It is often hard to tell the instigator even when you are able to watch the entire thing. Cats have a very subtle body language that we can't always understand. I am assuming they are all neutered? There was some trigger you just don't know what it was...there could even be a stray coming up to your home that is causing some of this. It agitates one or the other which then causes the fighting.

There is a product called Feliway which I have had some success with in calming down one of my female cats. It is a synthetic hormone that we purchase in the plug in variety. I would also check all around for any inappropriate urination. Also Sometimes their anal glands release a small amount of fluid.When Deirdre (one of my females) smells Brianna on a blanket she gets really pissed off. This happened last night, I couldn't smell a thing on the blanket but it is one Brianna often sleeps on. I used it on the bed because with the AC I was a bit chilly. Deirdre came up on the bed and started sniffing one specific spot. She then became so angry she started snarling and hissing at ME! I had to remove the blanket before she would settle down. If Brianna had come along she would have attacked Brianna.

So first you must do some more detective work to find out why this is happening after several years of getting along. Try the Feliway and keep Critter and Colonel seperated when you are not around for a little while. Then reintroduce them slowly. Cats are very complicated creatures and it is sometimes hard to know what will set them off.

Denyce