Rebel - The Raven and the Eagle series

At last, the Roman Empire is winning one of its most savage wars. King Pinnes is dead. The Pannonian tribes have surrendered. Only the Dalmatians under Bato remain in the fight, and this brutal leader holds the life of a former Roman standard bearer in his hands. Corvus is spared only on condition that he continues to fight against Rome as a rebel, but his enemies are everywhere. Not only do the Romans want his head, but the treacherous Ziva is a constant threat. The entire might of Rome is directed against Bato's army. And there, in the fire of the rebellion's last stand, Corvus must face his greatest betrayer - Marcus.