How Cat vs cat aggression, angry are shown to each other.

cats — like aggression and fighting — can come on suddenly or gradually. When they happen, it can be stressful for you and your cat.Show more

Any sudden change in your cat’s behavior could be a sign of an underlying medical condition. Diseases such as hyperthyroidism, osteoarthritis, dental disease, and central nervous system problems may cause aggression. See a veterinarian to make sure your cat is healthy.

If your veterinarian rules out medical problems, you’ll need to identify the cause of the aggression to develop a behavior modification plan with your vet (or other professional)".

Types and Causes of Feline Aggression
If there’s no medical reason for your cat acting aggressively, one of the following could be in play:

Fear aggression. Fear aggression may occur in situations that make your cat feel threatened or trapped. If your cat feels afraid, they may act in aggressive ways to defend themselves.

Maternal aggression. Maternal aggression may happen when an animal or person approaches a mother cat and her kittens. The mother cat may growl or hiss, swat at, chase, or even try to bite another cat who gets too close, even if they typically get along. Maternal aggression usually goes away after the kittens are weaned from nursing. If a female cat is maternally aggressive, consider spay ing to prevent any more litters.