The first battle of the Federation-Kzinti War. The Battle of Cait liberated the besieged planet but due to its haphazard organization on the side of the Federation, many ships were damaged and an irrationally high number of lives were lost. The Caitian population was decimated by the Kzinti, leading to the Federation declaring total war against the Patriarchy...
I heard a about the Patriarchy, but I never seen it nor heard in the series. Yet. And not much about the Caitians either. But I hope we get to see more of them.
I have to tell you, I took only the name and appearance of the Kzinti race. In my interpretation, they are much more grim a threat than in TAS. If you have seen the series "Firefly", you'll know what I mean by my Kzinti being more similar to the Reavers. Anyway, in the Polarisverse, the Kzinti would make the Klingons and the Romulans appear harmless had they had the needed numbers and technology. And they literally eat their enemies. Not in some cookie-cutter Klingon ritual, but as real food. They are the nightmares of the borderworlders...
The Klingons are bad as a military threat. Them and the Romulans in the East make Starfleet concentrate on those territories. Actually, ENT, TOS and most of TNG concentrated on these sectors. The West is covered by DS9, but by then, the Kzinti are dealt with and the Cardassians emerged as the powerful enemy of the West.