Initially, the Indo-Burmese border had been drawn based on surveys conducted under the Topographical Survey of British India as early as 1912, following the highest ridge from the Hkakabo Razi (alt. ; the highest point in Myanmar) at the junction with the Chinese border in the north, to the Chittagong Hills in Bangladesh according to a "combination of ridges, watershed and highest crests". Later, during World War II, G.D.L. Millar's diary recalls the escape of a party of 150 European, Indian and Kachin officials and civilians fleeing the advance of the Japanese in May 1942. They went from Putao (Kachin) to Margherita (Assam) via the Chaukan Pass, and followed the valley of the Noa-dihing river. Millar records that over a hundred miles of the Chaukan Pass, "there was no trace of man" either Lisu or any other tribe. The border negotiations with China that led to the 1962 Sino-Indian War, and the intrusion of Chinese troops into the Indian State of Arunachal Pradesh, propelled the Government of India to secure its international borders in the North East region, defined as per the Topographical Survey of British India. The Assam Rifles Regiments who took control of the border area hired labourers from various tribes, including Lisus, to built the air strip at Vijoynagar. In 1969–70, 200 families were settled in the area. In 2010, the population was estimated at 5500 including Gorkhali Jawan(Ex-Assam Rifles Pensioners and Lisus/Yobin.