Felidae rallies its members against a common enemy (the rabbits). Five years of cold war and six months of hot. Cats feel vaguely guilty for the next 50 years or so.
Date: 510, heavily estimated. The original mention of this was in Core Extended in the write-up of the Rabbit race, some time in the last 200 years or so. This is one of three “race wars” lodged by Felidae, the first was species against species, the second was the strike against Genotype around 150-180 AE.