What is the Mcmahon line?

What is the Mcmahon line?
 

News: Two United States Senators, a Republican and a Democrat, have introduced a bipartisan resolution in the upper chamber of Congress reiterating that the US recognises the McMahon Line as the international boundary between China and India in Arunachal Pradesh.
 

What is the Mcmahon line?
 The McMahon Line serves as the de facto boundary between China and India in the Eastern Sector. It specifically represents the boundary between Arunachal Pradesh and Tibet, from Bhutan in the west to Myanmar in the east.
 China has historically disputed the boundary and claims the state of Arunachal Pradesh as part of the Tibetan Autonomous Region (TAR).
 

Under what circumstances was it drawn?
 The McMahon Line was drawn during the Simla Convention of 1914, officially described as the Convention Between Great Britain, China, and Tibet.
 The McMahon Line delimited the respective spheres of influence of Tibet and British India in the eastern Himalayan region in what is today India’s Northeast and northern Myanmar. The border in this region wa undefined prior to the signing of the convention.
 

What happened at the Shimla Convention of 1913-14?
 The convention attempted to settle the question of Tibet’s sovereignty and avoid further territorial disputes in the region.
 The treaty divided the Buddhist region into “Outer Tibet” and “Inner Tibet” – the former would “remain in the hands of the Tibetan Government at Lhasa under Chinese suzerainty”, though China was not allowed to interfere in its affairs.
 The latter would be under the direct jurisdiction of the newly formed Republic of China. The latter of these newly decided boundaries would later be called the McMahon Line after McMahon, the chief British negotiator.
 

Why China did not sign the convention?
 It argued that Tibet had no independent authority to enter into international agreements.
 

How was the border between British India and China decided?
 Following the “highest watershed principle”. This principle, considered to be the most logical way of drawing borders in mountainous regions by the British, basically drew the border along the highest ridge between two river plains.
 

What has the status of the McMahon line been since 1914?
 After the communists took power in 1949, they pulled China out of all international agreements and the socalled “unequal treaties” that had been imposed on it during its “century of humiliation”, and demanded a renegotiation of all its borders.
 During the 1962 Sino-Indian War, China was able to quickly overpower India and make deep inroads into Indian territory across the McMahon Line. However, its forces retreated to pre-war positions after the announcement of unilateral ceasefire.