How much land has been lost to the north of Heilongjiang since Kangxi in Qing Dynasty? If these places return, will they be under the control of Heilongjiang Province or other provinces?

It covers an area of about 600,000 square kilometers to the south of Outer Xing 'an Mountains and north of Heilongjiang, and 440,000 square kilometers to the east of Wusuli River, including Sakhalin Island, with a total area of * * * 1.04 million square kilometers. The residents of these places are all Russians now. If they return to China, it will be related to whether these people will move away or become citizens of China. If they move away, there will be no one, and immigration will not happen overnight, so the province will not be built alone. If they don't move away, it is impossible to establish an autonomous province for these Russians alone in order to consolidate the frontier. The most likely situation is to adjust the administrative divisions and merge them into Heiji Province.