Just looking for some advise on issues we are having introducing cats.

The current resident cat we have is 11.5 years old and has been a single cat most of his life. We acquired a new cat almost 2 months ago that is just under one years old. We have tried to do the separated base camps with a child fence to keep them apart but see each other for about a month now. When we try to do supervised interaction is when we start having issues. The resident cat is very timid towards the new cat and trues to leave then the new cat attacts him. This is no play fight this is hair going everywhere and bleeding fighting.

The setup we currently are doing is the resident cat has the main floor while the new cat has the basement. We put their food bowls in sight of the baby gate separating them so the do see each other. We also have tried putting out cat calming defusers with little difference. We also do space swapping and the resident cat gets really nervous during that time.

Any help would be appreciated.