Macbeth is faced with a number of external conflicts in Act II of Shakespeare's Macbeth. The first one is when he encounters Banquo who challenges Macbeth in the dark of night, being unable to tell whether Macbeth is friend or foe. Once Macbeth ironically greets Banquo as "a friend," the external conflict arises as Macbeth has to dissemble and deceive Banquo when Banquo confesses to being unnerved by the witches' predictions. Even though Macbeth has continually thought about and plotted according to the witches' words, he meets the conflict by saying, "I think not of them."
The second external conflict comes when Macbeth is hallucinating while awaiting Lady Macbeth's signal--the tolling of a bell--to proceed with the plan to murder Duncan. Macbeth's external conflict is whether to let the tolling of her bell decide his fate for him. In this instance, Macbeth yields to external forces and becomes the pawn in a plan he has never really wanted.
The third set of external conflicts comes on his way to killing Duncan and in the act of killing Duncan. While on his way past the drugged guards, Macbeth hears sleepers call out “Sleep no more! Macbeth hath murdered sleep.” He also hears other awakened sleepers call out "God bless us!" and "Amen!" and finds he cannot raise his voice in a shared "Amen!" The external conflict here comes in the form of forcing himself past these disturbed sleepers and onward to the fulfillment of the plot to do murder. He triumphs over this preliminary conflict and comes to his greatest external conflict: giving the fatal physical blow to King Duncan. Macbeth, a warrior used to dealing death blows on the field of battle, summons his experience and fatally stabs Duncan thereby conquering the conflict--for better or for worse.
His next external conflict occurs when he reaches his wife's side afterward and they discover that he has been wholly unnerved and consequently brought the instrument of Duncan's death with him: he is carrying the knife that slew Duncan. This external conflict is in the form of going or not going back to the King's bedchamber to leave the knife there at the scene. Macbeth loses this conflict and Lady Macbeth returns the knife.
The final external conflict comes when the alarm is given throughout Macbeth's castle when Duncan is found and Macbeth has to act correctly. He chooses to slay the guards in a fit of feigned fury over Duncan's murder. He has success over this conflict too and pulls off a convincing display of innocent outrage at the murder of his King and friend.