It's the oldest story in the world. One day you're 17 and you're planning for someday. And then quietly, without your ever really noticing, someday is today. And then someday is yesterday. And this is your life. -One Tree Hill
The red sunlight symbolizes the mass amounts of blood spilled during the war. It is not clear what war Poe is referring too, however at the time of the writing of this poem both the war of 1812 and the wars of Spanish American independence were under way.