The death of Siward, Earl of Northumberland, in 1055, opened the way still more to the ambition of Harold. Siward, besides his other merits, had added new honours to England by his successful conduct of an expedition against Scotland, where Macbeth was king. According to the well-known version of the story which Shakespeare has made immortal, Duncan, the former king, was a prince of gentle disposition, but possessed not the genius requisite for governing a country so turbulent, and so much infested by the intrigues and animosities of the great. Macbeth, a powerful nobleman, and nearly allied to the crown, not content with curbing the king's authority, carried still further his pestilent ambition. He put his sovereign to death, chased Malcolm Canmore, Duncan's son and heir, into England, and usurped the crown. It would appear, however, that the murder of Duncan is really a fiction, that he was killed while flying from a battle between the two parties, and that Macbeth, so far from being a tyrant, was really a very able and worthy ruler. Be that as it may, Siward, whose cousin was married to Duncan, undertook, by Edward's orders, the protection of this distressed family. He marched an army into Scotland; and having defeated and killed Macbeth in battle, he restored Malcolm to the throne of his ancestors. This service, added to his former connections with the royal family of Scotland, brought a great accession to the authority of Siward in the north; but as he had lost his eldest son, Osberne, in the action with Macbeth, it proved in the issue fatal to his family. His second son, Waltheof, appeared, on his father's death, too young to be entrusted with the government of Northumberland; and Harold's influence obtained that earldom for his own brother, Tostig.
There are two circumstances related of Siward which discover his high sense of honour and his martial disposition. When intelligence was brought to him of his son Osberne's death, he was inconsolable, till he heard that the wound was received in the breast, and that he had behaved with great gallantry in the action. When he found his own death approaching, he ordered his servants to clothe him in a complete suit of armour; and sitting erect on the couch, with a spear in his hand, declared that in that posture, the only one worthy of a warrior, he would patiently await the fatal moment.