Jack is a likable orphan from the first Robotech War who joined the REF to get revenge against Zentraedi. However, he has learned to live with his grief and move forward, rather than long for vengeance. Jack is a true REF knight who has adopted the REF code of ethics as his own moral code. His only bad traits are being overzealous, lacks self-control and often acting on his heart and not his head.
NOTE: In the script outline, Jack recognizes Col. Edwards to be the treacherous fiend he is, and the two have several verbal confrontations. Jack's friendship with Rick Hunter is enough reason for Col. Edwards to hate him, and Jack's suspicions ("I'll be watching you Edwards.") puts Airman baker on the top of Edwards hate list, right under Rick, Lisa and Max.
Jack is also in love with Karen Penn. It is a tumultuous, one-sided relationship. Jack joins the Sentinels, along with Rick, Max, Lisa, Karen, Miriya, and Wolfe.