Start by trying to break eye contact between the upset cats. You can do this by simply standing in front of your pet.
Talk very gently and softly. When your pet looks at you, put out your hand and then speak softly. If you get a headbutt, you can then you can walk your pet home.
If your kitty is upset and is not in a state to be touched, use a soft broom. Lean this gently against your kitty’s body and push gently. Say “Home” firmly. Most likely, your pet will rush home. Then let him or her calm down a bit before you have a cuddle.
If your pet is already fighting, you have to try and minimize the danger.
First, don’t try and break them apart by hitting either of them. It could actually break their bones. Also, as you are then an additional aggressor, you yourself could be attacked.
Two, cold water may help. If cats are not literally fighting, throwing cold water might raise the aggression level and push them into fighting.
If they are fighting, a bottle of cold water over the top of them may shock them apart. If this works, stand between the cats and clap your hands to send your kitty home. Don’t try to touch your pet! He will be too upset to see it’s you and you may end up being bitten or scratched.
Three, if they are fighting, and you don’t have any water, you have to wait until they split apart. You may use a broom to very gently push your pet home. Don’t touch the strange cat at all; only work with your own pet. Try to be very gentle. Keep your voice as calm and low as you can. Dont do anything to add to the level of aggression and violence.
But most of all, remember that you are talking to a cat, not a reasoning human being. So be kind and gentle.