Harry Potter and the Vanguard of Dawn

Post DH AU. In a world where the Battle of Hogwarts was not won, but lost, the survivors must re-group and wage a new breed of war. Resistance is scattered across the countryside, and Harry Potter, their leader, is isolated, possibly unstable. Does any hope remain for our heroes? Can the Golden Trio go on when reduced down to 2? And what will be the cost of getting her back...