The hero dead cannot expire: The dead still play their part.

In these lines Sangster compresses a common memorial logic: physical death does not end a “hero’s” agency, because the hero’s example continues to act upon the living. “Cannot expire” suggests that heroic meaning is not bound to biological life; it persists as reputation, story, and moral pressure. The second line sharpens the claim: the dead “play their part” in an ongoing civic or national drama—shaping identity, inspiring sacrifice, or legitimizing causes. The couplet thus treats remembrance as a form of continued participation: the living keep the dead active through commemoration, and the dead, in turn, influence the living through the ideals attached to their names.