▁until ▁early - 1 9 9 0 . ▁With ▁the ▁rapp ro ch ement ▁between ▁the ▁USS R ▁and ▁China ▁in ▁the ▁late ▁ 1 9 8 0 s , ▁S ino - M ong ol ian ▁relations ▁also ▁began ▁to ▁improve . ▁Since ▁the ▁ 1 9 9 0 s , ▁China ▁has ▁become ▁Mong olia ' s ▁biggest ▁trad ing ▁partner , ▁and ▁a ▁number ▁of ▁Chinese ▁business es ▁are ▁operating ▁in ▁Mong olia . ▁ ▁Background ▁ ▁The ▁Han ▁Chinese ▁and ▁Mong ols ▁( as ▁well ▁as ▁their ▁ancest ors , ▁the ▁Pro to - M ong ols ) ▁have ▁been ▁in ▁contact ▁with ▁each ▁other ▁for ▁mill enn ia . ▁ ▁Through out ▁history , ▁Mong olia ▁and ▁China ▁have ▁had ▁complicated ▁relations . ▁The ▁Great ▁Wall ▁was ▁constructed ▁to ▁w ard ▁off ▁the ▁northern ▁nom ads ▁attacks , ▁from ▁the ▁X ion gnu ▁during ▁the ▁Q in ▁D ynast y , ▁the ▁Tur ks ▁during ▁the ▁Tang ▁D ynast y , ▁and ▁later , ▁the ▁Mong oli ans ▁and ▁Central ▁A si ans . ▁ ▁In ▁ 1 2 7 1 , ▁Mong ols ▁under ▁Kub la i ▁Khan , ▁grand son ▁of ▁G eng his ▁Khan , ▁established ▁the ▁Y uan ▁D ynast y ▁and ▁conquer ed ▁all ▁of ▁China ▁in ▁ 1 2 7 9 . ▁ ▁In ▁ 1 3 6 8 , ▁the ▁Chinese ▁under ▁the ▁M ing ▁D ynast y ▁successfully ▁exp elled ▁the ▁Mong ols ▁from ▁China ▁and ▁in ▁ 1 3