fight club coming back!
Basically, there are two types of battles in RPG: Duels and Slaughter. They are completely different, and should be GMed in a different way. But, before we begin let me state what I consider a duel and a slaughter.

A duel is a fight with some strict rules and not many people are taking part in the fight. Two, Three, maybe four or five fighters. Two gladiators fighting on an arena is a good example.

A slaughter is a battle of many people, ten and more. It is chaotic, quick, “mass”, in which you don’t know who hit you and if the guy you just attacked was a friend or foe. A scuffle in a tavern or a medieval-type battle of many knights are good examples of a slaughter.
Now, let’s concentrate on how we should GM such fights.
The key thing about playing a “duel” is that your descriptions should be long and detailed. Tell the players about every blow, where and how they were hit or how did they stroked the enemy. Describe pain and wounds, blood and bruises. Emotions, anger, fury, fear… You can even describe fighters deeper feelings if you want.

A slaughter is a complete opposite of the duel. As I mentioned before, it is quick and chaotic. You should make your descriptions as short as possible and concentrate on the speed of the battle. Try to deliver the ambiance of a chaotic battle, using single words as a description (crack! pain! blow!), short sentences (a stroke in your head! blood drenching your eyes! you feel like your leg got broken) or using tone of your voice (quick, nervous, loud).

Now, the most important thing about “slaughter” is the speed of the battle. We want our players to have to act quickly, make mistakes, don’t analyse their actions. There are several ways you can do it. if you are a good storyteller, they should naturally act quickly because of your voice, the ambiance of a battle, where every moment of hesitations can cost them their lifes. If they still carefully analyse their steps, you can use a stop-watch and give each of them like 20 second to declare their actions. After the time they just lose their turn.

Finally, there are fights which aren’t duels nor slaughter, a fight of 4 PCs against one monster for example. In such situations you should try to combine both ways of GMing, depending on what reactions from the players you want to achieve (tactical sense / chaotic fight).

See also Fight Club - Introduction and Fight Club - “No one wants to die.”

image by Tsune D. Orozco Toda