idk how would they hack bitcoin? its like asking to hack every computer in the world. its nearly impossible , they called it decentralize for a reason ^_^
That is not what the OP is telling, if you look at the bitcoin network majority of the hash rate comes from China and the government can take control over these mining farms and control the entire bitcoin network, what you do not understand is that bitcoin is decentralized in nature but majority of the hashing farms are centralized and if you control these major mining farms you can control the bitcoin network.
Assuming war erupted and China manipulate mining farm to attack the network, what will happen next then? Would it bring more fund to China's war campaign? Does anyone realized that once the Bitcoin Network is hacked, trading activities will be halted? Let's assume that China gain a control over the Bitcoin network and produce millions of BTC on the new chain, who will then buy them? The effort of China to cease control of the Bitcoin network will only be in vain because, once the hack is known, all demands will eventually stop living China with worthless bags of "BTC".