A question about history.

This is the actual control line of China since the late Qing Dynasty, and it is also the southern Tibet that China has not recovered. 49 years ago and 49 years later, the China government never recognized this line. At that time, the British colonial authorities occupied nearly100000 square kilometers of land in China (McMahon Line). After the British withdrawal, India became independent, and this line was designated as the Sino-Indian border. The government of China has never recognized this line, which was illegal in colonial times. .