ISS
China's going through the motions. They wanna get a solid grip on space. They want to build their own space station to master building things in space. They also need to go through all the on-site research for military purposes that the US and Russia have already done ages ago, plus maybe some new stuff. They need a private place for that.
The US doesn't use the ISS for military purposes either, I don't think; the DOD does to research, but usually in independent platforms and even free-flying pressurized vehicles. Plenty of prototype sats and things too. The Clementine mission to the Moon was actually a DOD project - they needed to test a bunch of new technologies and found they could split the bill with NASA by sending it to the Moon.
...So I'm not saying the US doesn't do military research. Everyone does military stuff in space. The whole reason we're IN space is ballistic missiles. Gemini astronauts flew ballistic missiles to orbit, and even Iran's ballistic missile program developed into flying sats too.
Just... Not on the ISS. It would be kinda silly to do your top secret military research down the hall from Russia's lab, and likewise it would be pretty silly for China not to build its own private lab.