Tsona County () or Cona County () is a county in Shannan prefecture in southern part of Tibet region of China. The county lies immediately to the north of the McMahon Line agreed as the mutual border between British India and Tibet in 1914. China has not accepted the 1914 border delineation, but treats it as the Line of Actual Control (LAC). The Tsona County also borders Bhutan on its southwest. Geography Two main south-flowing rivers Nyamjang Chu and Tsona Chu flow through the county and enter India's Tawang district, where they join the Tawang Chu river. Between Nyamjang Chu and Tsona Chu lies an undulating plateau, with streams flowing west to east, often after collecting into lakes. Napa Yutso Lake and Nyapa Tso are two such large lakes. In addition, the Tsona County also contains the basins of the east-flowing rivers that form the Subansiri River. Loro Karpo Chu (the "white Loro river") in the north leads to the Jorra township. Loro Nakpo Chu (the "black Loro river") leads to the Khartak (or Kardag) township.. Tsona Dzong, the main town and the headquarters of the Tsona County, is in the plateau between Nyamjang Chu and Tsona Chu. It is 34 km north of Bum La Pass, which marks the border with the Tawang district. Immediately to the north of Bum La is the village of Shao (), whose full name Shauk Tago has been associated with Guru Padmasambhava and other Buddhist preachers over centuries. The location is mentioned in these texts as being part of "Monyul" i.e., Tawang area. History Tsona Dzong is on the historical trade route between Tibet and the Assam region of India. The original route led via the Nyamjang Chu and Tawang Chu rivers via Trashigang to Dewangiri (then in Assam, but now in the Samdrup Jongkhar District of Bhutan). 17th century In the 17th century, sectarian rivalries developed between the Gelugpa sect that was in the ascendant in Central Tibet and the Drukpa sect that got consolidated in Bhutan. The Mera lama of the Merag-Sagteng region in present day Bhutan, belonging to the Gelugpa sect, was chased out of his native village by the Drukpa forces. He fled to the neighbouring Tawang region. The people of Tawang were apparently indifferent to the sectarian divisions, and the Mera lama requested help from the governor of Tsona. However, the Tsona forces were unable to resolve the