Duty is central to Antony and Cleopatra because it exemplifies the honor that is so central to being in a position of power. Duty to the state is held up for view in the play, but so is duty to loved ones and one’s self. The conflict between different kinds of duty provides the central tension of the play. Antony acts on duty to the state when he marries Octavia, but if he honors his heart, he has to be with Cleopatra. Friendship is also central because so much of the play is about how leaders are nothing without the people that follow them. Cleopatra constantly leans on her servants for support and advice, and Antony is undone as his own men betray him. How we view ourselves is often gauged by how others view us, and their duty to us is a reflection of our own honor.
Duty is only properly driven by loyalty in Antony and Cleopatra. Only when characters truly love their leaders do they feel beholden to stay true to them.