Clash of Eagles by Alan Smale
It is the year 1218 AD and the Roman Empire has come to North America. In its endless drive for land and gold the Empire has sent Praetor Gaius Marcellinus and the 33rd Legion to this new land to conquer it and claim it for Rome.
But these are not the settled lands of the Roman Empire and as the 33rd Legion marches further into the continent’s interior it comes into conflict with a civilization like nothing the legionaries have ever seen and it is soon massacred by warriors using weapons and tactics like none they have ever faced. The only survivor is Gaius Marcellinus, kept alive in the hope that his military knowledge will prove useful to his captors.
The world is changing and the distant threat of the encroaching Roman Empire is not the only threat that the people of Cahokia face. It may be that the knowledge possessed by Gaius Marcellinus may be the only thing that stands between them and their utter destruction.