Sentence:  He exhorts the emperor to revive the courage of his subjects by the example of manly virtue; to banish luxury from the court and from the camp; to substitute in the place of the Barbarian <WSD>mercenaries</WSD>, an army of men interested in the defence of their laws and of their property 
Meaning of the word marked with <WSD> tags:  A person employed to fight in an armed conflict who is not a member of the state or military group for which they are fighting and whose primary motivation is private gain.