McMahon Line

McMahon Line, de facto boundary between India and China in northeastern India, specifically marking the border between the Indian state of Arunachal Pradesh and the Chinese autonomous region of Tibet. It was negotiated between Tibet, China and the British Empire at the end of the Shimla Convention (1913–14) and was named for the chief British negotiator, Sir Henry McMahon. The line is 550 miles (890 km) and runs from the eastern border of Bhutan along the crest of the Himalayas to the great bend in the Brahmaputra River where that river emerges from its Tibetan course into the Assam Valley. The line continues eastward and ends at the northwestern tip of Myanmar (Burma).

The Shimla Convention (1913–14)

In October 1913 representatives from the British Empire, China, and Tibet gathered at the hill station of Shimla (now in the Indian state of Himachal Pradesh) at the foothills of the Himalayas to negotiate territorial boundaries. The treaty divided Tibet into inner and outer territories, the latter to be controlled by the Tibetan government in Lhasa under Chinese suzerainty. It also charted the India-Tibet border, called the McMahon Line. Although the British Empire and Tibet accepted the terms, China refused to sign the principal agreement because it believed that Tibet was an integral part of China and had no power to enter into treaties.

China and the Sino-Indian War of 1962

In 1949 Mao Zedong and his communist forces overthrew the government and proclaimed the People’s Republic of China. Under Mao, China did not recognize the validity of several pre-1949 treaties, including the Shimla Convention, which it had never recognized. In a letter addressed to Indian Prime Minister Jawaharlal Nehru in 1959, Chinese premier Zhou Enlai noted that the Shimla Convention was part of Britain’s “imperialist aggression” against China. Zhou wrote:

The so-called McMahon Line was a product of the British policy of aggression against the Tibet Region of China and has never been recognised by any Chinese Central Government and is therefore decidedly illegal.

Frequent skirmishes along the McMahon Line contributed to the Sino-Indian War of 1962, which spilled into the Aksai Chin region in Kashmir as well. During the war Chinese troops crossed the McMahon Line and established positions in the Indian-controlled North East Frontier Agency (NEFA; now the state of Arunachal Pradesh), only to later declare a unilateral ceasefire and withdraw behind the McMahon Line.

Cold peace

Although India and China have not engaged in a full-blown war since 1962, tensions persist despite the establishment of several mechanisms to mitigate the conflict, including through diplomatic and military channels. China does not recognize the Shimla Convention and the McMahon Line, asserting that Arunachal Pradesh is part of its territory. India upholds the McMahon Line as the official boundary with China. In 2023 a bipartisan resolution was introduced in the U.S. Senate recognizing the McMahon Line as the boundary between Arunachal Pradesh and China.