The best way to break up a fight is the wheelbarrow technique (you need two people though). Grab them both by the feet and move them off each other by moving them back away from each other. Make sure you have a firm grip, because if you let them go, they could go at it again. Once you have them apart you want to seperate them for about 30 minutes to let the adrenaline to stop (I'd make them go in their crates).

My two have gotten into fights before and I have learned to read their behavior and seperate them with baby gates when one of the other is getting "pissy". Learning to read their moods will help prevent things from starting. Hope this helps.

Good Luck and welcome to Pet talk. We have a lot of knowledgable people on this board that are always willing to help.