The India-China border dispute is an ongoing territorial conflict over the sovereignty of two large, separated regions along their shared Himalayan frontier, which India claims is approximately 3,488 km long. The dispute is a legacy of British colonial-era border agreements and the lack of a mutually recognized, formally demarcated boundary.
The conflict's origin lies in the 19th and early 20th centuries, when British India proposed different boundary lines. In the western sector, the dispute centers on Aksai Chin, a high-altitude region controlled by China but claimed by India based on the 1865 Johnson Line. China, however, adheres to the 1899 Macartney-MacDonald Line, which places Aksai Chin in its territory. In the eastern sector, the dispute is over Arunachal Pradesh (referred to by China as Zangnan or Southern Tibet), which India administers based on the McMahon Line. This line was drawn in 1914 during the Simla Convention between British India and Tibet, but China rejected it, arguing Tibet was not sovereign to sign the treaty.
The mechanism of the dispute is the Line of Actual Control (LAC), a notional demarcation separating Indian-controlled territory from Chinese-controlled territory. The term was introduced by Chinese Premier Zhou Enlai in 1959 and came to refer to the line formed after the 1962 Sino-Indian War. The LAC is not a legally recognized border, and both countries disagree on its exact alignment, leading to frequent standoffs.
The dispute connects to the 1962 Sino-Indian War, which was fought in both disputed areas. More recently, the dispute changed significantly with the violent clash in the Galwan Valley in Eastern Ladakh in June 2020, which resulted in the first combat fatalities since 1975 and led to a breakdown in trust. This event triggered a massive military build-up and fast-tracked border infrastructure development by India along the LAC. While disengagement has occurred in friction points like Galwan, Pangong Tso, and Gogra-Hot Springs, the core disagreement over the boundary remains unchanged.