what does the author mean by "the fate of the nation was riding that night"?

Revere knows his task is dangerous and requires the utmost in terms of celerity, discretion, and energy. He comes across as a man impatient to carry out a mission that will save lives and push back against British tyranny, a man who will let nothing stand in his way. Longfellow meant Revere's example to inspire his contemporary readers to remain stouthearted in the face of Southern secession and imminent war. Revere's ride will affect America as a nation.