What metaphors are used in Pao: A Novel by Kerry Young?

Medieval warrior and writer Sun Tzu is the author of the book The Art of War, used by both Zhang and Pao as a manual and/or inspiration for how they run their criminal organizations, business, and personal relationships. He never actually appears in the book, but his presence is strongly felt by both Pao and the reader, as the former seems to rarely, if ever, make a decision without considering Sun Tzu's teachings and the latter is exposed, several times, to the book's thematic and/or metaphoric implications by Sun Tzu's interjected comments.