Unification of Scotland

In the 10th century the Alban kings, having repulsed the Vikings, repeatedly attacked the Northumbrian strongholds south of the Firth of Clyde. All these attacks ended in failure. During the reign (1005-34) of Malcolm II Mackenneth, the Northumbrians were decisively defeated in the Battle of Carham (1018). With this event and as a result of the inheritance of the crown of Strathclyde by Malcolm's grandson and successor, Duncan I, the Scottish domains, thereafter known as Scotland, embraced all the territory north of Solway Firth and the Tweed River.
Unlike the "King Duncan" of Shakespeare's Macbeth, the historical Donnchad appears to have been a young man. He followed his grandfather Máel Coluim as king after the latter's death on 25 November 1034, without apparent opposition. He may have been Máel Coluim's acknowledged successor or tánaise as the succession appears to have been uneventful. Earlier histories, following John of Fordun, supposed that Donnchad had been king of Strathclyde in his grandfather's lifetime, ruling the former Kingdom of Strathclyde as an appanage. Modern historians discount this idea.
Another claim by Fordun, that Donnchad married a sister of Earl Siward of Northumbria, appears to be equally unreliable. An earlier source, a variant of the Chronicle of the Kings of Alba (CK-I), gives Donnchad's wife the Gaelic name Suthen. Whatever his wife's name may have been, Donnchad had at least two sons. The eldest, Máel Coluim mac Donnchada was king from 1057 to 1093, the second Domnall Bán was king afterwards. Máel Muire of Atholl is a possible third son of Donnchad, although this is uncertain.The early period of Donnchad's reign was apparently uneventful, perhaps a consequence of his youth. Mac Bethad mac Findláich is recorded as his dux, literally duke, but in the context — "dukes of Francia" had lately replaced Carolingian kings of the Franks and the over-mighty Godwin of Wessex was called a dux — this suggests that Mac Bethad was the power behind the throne.

Duncan's reign, a period of disastrous wars and internal strife, was ended in 1040 with his assassination by Macbeth, mormaor (great steward) of Ross and Moray, who then became king of Scotland. Macbeth, according to history a successful king, held the throne until 1057, when he was defeated and killed by Duncan's son Malcolm Canmore.