This presents God's peace as a soldier who protects our hearts and thoughts from worrying. Here "hearts" is a metonym for a person's emotions. Alternate translation: "will be like a soldier and guard your emotions and thoughts in Christ" or "will protect you in Christ and will keep you from worrying about the troubles of this life" (See: [[rc://en/ta/man/translate/figs-personification]] and [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-explicit]])