What evidence is there in act 5, scene 2 that Macbeth's control over Scotland and his troops is slipping?
In Act 5, Scene 2, Menteith, Caithness, Angus, and Lennox, all Scottish nobles who have defected to Malcolm's cause and are preparing to join up with the advancing English army, have a conversation which is meant to inform the audience of the current situation. The fact that these four nobles have turned against Macbeth gives visual evidence that many others are doing the same thing. Most significantly, Angus says of the besieged tyrant:
Now does he feel
His secret murders sticking on his hands.
Now minutely revolts upbraid his faith-breach.
Those he commands move only in command,
Nothing in love. Now does he feel his title
Hang loose about him, like a giant's robe
Upon a dwarfish thief.
Thus we learn in this brief scene that the English and rebellious Scottish forces are approaching Dunsinane, that revolts against Macbeth are breaking out all over the country, that those who have not revolted are not the least bit motivated to repel the invaders, and that Macbeth himself is desperate nearly to the point of madness. When Macbeth himself appears immediately after this scene, his speech and behavior confirm what these four nobles have heard about him. Since Macbeth is continually boasting about being invulnerable unless Birnam Wood comes to Dunsinane and he is confronted by a man who is not born of woman--both seeming impossibilities--these strange utterances may have given his followers the idea that he has lost his mind.