In Act I, scene ii of Macbeth, the wounded sergeant describes to Duncan and Malcolm how fearlessly Macbeth fought in the battle. He says that Macbeth "carved out his passage" through the ranks of soldiers and that his sword "smoked with bloody execution." Once he reached the rebel Macdonwald, he "unseamed him from the nave to the chaps," meaning that he ripped open Macdonwald's torso from his stomach to his head, which he then, in a somewhat redundant gesture, cut off and fixed upon the battlements.

Duncan, of course, thoroughly approves of this thirst for blood, since Macbeth was fighting for him. Macbeth's manliness is therefore associated from the very beginning of the play not only with physical courage, but with extreme violence. Lady Macbeth, however, later finds both courage and capacity for violence lacking in her husband. When Macbeth protests: "I dare do all that may become a man," his wife furiously replies:

When you durst do it, then you were a man;
And, to be more than what you were, you would
Be so much more the man.

Macbeth here tries to associate the idea of manliness with honorable and civilized behavior, such as refusing to murder his king. Lady Macbeth, however, is determined that masculinity should signify only courage and violence. Eventually, Macbeth is forced to agree when he says to his wife, with grudging admiration:

Bring forth men-children only;
For thy undaunted mettle should compose
Nothing but males.

The rhetoric of Macbeth, therefore, continually associates masculinity with courage, ambition, and violence. These words, however, cannot disguise from either Macbeth or the audience the obvious fact that stabbing an old man in his sleep, while certainly violent, is hardly courageous.