The Legions of Fire is Historical Fantasy: It takes place in Ancient Rome while Tiberius is emperor, only that Rome is called Carce, so that Drake doesn't get punched by history nerds. Though the history nerds would have just about zero reason for punching him – Drake majored in history (with honours) and Latin, and it shows in loving background details. All other names stayed the same as in our history – Gaul, Carthage, Germany etc, even Octavianus Augustus, so I didn't quite see the point of calling it Carce. Either do Rome, or go the Codex Alera route.