Detailed Summary of Macbeth, Act 5, Scene 4:

Drum and colours. Enter Malcolm, Siward and Young Siward, Macduff, Menteith, Caithness, Angus, Lennox, Ross, and Soldiers, marching:
Now the Scottish forces have joined the English army. All have arrived at Birnam wood, before Macbeth's castle. Malcolm says, "Cousins, I hope the days are near at hand / That chambers will be safe," and Menteith replies, "We doubt it nothing" (5.4.1-2). Malcolm is referring to the murder of King Duncan in his bedchamber, and they are both expressing confidence that their side will win.

Malcolm gives the order for the soldiers to cut branches and carry them in order to disguise the size of the army that will attack Macbeth. However, this precaution is hardly necessary. Siward comments, "We learn no other but the confident tyrant / Keeps still in Dunsinane, and will endure / Our setting down before 't" (5.4.8-10). Siward means that it appears that Macbeth is so overconfident that he will allow the enemy to approach the castle and begin a siege, but Malcolm points out that Macbeth doesn't have much of a choice. Fighting a defensive battle is Macbeth's only option because he has hardly any support. Everyone who has had a chance to run from Macbeth has done so, and the rest don't have their hearts in the battle.

At this point, Macduff says, "Let our just censures / Attend the true event, and put we on / Industrious soldiership" (5.4.14-16). A "censure" is a judgment or opinion; "attend" means "wait for"; and "event" means "outcome." Macduff is making the point that they will know how strong Macbeth is after they have fought the battle; until that time, all they have to do is be good soldiers. Siward agrees, and thus the scene ends with a contrast between Macbeth's desperate overconfidence and his enemies' calm determination.