Sons of the Citadel. The Parthian Chronicles, #6

Did you think the gods would leave you alone, Pacorus? Did you truly believe the Romans would forget the humiliation of Carrhae and not rest until they had won back their lost eagles?Pacorus had believed the defeat of Crassus would signal the end of Roman interest in Parthia and for many years his kingdom knew peace and prosperity. But the vindictiveness of Queen Cleopatra of Egypt draws him and the Parthians into a new war, one in which they would be fighting for their very existence when her husband Mark Antony invades the empire at the head of over one hundred thousand men.
At first the new high king of the Parthian Empire refuses the assistance of Pacorus and his famed army, but as disaster follows disaster only Dura's soldiers can save the empire from being swallowed whole by the Romans. An older, wiser Pacorus is forced to take the field against the might of Rome once more in a war that will be a turning point for him, the empire and his family.