Please, help me to identify the small territory to the northwest of Mongolia that you can see in this map:
I've searched on Google and Wikipedia with no results.
(I know it's not so small a territory. It looks about the size of Austria)
It is Tannu Tuva. When Mongolia broke out from China in 1911, this little territory was separated from China (which was in a state of internal turmoil during the first years of the Republic of China) but was not claimed by Mongolia.
In practice, Tannu Tuva was a Soviet satellite country, only the Soviet Union and Mongolia recognized it.
Stalin annexed it to the SU in 1944.
As a side note, the protests by Chinese Nationalist Government (the Kuomintang) about Soviet encroachment in it are credited as the reason for Stalin switching his support to the Communist Party of China.