Why did the Japanese Kwantung Army defend the Northeast? What is the purpose of immigrating many "Japanese brides"?

Because the northeast is the biggest springboard on the border of China, we can attack and retreat. This can be used as a military stronghold. The only mistake is that summer is short and winter is long in this area, and the climate is dry and cold. Not suitable for living and farming. However, in order to ensure that the garrison can stay in the local area for a long time, many female immigrants, including female soldiers, were sent to help guard the local public security. Since we are stationed in the army, of course, we should send female players to live here.