one who had already fought his battles, and fought them not without glory
This seems to be an allusion to some lines from one of Horace’s poems. In Latin the lines read “Vixi puellis nuper idoneus / et militaui non sine gloria” and can be translated into English as “I have recently lived suitable for girls, and fought not without glory.” [MD 2005]
Frank Gresham believes that he–like the speaker in Horace’s poem–is experienced in relations between men and women; consequently, he is frustrated when he feels that Miss Dunstable is talking to him as one might talk to an inexperienced youngster. [RR 2011]
Sources: Horace, Ode 3.26.1-2.