Realize that the border region between Kazakhstan and China is extremely mountainous. Even then, you would have to cross the formidable Gobi Desert to get to any of the really populated areas of China.
Russia can move into Kazakhstan easily from the North and West. There are plenty of roads and few obstacles. China, on the other hand, would have an enormous problem moving troops and equipment to the Kazakh border. There are only a few roads their troops could take... and everything they did would be easily seen and known about a week in advance.
Natural terrain effectively separates Kazakhstan from Chinese dominance.
Realize that the border region between Kazakhstan and China is extremely mountainous. Even then, you would have to cross the formidable Gobi Desert to get to any of the really populated areas of China.
Russia can move into Kazakhstan easily from the North and West. There are plenty of roads and few obstacles. China, on the other hand, would have an enormous problem moving troops and equipment to the Kazakh border. There are only a few roads their troops could take... and everything they did would be easily seen and known about a week in advance.
Natural terrain effectively separates Kazakhstan from Chinese dominance.