What is the theme of "Paul Revere's Ride"?

If a theme can be expressed in a single word, then the appropriate word for Longfellow's iconic American poem is "patriotism." Longfellow's speaker relates a story of an American patriot of the Revolution, Paul Revere, waiting for a signal as to the anticipated movements of British troops and sailors massed in and around Boston in April of 1775. After Revere receives the "intel," he sets out on a breakneck ride through the countryside surrounding Boston to spread the word to his fellow patriots as a call to arms. Though Longfellow's poem very loosely plays with the facts of that evening, the spirit of the poem captures the cooperation, diligence, courage, and determination of the men who dedicated their lives to the cause of liberty.
Longfellow's speaker invokes the attention of "children" in the first stanza to inform them that he will tell the story of Paul Revere's exploits since "hardly a man is now alive/who remembers that famous day and year." The speaker clearly wants to preserve the legend of this hero of the Revolutionary War for succeeding generations.
https://poets.org/poem/paul-reveres-ride