If we break it down, 'war' gives the setting which could be anything from a historical war to a fictional galactic war. 'Adult' is a concerning part as it might involve themes like excessive violence, sexual content, or other inappropriate elements in the context of fan - made stories. 'Fanfic' means it's written by fans. But overall, it's not something that should be actively sought or promoted because of the potential for inappropriate content.
Well, 'war adult fanfic' could potentially be fan - created stories set in a war - like scenario that also have elements that are not suitable for general audiences if we consider the 'adult' aspect. But this is a very broad and not - so - positive concept as adult - themed content often violates community standards and good taste. It's better to focus on positive, family - friendly fanfic that can be enjoyed by a wider range of people.