I have only had one of my students try to fight. He is small, and his intent was obvious, so it wasn't hard to hold him back. It's Taiwan, and they were yelling Chinese, so I'm not sure. But, I believe the one being attacked was the aggressor. The aggressor was larger, and laughed at the attack.
The attacker is a student who frequently cries in my class. He misbehaves a lot. So I punish him. He cries. He gets angry for some other reason he cries. This student needs to learn some other tactics. Incidentally, the bullied often become bullies themselves. Maybe I can use this as an opportunity to help him learn some better strategies.
Also, I dislike the complete objection to the bullied student being taught to do something different. If a person is frequently treated badly by numerous people, maybe they ARE doing something wrong. The bully should still be punished, but that doesn't mean you can't talk to the bullied.