As a former ancient history teacher, I found this series had a distinct lack of objectivity, instead opting to take side of the barbarians as freedom fighters against the oppression of Rome. I also noted the historical inaccuracies others have mentioned. History is about taking a good look at all sides of the story, seeking out evidence not just on the facts, but the motives behind them. This series over-sensationalizes the barbarians while leaving out the fact that some of them did not enjoy popular support. Try Terry Jones' Barbarians for a much better idea of what really went on.
Review of Barbarians Rising
