Almost all of the conflict resolution literature is about conflict between groups. This includes labor management issues, governmental issues, armed conflict, and war. Some material in the literature is about addressing marital conflict or other interpersonal issues between only two people. Most of this is about techniques for resolving conflict by improving communication skills. These include learning to use "I" statements, doing active listening, and taking "time outs" when the intensity of the conflict is too great.
These are all helpful tools and I support and teach them myself. But they are all geared toward working with the couple to teach them skills they can both use to address the mutual responsibility they have for the problems in the relationship. That is not the context in which I found myself working for much of my career as a psychotherapist.