Singer/guitarist Jared Leto (From MusicRadar): "It's really a refrain, a segue from 'This Is War,' if you will. I guess you'd call it a mantra or a prayer. My intention is that it be uplifting, but it's probably a bit dark and nihilistic."
"The Night Chicago Died" was written and recorded by the British group Paper Lace. They talk about Al Capone in the song, but got a lot of details wrong - understandable since they wrote it based on gangster movies.