Discuss the dramatic irony in Malcolm’s tactical decision in Act 5, scene 4, especially in light of the previous scene.

Malcolm is with his men in the wood of Birnam, getting ready to do battle with Macbeth. Malcolm tells every soldier to "hew down a bough and bear 't before him." This way, each man carrying a leafy tree limb, they will advance looking shadowy and hidden, and Macbeth won't be able to get a good idea of how many soldiers Malcolm has.

The dramatic irony is rich, because Macbeth, desperate and upset, has comforted himself in the prior scene by remembering the witches' prophecy that he doesn't need to fear death until "Birnam forest come to Dunsinane." Since he firmly believes the prophecy is true and knows the forest can't move, he manages to control his fears and tell himself he will triumph.

Dramatic irony is when the audience knows something that characters in the play don't. What the audience learns in scene four is that Malcolm's tactical maneuver will indeed bring Birnam forest to Macbeth. The prophecy is true, but Macbeth doesn't yet know that it will play out not for but against him. However, we, the audience, know it's over for Macbeth.