Hello I'm new here....
I've searched the forum trying to find a similar topic but haven't found it. I have two cats that are 12 and 9 years old. They don't get along with each other even though the younger cat has been living with us for two years already. The resident cat disliked the newcomer at once, she chased her under a table and didn't allow her to the food bowl and litter box. We had to separate them into different rooms. That's how we've lived for the past two years. We have to keep the doors closed otherwise the older cat will keep chasing and harassing the new one, they'll fight and hiss at each other. Feline armoured camp.
Is there a chance to befriend them now when they've lived in separate rooms for such a long time? How can we do that?
I've searched the forum trying to find a similar topic but haven't found it. I have two cats that are 12 and 9 years old. They don't get along with each other even though the younger cat has been living with us for two years already. The resident cat disliked the newcomer at once, she chased her under a table and didn't allow her to the food bowl and litter box. We had to separate them into different rooms. That's how we've lived for the past two years. We have to keep the doors closed otherwise the older cat will keep chasing and harassing the new one, they'll fight and hiss at each other. Feline armoured camp.

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So shortly there was this couple, they had two cats that were really fine with eachother until they moved to a new house, thats when the male cat started attacking the female non stop! they had to separate her to a different room and she had to live there by her self for so long. Basically what happened is they just moved to a whole new territory and there was no clear "owner" so they were contently fighting, I know yours is a new cat but these two became complete strangers when they got to the new territory so its basically the same issue. So he had them install a screen door, some kind of screen where they can only smell and hear each other through but they can't get to each other, and had them eat their meals as close as he could get them from both sides of the door, then he slowly let them also see each other and little by little he got them to share a meal together without killing each other and assosiating each others company, smell, look and sound with good things (feeding time). when they were find through the door he let them together and surly enough they were back to being best friends!
So I would try this I would per say go and install a screen door you could get just a baby gate (high enough so they cant jump through) and do it that way but just do it step by step. placing a newcomer in a claimed territory is probably gonna end up with one attacking the other so its better to let them know each other the right way before they proceed to killing each other!
Hope this helped and let me know about the episode I can send it to you if you want, if you want to buy it on amazon its only $1.99 this specific one is episode 5 season 2 and its called "Cat Fight!".
Janis thanks for your reply too. Yes, they are neutered.
Punkybrewster that's a good think to know.
By the way this weekend we're going to go and get a screen door. I'm so excited! I really want my girls to be on friendly terms. So badly do I want it!