Keep the cats separated at first
Swap their bedding to mix scents
Feed them on opposite sides of a closed door
Let them see each other briefly through a barrier
Reward calm behavior with treats
Increase supervised face-to-face time gradually
Provide separate food, water, litter boxes, and resting spots
Add vertical spaces and hiding places
Play with each cat individually every day
Avoid forcing interactions
Interrupt chasing or fighting calmly and immediately
Use pheromone diffusers if needed
Keep routines consistent
Neuter or spay both cats if possible
Consult a veterinarian or behaviorist if aggression continues