Sarmatian. The Parthian Chronicles, #13

War is a jealous lover who is reluctant to release me from her embrace. Pacorus, now retired from the politics of Parthia, embarks on a journey to request the high king find a place in the empire for his Egyptian protégé, who has been offered the governorship of Roman-controlled Egypt, as well as to discover the whereabouts of his former squire. But Queen Gallia's assassins have unwittingly set in motion a sequence of events that will plunge the empire into peril, as well as endangering the King of Dura himself.
When an invading horde of barbarians sweeps into Parthia from the north and crushes everything in its path, Pacorus is once again forced to unsheathe his sword. But old allies cannot be relied upon and Pacorus is not the great warlord of old. With an untrustworthy high king and a cunning adversary to face, he is soon faced with his greatest challenge: saving the Parthian Empire itself.'Sarmatian' is the thirteenth volume in the Parthian Chronicles series and follows on from 'Lord of War'.
A map of the Parthian Empire in the 1st century BC can be found on the maps page of my website.