 First the Lyrans and Klingons attack the Kzinti Hegemony, then the Hydrans attack them, with the understanding that they are the next target of the Lyran-Klingon Coalition.The Hydran capital falls (again), the Coalition assaults the Kzinti homeworld, and the Federation starts preparing to intervene on behalf of the Kzintis.With war against the Hydrans and Kzintis wrapping up, and the Federation mobilizing, the Klingons invade the Federation in Y171, and convince the Romulans to join the Coalition in Y173.