Cnut, who had arrived in Denmark with a fleet in 1027, had forgiven Harthacnut his insubordination in view of his youth but had had Ulf murdered.

After driving the invaders out of Denmark and establishing his authority over Norway, he returns to England in 1028 and leaves Denmark to be ruled by Harthacnut.

Norway’s last Lade, Jarl Haakkon Eiriksson, drowns in 1029, and Cnut appoints his son Svein to rule Norway with the assistance of Ælfgifu, Cnut's first wife and Svein's mother.

Olaf makes plans to return to Norway with his army to regain his throne and the Kingdom of Norway.

Olaf, returning with an army in a bid to regain his Norwegian throne, is killed on July 29, 1030, at the Battle of Stiklestad, his forces defeated by a "Peasant Army" of rival nobles, wealthy farmers and others loyal to Cnut the Great.

King Olaf—stubborn, rash and prone to torturing and murdering those who refused to submit to Christianity—will, in an ironic twist, become Norway's patron saint.

His canonization is performed only a year after his death by the bishop of Nidaros.

The cult of Olaf will not only unify the country, it will also fulfill the conversion of the nation, something for which the king had fought so hard.

He will later be canonized and become the patron saint of Norway and Rex perpetuum Norvegiae ('the eternal king of Norway').

Cnut has installed his English concubine Aelgifu as regent, but her increasing unpopularity among the Norwegians threatens his hold on the country.

Magnus is an illegitimate son of King Olaf Haraldsson (later St. Olaf), by his English concubine Alfhild, originally a slave (thrall) of Olaf's queen Astrid Olofsdotter.

Born prematurely, the child was weak and unable to breathe for the first few minutes, and he was probably not expected to survive.

Olaf was not present at the child's birth, and his Icelandic skald Sigvatr Tordarson became his godfather.

In a hasty baptism, Sigvatr named Magnus after the greatest king he knew of, also Olaf's greatest role model, Karla Magnus, or Charlemagne.

Against the odds, Magnus had gone on to grow strong and healthy, and he had become of vital importance to Olaf as his only son.

When Olaf was dethroned by the Danish king Cnut the Great in 1028, he had gone into exile with his family and court, including the young Magnus.

They had traveled over the mountains and through Eidskog during the winter, entered Värmland, and had been given shelter by a chieftain called Sigtrygg in Närke.

After a few months, they departed Närke, and by March went eastwards towards Sigtuna, where the Swedish king Anund Jacob had left them a ship.

The party thereafter sailed through the Baltic Sea and into the Gulf of Finland, eventually landing in Kievan Rus' (Gardaríki).

They had made their first stop at Staraya Ladoga (Aldeigjuborg) to organize the further journey.

From there, they had traveled southwards to Novgorod (Holmgard), where Olaf had sought assistance from Grand Prince Yaroslav the Wise.

Yaroslav, however, had not wanted to become directly involved in the Scandinavian power-struggles, and declined to help.

After some time, in early 1030, Olaf had learned that the Earl of Lade Håkon Eiriksson, Cnut's regent in Norway, had disappeared at sea, and gathered his men to make a swift return to Norway.

Magnus was left to be fostered by Yaroslav and his wife Ingegerd.

A party including Magnus's uncle Harald Sigurdsson (later also to be king and then known as Harald Hardrada) had arrived in early 1031 to report the news of his father's death at the Battle of Stiklestad.

Magnus had for the past few year been educated in Old Russian and some Greek and has been trained as a warrior.

After Cnut's death in 1035, the Norwegian noblemen do not want to be under the oppressive rule of his son Svein and his mother Ælfgifu (known as Álfífa in Norway) any longer.

Einar Thambarskelfir and Kalf Arnesson, who had both sought to be appointed regents under Cnut after Olaf's death in 1030 (Cnut had instead appointed Svein and Ælfgifu), go together to Kievan Rus' to bring the boy back to rule as the King of Norway.

Einar Thambarskelfir and Kalf Arnesson, after receiving the approval of Ingegerd, return from Novgorod with Magnus to Sigtuna in early 1035, and receive backing from the Swedish king, brother of Magnus's stepmother Astrid.

Astrid immediately becomes an important supporter of Magnus, and an army is gathered in Sweden, headed by Einar and Kalf, to place Magnus on the Norwegian throne.

Ælfgifu and Svein have made themselves unpopular by heavy taxation and favoring Danish advisers over the Norwegian nobles, and when Magnus of Norway, the son of the former King of Norway, Olaf, invades in 1035, they are forced to flee to Harthacnut's court.

Magnus is proclaimed king in 1035, at eleven years of age; Svein dies shortly after.

Magnus at first seeks revenge against his father's enemies, but on Sigvatr's advice he stops doing so, which is why he becomes known as "good" or "noble”.

The Anglo-Saxon Chronicle reports that Harold Harefoot said that he was a son of Cnut the Great and Ælfgifu of Northampton, "although it was not true".

Florence of Worcester (twelfth century) elaborates on the subject.

Claiming that Ælfgifu wanted to have a son by the king but was unable to, she secretly adopted the newborn children of strangers and pretended to have given birth to them.

Harold was reportedly the son of a cobbler, while his brother Svein Knutsson was the illegitimate son of a priest.

She deceived Cnut into recognizing both children as his own.

Harriet O'Brien doubts that Cnut, the shrewd politician who "masterminded the bloodless takeover of Norway" could have been deceived in such a way.

She suspects that the tale started out as a popular myth, or intentional defamation presumably tailored by Emma of Normandy, the other wife of Cnut and rival to Ælfgifu.

Upon the death of Cnut on November 12, 1035, Harold's younger half-brother Harthacnut, the son of Cnut and his queen Emma of Normandy, is legitimate heir to the thrones of both the Danes and the English.

Harthacnut, however, is unable to travel to his coronation in England because his Danish kingdom is under threat of invasion by King Magnus I of Norway and King Anund Jacob of Sweden.

England's magnates favor the idea of installing Harold Harefoot temporarily as regent or joint monarch, due to the difficulty of Harthacnut's absence, and despite the opposition of Godwin, the Earl of Wessex, and the Queen, he eventually wears the crown.

There is some dispute in primary sources (the Anglo-Saxon Chronicle) about Harold's initial role.

Versions E and F mention him as regent, the others as co-ruler.

Ian Howard points out that Cnut had been survived by three sons: Svein, Harold, and Harthacnut.

The Encomium Emmae Reginae also describes Edward the Confessor and Alfred Aetheling as the sons of Canute, though the modern term would be step-sons.

Harold can claim the regency or kingship because he is the only one of the five present at England in 1035.

Harthacnut is reigning in Denmark, and Svein had joined him there following his deposition from the Norwegian throne, while Edward and Alfred are in Normandy.

Harthacnut can reign in the name of his absent brothers, with Emma rivaling him as candidate for the regency.

The Anglo-Saxon Chronicle ignores the existence of Svein, or his claim to the throne, which Howard considers as evidence of the relative entries being unreliable, of failing to give a complete picture.

The Heimskringla of Snorri Sturluson claims that Svein and Harthacnut had agreed to share the kingdom between them.

This agreement would include Denmark and (probably) England.

Snorri quotes older sources on the subject and could be preserving valuable details.

Harold reportedly seeks coronation as early as 1035.

According to the Encomium Emmae Reginae, however, Æthelnoth, Archbishop of Canterbury, refused to crown Harold Harefoot.

Coronation by the Archbishop would be a legal requirement to become a king.

Æthelnoth reportedly placed the scepter and crown on the altar of a temple, possibly that of the Canterbury Cathedral.

Offering to consecrate Harold without using any of the royal regalia would have been an empty honor.

He refused to remove the items from the altar and forbade any other bishop from doing so.

The tale goes on that Harold failed to sway Æthelnoth, as both bribes and threats proved ineffectual.

The despairing Harold reportedly rejected Christianity in protest.

He refused to attend church services while uncrowned, preoccupying himself with hunting and trivial matters.

Harthacnut is a close ally of Svein, but he does not feel his resources are great enough to launch an invasion of Norway.

The half-brothers look for help from their father, but instead they receive news of his death in November 1035.

Harthacnut succeeds his father on the throne of Denmark as Cnut III.

He is unable to come to England in view of the situation in Denmark, and it is agreed that Svein's full brother, Harold Harefoot, should act as regent, with Emma holding Wessex on Harthacnut's behalf.