Getting older sucks. I have fuzzy memories of a rather long or epic length story hopefully on THIS site where teens fight the war(s). Two opposing veteran groups join sides and basically AWOL and break away to find a place of their own. Story goes through the tribulations of them running and being ruthlessly hunted by their former armies and other authorities.
The only thing that keeps bouncing around in my head is something about a fountain, and that one of the girls is a bonafide badass with a bunch of kills shown by something on her uniform that gives many of the people they come across pause.
I'm hoping it was (is) on this site and I'm just missing it but any help would be appreciated. Please PM me if you know and it's on another.