There is not much anyone can do if any nuclear nation decides to expand their territory by invasion. So until all nuclear weapons magically disappear then Russia or China can do what they want and there is nothing at all we can do about it. Diplomacy can do absolutely nothing to stop any nation who wants to do something like that and it never will. Talking never does any good, only action works and that is too dangerous for the world. Even if Russia or China wanted to invade our country there is not much we could do about that either.