You know, the kind of couple where bullets figure prominently in the story of their early romance. Where "war buddy" and "significant other" are synonyms. Where if you harm either one, the other will kill you as surely as the sun rises. Likely to have a Back-to-Back Badasses moment. In Real Life, it's also the same as above -- and often, they're officers, instead. There are laws in some areas against this sort of thing if one outranks the other, although this is usually meant to prevent the superior from forcing the under-ranked into it. Examples of Battle Couple include: