This can be any kind of conflict, not just the kind with weapons. This includes classics such as A Tale of Two Cities by Dickens, and The Iliad and The Odyssey, both by Homer. This can also be a clear cut good versus evil book, but not everything is as simple as that. Sometimes, the battle can be more verbal than anything else. In a lot of realistic fiction, where they pit the protagonist against mean bullies, that is also a war of sorts. A more recent series with The Great Battle theme is A Song of Ice and Fire, otherwise known as Game of Thrones. The Hobbit and Lord of the Rings fit under this category as well. The James Patterson series Witch and Wizard series fits here. The Secret Benedict Society fits here because of the infamous battle between the kids and the nefarious Ledroptha Curtain.