Duncan the sick, who Shakespeare famously offed through the ill-work of Macbeth, died on August 14, 1040. It was in reality Macbeth, or his men, who killed Duncan, after Duncan took an army into Macbeth's home territory of Moray.
Sir Walter Scott wrote of Duncan and Macbeth in his "History of "Scotland":
"Duncan, by his mother Beatrice a grandson of Malcolm II, succeeded to the throne on his grandfather's death, in 1033: he reigned only six years. Macbeth, his near relation, also a grandchild of Malcolm II, though by the mother's side, was stirred up by ambition to contest the throne with the possessor. The Lady of Macbeth also, whose real name was Graoch, had deadly injuries to avenge on the reigning prince. She was the granddaughter of Kenneth IV, killed 1003, fighting against Malcolm II, and other causes for revenge animated the mind of her who has been since painted as the sternest of women. The old annalists add some instigations of a supernatural kind to the influence of a vindictive woman over an ambitious husband. Three women, of more than human stature and beauty, appeared to Macbeth in a dream or vision, and hailed him successively by the titles of Thane of Cromarty, Thane of Moray, which the king afterwards bestowed on him, and finally by that of King of Scots; this dream, it is said, inspired him with the seductive hopes so well expressed in the drama.
"Macbeth broke no law of hospitality in his attempt on Duncan's life. He attacked and slew the king at a place called Bothgowan, or the Smith's House, near Elgin, in 1039, and not, as has been supposed, in his own castle of Inverness. The act was bloody, as was the complexion of the times; but, in very truth, the claim of Macbeth to the throne, according to the rule of Scottish succession, was better than that of Duncan. As a king, the tyrant so much exclaimed against was, in reality, a firm, just, and equitable prince. Apprehensions of danger from a party which Malcolm, the eldest son of the slaughtered Duncan, had set on foot in Northumberland, and still maintained in Scotland, seem, in process of time, to have soured the temper of Macbeth, and rendered him formidable to his nobility. Against Macduff, in particular, the powerful Maormor of Fife, he had uttered some threats which occasioned that chief to fly from the court of Scotland. Urged by this new counsellor, Siward, the Danish Earl of Northumberland, invaded Scotland in the year 1054, displaying his banner in behalf of the banished Malcolm. Macbeth engaged the foe in the neighbourhood of his celebrated castle of Dunsinane. He was defeated, but escaped from the battle, and was slain at Lumphanan in 1056."