>>That wasn't in the original brief, and I've never heard it before in the 20 years?
Yeah it's one of those unspoken "national interests" that underlies how the US plays The Great Game, but rarely states explicitly.
>>>Frankly if it's an expensive unpacifiable area, let China have it. They can sink effort into an unwinnable war instead.
If we are lucky, that will be the outcome. If the Chinese find a way to balance transit routes and natural resource extraction without somehow pissing a conservative Muslim population (while they are simultaneously oppressing Muslims in their home territory)....that could turn into a problem. If they build out links to Iran, it will not only throw a lifeline to that economically-struggling adversary, it will help China pivot away from reliance on maritime lines of communication. That maritime reliance is key to the US's strategy of threatening economic strangulation of Chinese coastal industry in the event of a conflict.
>>>Also, having consulted a map, how do you expect China to physically get there?
Via their shared border? https://en.wikipedia.org/wiki/Afghanistan%E2%80%93China_bord...
Via China's ally Pakistan, the same routes most of US military logistics took into Afghanistan for the first decade?
https://www.researchgate.net/publication/257931864_The_Afgha...