian government wished to revive its ancient friendly ties with China. When the PRC was declared, India was among the first countries to give it diplomatic recognition.
After coming to power, the PRC announced that its army would be occupying Tibet. India sent a letter of protest to China proposing negotiations on the Tibet issue. The newly formed PRC was more active in posting troops to the Aksai Chin border than the newly formed Indian republic was. India decided to take moves to ensure a stable Indo-Chinese border. In August 1950, China expressed its gratitude to India's attempts to "stabilize the Indo-Chinese border". To clear any doubts or ambiguities, Prime Minister Nehru stated in Parliament in 1950 that "Our maps show that the McMahon Line is our boundary and that is our boundary...we stand by that boundary and we will not let anyone else come across that boundary". China expressed no concerns at these statements.
By 1951, China had extended numerous posts in Aksai Chin. The Indian government, on the other hand, concentrated its military efforts on stopping Ladakh from being taken by Pakistani troops and did not establish itself in Aksai Chin. On various occasions in 1951 and 1952, however, the government of China expressed the idea that there were no frontier issues between India and Chinese Tibet to be worried about.
Later, in September 1951, India declined to attend a conference in San Francisco for the conclusion of a peace treaty with Japan because China, which India viewed as an important factor in this treaty, was not invited because of its status as an international pariah. In the coming years India strove to become China's representative in world matters, as China had been isolated from many issues. India vigorously pressed, since the start of the 1950s, for the PRC to be included within the UN.
The People's Liberation Army defeated the Tibetan army in a battle at Chamdo in 1950 and Lhasa recognized Chinese sovereignty over Tibet in 1951. The Indian army asserted control of Tawang at this time, overcoming some armed resistance and expelling its Tibetan administrators. In 1954, China and India concluded the Five Principles of Peaceful Coexistence under which India acknowledged Chinese sovereignty in Tibet. Indian negotiators presented a frontier map to the Chinese that included the McMahon Line and the Chinese side did not object. At this time, the Indian government under Prime Minister Nehru promoted the slogan Hindi-Chini bhai-bhai (India and China are brothers).
In 1954, B. R. Ambedkar in the Indian Upper House, said that by "allowing the Chinese to take possession of Lhasa, the Prime Minister has practically helped them bring their border down to the Indian border... Aggression might well be committed by people who are always in the habit of committing aggression." Ambedkar further urged for alliance with western world and said, "is better for us to align ourselves with what we call the free nations if we believe in freedom".
On 1 July 1954 Nehru wrote a memo directing that the maps of India be revised to show definite boundaries on all frontiers, where they were previously indicated as undemarcated. The new maps also revised the boundary in the east to show the Himalayan hill crest as the boundary. In some places, this line is a few kilometres north of the McMahon Line.
Beginning in 1956, the CIA used Indian territory to recruit Tibetan guerrillas to fight Chinese troops, with a base in Kalimpong, India. The Indian public was outraged when it learned in 1958 that China had built a road between Xinjiang and Tibet through Indian territory in Aksai Chin (historically a part of Indian state of Ladakh).
