This is a loose collection of theory articles I wrote concerning combat in RPGs.
General Discussion on Combat in RPGs
The Truth about Martial Arts for Roleplayers
Threat is a concept that extends beyond just fighting to any conflict situation, where the person who is the most perceived threat gets the most attention and conflict resolution is about avoiding or redirecting Threats.
Everway and the “Elemental Warrior”
This was about running combat in Everway, but probably also applies to other very low complexity (narrative) game systems.