In the year 1947, India won Independence which was accompanied by a dreadful partition of the nation. Soon afterwards, in 1949, the People's Republic of China (PRC) was established. One of the most basic policies for the Indian government was that of maintaining cordial relations with China, reviving its ancient friendly ties. India was among the first nations to grant diplomatic recognition to the newly-created People's Republic of China.
However, in 1950, the Chinese People's Liberation Army annexed Tibet and later the Chinese extended their influence by building a road in 1956–67 and placing border posts in Aksai Chin. India found out after the road was completed, protested against these moves and decided to look for a diplomatic solution to ensure a stable Sino-Indian border. To resolve any doubts about the Indian position, Prime Minister Jawaharlal Nehru declared in parliament that India regarded the McMahon Line as its official border. The Chinese expressed no concern at this statement, and in 1951 and 1952, the government of China asserted that there were no frontier issues to be taken up with India.
In 1954, China and India negotiated the Five Principles of Peaceful Coexistence, by which the two nations agreed to abide in settling their disputes. India presented a frontier map which was accepted by China, and the Indian government under Prime Minister Nehru promoted the slogan Hindi-Chini bhai-bhai (Indians and Chinese are brothers). Chinese Premier Zhou Enlai, in November 1956, again repeated Chinese assurances that the People's Republic had no claims on Indian territory, although official Chinese maps showed 120,000 square kilometres (46,000 sq mi) of territory claimed by India as Chinese.
This apparent progress in relations suffered a major setback when, in 1959, the Tibetan religious leader at the time, the 14th Dalai Lama, who fled Lhasa after a failed Tibetan uprising against Chinese rule, was accommodated in India. The Chairman of the Chinese Communist Party, Mao Zedong, was enraged and asked the Xinhua News Agency to produce false reports on Indian expansionists operating in Tibet.
Border disputes started. In August 1959, the People's Liberation Army took an Indian prisoner at Longju, and two months later in Aksai Chin, a clash led to the death of nine Indian frontier policemen.
As a consequence of their non-recognition of the McMahon Line, China's maps showed both the North East Frontier Area (NEFA) and Aksai Chin to be Chinese territory. In 1960, Zhou Enlai, Premier of the People's Republic of China, unofficially suggested that India drop its claims to Aksai Chin in return for a Chinese withdrawal of claims over NEFA. Adhering to his stated position, Nehru believed that China did not have a legitimate claim over either of these territories, and thus was not ready to concede them.
Nehru's stance was perceived in China as Indian opposition to Chinese rule in Tibet. Nehru declined to conduct any negotiations on the boundary until Chinese troops withdrew from Aksai Chin, a position supported by the international community. India produced numerous reports on the negotiations, and translated Chinese reports into English to help inform the international debate. China claimed that India was securing its lines in order to continue its "grand plans in Tibet".
By 1961, India started sending Indian troops and border patrols into disputed areas. This program created both skirmishes and deteriorating relations between India and China. The aim of this policy was to create outposts behind advancing Chinese troops to interdict their supplies, forcing them north of the disputed line. There were eventually 60 such outposts, including 43 north of the McMahon Line, to which India claimed sovereignty. China viewed this as further confirmation of Indian expansionist plans directed towards Tibet. Implementation of this Forward Policy was intended to provide evidence of Indian occupation in the previously unoccupied region through which Chinese troops had been patrolling.
Various border conflicts and military incidents between India and China flared up throughout the summer and autumn of 1962. On 10 July 1962, 350 Chinese troops surrounded an Indian occupied post in Chushul (north of the McMahon Line) but withdrew after a heated argument via loudspeaker. In August, the Chinese military improved its combat readiness along the McMahon Line and began stockpiling ammunition, weapons and gasoline.
In June 1962, Indian forces established an outpost at Dhola, on the southern slopes of the Thag La Ridge. Dhola lay north of the McMahon Line but south of the ridges along which India interpreted the McMahon Line to run. In August, China issued diplomatic protests and began occupying positions at the top of Thag La. On 8 September, a 60-strong PLA unit descended to the south side of the ridge and occupied positions that dominated one of the Indian posts at Dhola. By the time the Indian battalion reached the point of conflict, Chinese units controlled both banks of the Namka Chu River. On 20 September, Chinese troops threw grenades at Indian troops and a firefight developed, triggering a long series of skirmishes for the rest of September.
On 10 October, a Punjabi patrol of 50 troops to Yumtso La were met by an emplaced Chinese position of some 1,000 soldiers. Indian troops were in no position for battle, as Yumtso La was 16,000 feet above sea level and there was no artillery support planned for the troops. The Chinese troops opened fire on the Indians under their belief that they were north of the McMahon Line. The Indians were surrounded by Chinese positions which used mortar fire. However, they managed to hold off the first Chinese assault, inflicting heavy casualties.
At this point, the Indian troops were in a position to push the Chinese back with mortar and machine gun fire. However, Brigadier Dalvi opted not to fire, as it would mean decimating the Rajput who were still in the area of the Chinese regrouping. They helplessly watched the Chinese ready themselves for a second assault. In the second Chinese assault, the Indians began their retreat, realising the situation was hopeless. The Indian patrol suffered 25 casualties but bravely managed to kill 33 Chinese soldiers. However, the Chinese were in better positions. The Chinese troops held their fire as the Indians retreated. This was the first occurrence of heavy fighting in the war. The war had begun.