CASCA: Sword of the Brotherhood (CASCA: The Eternal Mercenary, #35)

Captured by his sworn enemies the Brotherhood of the Lamb, Casca is forced to undertake a mission on their behalf when they threaten to kill his woman, Ayesha, unless he agrees. Left with no choice, Casca seeks to recover the holy of holies, the Spear of Longinus - his spear - from the Persians. But first their armies must be defeated in the war with the Byzantine Empire, so Casca joins the army led by the Emperor Heraclius, and takes part in the marches and battles of a war that will only end with utter defeat of one or the other. And Casca knows that should the Persians be beaten and the way left open to recover the Spear, the Brotherhood cannot be trusted to keep their word. So he must devise a plan to not only get the Spear, but to also rescue Ayesha and keep the fanatics of the Brotherhood at arm's length