La Marseillaise, if you boil it down to a single sentence, is basically "Fight on, Frenchmen... because we are utterly screwed if you don't."--almost all of the violence in the song is about the violence directed towards the French by the various coalitions arrayed against it at that time. (Also extremely notable for a national anthem of that period, it never specifically identifies an enemy--contrast that to the dueling German anthem in the film, which is a rather explicitly anti-French anthem.)