After the People's Republic of China took control of Tibet in 1950 and suppressed a Tibetan uprising in 1959, the passes into Sikkim became a conduit for refugees from Tibet. During the 1962 Sino-Indian War, Nathu La witnessed skirmishes between soldiers of the two countries. Shortly thereafter, the passage was sealed and remained closed for more than four decades. Between 7 and 13 September 1967, China's People's Liberation Army and the Indian Army had six-day border skirmishes, including the exchange of heavy artillery fire. In 1975, Sikkim acceded to India and Nathu La became part of Indian territory. China, however, refused to acknowledge the accession at that time.