I'm not sure how we went from the "act" being "invest in their own defense" to "start ww3" but I am quite confident no one is complaining they are not doing that, lol.
This is also why anarchies are not very stable.
The international order, with each nation being kinda like an individual person, has few enough actors that the distinctions between "anarchy", "democracy", and "dictatorship" are blurry.