During the Republic of China period, China was still oppressed by the great powers and signed many unequal treaties.
In 1921 (the decade of the Republic of China), the Soviet Union instigated the independence of the Tangnu Uliang Sea, and the Republic of China, which was in the midst of warlord melee, had no time to take care of the north, making the Tangnu UliangHai area out of control.
Donnu Uriang Sea area
In 1944 (the 33rd year of the Republic of China), the Soviet Union annexed the Tangnu Uliang Sea, with a total area of about 170,000 square kilometers.
In 1945 (the thirty-fourth year of the Republic of China), the Soviet Union, Britain and the United States concluded the Yalta Agreement, and in October of the same year, Outer Mongolia held a so-called independence referendum (the Soviet army also participated in the vote). The National Government was forced to recognize its so-called "independence". It has an area of about 1.44 million square kilometers.
Outer Mongolia
In addition, China has lost many islands such as the Black Blind Island and the Ryukyu Islands, which were returned by Russia in 2004 and the Ryukyu Islands were given directly to Japan by Chiang Kai-shek under ill jurisdiction.
Location map of the Ryukyu Islands
According to incomplete statistics alone, from the Qing Dynasty to the Republic of China in 1945, China lost control of a total of more than 5.88 million square kilometers of land from various unequal treaties and changes, and it was not until after the New China that it slowly regained its territory.
I believe that in the near future, we will restore the original territory and make the country rich and the people strong.