As they approach the castle, Malcolm and his army come to a wooded area known as Birnan Wood. In order to camouflage their numbers and surprise Macbeth, Malcolm tells his soldiers to cut branches from the trees and to use them to shield themselves.
The significance of Malcolm's Act 5.4 approach to the Dunsinane Castle with tree branches is the ultimate demise of Macbeth, who believed he was invincible since the weird sisters had told him he could never be overthrown until "Great Birnan wood to high Dunsinane hill/Shall Come". However, the sisters seemed to have referred only to the branches of the trees of Great Birnan coming to Dunsinane hill.