What I posted is actually my version of the Sukhomlinov Effect.
The classical aphorism goes: "The country with the prettier uniforms loses."
This is entirely subjective, but the gist of "prettier uniforms" means more baubles on it.
And you're not necessarily doomed to defeat from it, after all, the Russians beat the Turks in 1878, the US defeated the Injuns, the Romans conquered the world. So it only says "the general effectiveness...is inversely related".
And this brings me to my second major change in the rule, "national military". This limits it to after the advent of the modern concept of the nation. This allows for the Romans to kick the crap out of everyone, for the Italians in general to have military dominance in the medieval and renaissance periods, and exceptions for those areas which had no conception of nation.