The narrator says that it is difficult not to digress in telling the story and he hopes the reader will follow him along this "bypath" from the main route of the narrative. He says that recent inventions have changed sea warfare, just as the introduction of gunpowder changed warfare on land. But, he insists, there is still a kind of "displayed gallantry" that is important regardless of military technology.
The narrator draws attention to his own digression from the main narrative, making sure the reader is aware of his role in constructing the story. Modern military technology changes the nature of combat, but the narrator still thinks there is a place for the performance, in show if not in fact, of old-fashioned bravery in modern combat.
The narrator describes Admiral Nelson's naval battle at Trafalgar, where he died in victory, contrasting it to the combat of ironsides nowadays. Before entering battle, Nelson wrote his will and dressed in all his medals and military honors. The narrator compares Nelson's glorious behavior to that of heroes from "the great epics and dramas."
The narrator idolizes Admiral Nelson and the glorious military past that he represents, and from which the present era has declined.