I like your first statement.It wouldn't. Diplomacy, and military force are orthogonal. While wars end with diplomacy, diplomats don't end wars.
Countries start wars when they are at the apex economically, or when they think they need to start a war before the economy gets worse.
This way, the Second Chinese Civil War will start when China will get few years of good growth.
Putin started a war for his ego and legacy, and didn't restrain himself because he knew the threat of nuclear weapons would keep NATO at bay. Xi worries me for the same reason. He seems to want his legacy to be absorbing Taiwan. Diplomacy can't do anything about personal egos. Diplomacy can and has patched up our relationships a little with our allies, but to my untrained eyes diplomacy has done nothing of real value with Russia and China.