How does Shaw employ irony in the opening lines of the play?

Shaw opens the play with a line from Virgil's epic "The Aeneid." In this line, "Of arms and the man I sing...," Virgil is opening glorifying the act of war and those who perform the heroic feats of epic tales. Shaw, on the other hand, employs irony in the use of this text, as his sole purpose in the play is to condemn all romantic notions of war.