They don't claim it because they seceded it to Russia in order to keep peace with Russia: https://www.quora.com/Why-did-China-re-take-Tibet-but-not-Mongolia/ans

They don't claim it because they seceded it to Russia in order to keep peace with Russia: https://www.quora.com/Why-did-China-re-take-Tibet-but-not-Mongolia/answer/Yu-Hsing-Chen-1 https://www.quora.com/Why-did-China-re-take-Tibet-but-not-Mo...