Consider the prolonged peace when Rome has unquestioned naval superiority, or when Britain has massive naval advantage in the 1800s. When one nation is so much stronger than any group of nations put together (on the seas in this case, but the same idea for a land army), there is an understanding that it would be futile to challenge. We just have to cross our fingers that the overwhelmingly powerful nation of the time has a strong moral conscience. (Which is rare).