Much of the book is focused on Daniel's quest for revenge against the Romans, and this colors his attitudes and outlook on life. He believes that victory will only come through war and violence; he cannot see that other methods might be more effective. Thacia, while she supports Daniel and his mission, believes that violence is not the only answer, and explains that Jesus might not intend to start a revolution.
"He says the kingdom is at hand. What else can he mean?"
"Did you ever think he might mean that the kingdom will come some other way? [...]we don't need to wait for God to care for us. He does that now. Every one of us."
(Speare, The Bronze Bow, Google Books)
The message is that war for the sake of God is not necessarily the answer. Instead of killing the Romans, it might be better to reach them intellectually and spiritually, and change their minds. Fighting for God will not make a person more righteous in God's eyes, and if done for the wrong reasons -- as in revenge -- it might actually work against a person. Instead, the peaceful sermons and grassroots spread of the message works to undermine the Roman system, and will ultimately be more effective than a decades-long war.