Let every soldier hew him down a bough
And bear ‘t before him: thereby shall we shadow
The numbers of our host and make discovery
Err in report of us.

– William Shakespeare

Macbeth, Act 5, Scene 4. Malcolm orders his soldiers to cut down Birnam Wood tree branches and carry them in order to conceal the real size of the army about to attack Macbeth. By his trick Malcolm is unknowingly fulfilling the Witches’ prophecy that Macbeth will never be vanquished until Birnam Wood comes to Dunsinane. For as the soldiers march, it will appear as if the wood is moving to Dunsinane. This passage is foreshadowing of Macbeth’s immiment defeat.