Sudden outbreak of Cat Wars

[valrhona]

Everybody was getting on so nicely. Not best friends forever, but social, playing together occasionally. Companionable.
All of a sudden WARS!
Why?????
Background: both neutered, rescue, arrived same time (didn't know each other), tricky for a bit but seemed SO settled last few weeks. I'm a bit upset!

I'd guess they haven't worked out the pecking order yet. Most likely one is making a bid for position of top cat.

How long has the war been going on, valrhona , and when did it start? (As far as you know.)

I really thought they had settled mantra
We've had them since mid May. The fighting started about 2 days ago. Growling, hissing a LOT, chasing with intent. Not sure if anything physical has happened as they don't seem to do it in front of me. I just can't understand it. They seemed to have been getting closer and then this starts.