Possibly it was this staunch attitude of Anund Jacob which discouraged Knut from waging open war against Olaf. At all events he went (1026) as a pilgrim to Rome, not as conqueror to Norway. In the meanwhile, his brother-in-law, Earl Ulf,[A] headed a rebellion against him in Denmark, and entered into an alliance with Olaf Haroldsson and Anund Jacob. Both thought this a convenient opportunity for striking a blow at the threatening power of Knut, and gathered a fleet with which they ravaged the coasts of Halland and Skaane. They even in some places summoned the people to the thing and received their homage. These tidings reached Knut who promptly returned from his pilgrimage, and came within a hair of capturing the two kings who did not suspect that he was near. Knut's ships were so greatly superior both in size, number, and equipment, that it would have been folly to remain and await battle. Olaf and Anund, therefore, hastened along the coast of Skaane toward Swedish territory, hotly pursued by Knut. They put up in the Helge-aa, a short river, uniting a series of lakes, near what was then the boundary between Sweden and Denmark. Olaf made haste to dam up the river where it issued from the lake, and filled the river-bed with a mass of trees and other obstructions. Late in the afternoon Knut sailed into the harbor, and found it deserted. The allies lay with their fleet outside the harbor, apparently ready for battle. It was, however, too late in the day to begin the fight, and Knut left part of his fleet outside to watch them. In the night the command was given to break the dam, and an enormous volume of water rushed down upon the Danish and English fleet, which broke from its moorings, and drifted seaward in disorder. A considerable number of people were drowned, but the ships though much damaged were not wrecked. The confusion was, on the whole, less than had been anticipated, and Earl Ulf, seeing that there was a chance that Knut might save himself, turned traitor once more and went to his rescue. The Swedes and the Norsemen, perceiving that the Danish king with this accession of strength was too formidable, sailed away without making an attack (1027). Knut, instead of pursuing them further, sailed back to England, but in the following year returned with a greatly increased force. He had by his extensive system of bribes effectually secured the friendship of the disaffected Norse chiefs, and therefore steered without hesitation to Nidaros where he was proclaimed king of Norway. He appointed his nephew Earl Haakon, the son of Earl Erik, regent in his absence.

[A] Ulf Jarl, the ancestor of a long line of Danish kings, was the grandson of Thyra, the sister of Sweyn Forkbeard, by her first husband the Swedish Prince Styrbjörn. He was, accordingly, through his grandmother, a descendant of Gorm the Old, and of Ragnar Lodbrok.

For Olaf there was now really nothing to do but to leave the country. He determined, however, to make a last effort to maintain himself and sailed with a few ships, and as many men as remained faithful to him, up along the coast, hoping that he might yet be able to rally a sufficient force to expel Earl Haakon. When Erling Skjalgsson heard of his approach, he called together his household troops, and manned his fleet. The king, however, who had no desire to fight with Erling, had already slipped by, but was no further in advance than that he could easily be overtaken. Erling, accordingly, started in pursuit, but allowed himself by a stratagem to be separated from his main force, and after a heroic fight lost all his men and was captured by Olaf. As he stood alone among a heap of the slain, his gray locks falling down over his shoulders, the king called to him:

"Thou settest thy face straight against us to-day, Erling." "Face to face do eagles fight," answered Erling; "wilt thou give me peace?"

Olaf, after some deliberation, declared that he would; but on second thought half repented of his generosity. He took his axe and gently scratched the old man's cheek, saying: "Something must be done to mark the traitor to his king."

One of the king's men who stood by suddenly raised his axe and cleft Erling's skull, saying:

"This is the way to mark a traitor to his king."

Thus died the mightiest chieftain in all Norway. No representative of the tribal aristocracy, before or since, ever possessed such power as Erling Skjalgsson.

Olaf continued his voyage northward to Söndmöre where a great number of his followers left him, while at the news of Erling's death enemies blocked his way wherever he turned. He saw that his last hope was gone; and with a few friends fled through Valdalen across the mountains into Sweden, where he left his wife and daughter. Thence he travelled to Russia (1029), where he was warmly welcomed by his brother-in-law, King Jaroslav, who had married Ingegerd, the sister of Anund Jacob.

Norway was now a province of a foreign power. The separatistic tendencies of the old tribal magnates had triumphed over the national idea represented by King Olaf. It was they and not King Knut who, in order to gratify their own greed for power, had destroyed the national unity. In order to secure their own independence, each in his own shire, they sacrificed the national independence. It was natural that Knut, who based his dominion upon their support, should make them large concessions. He flattered Einar Thambarskelver, hinting that if Earl Haakon had not been his nephew he would have made Einar regent of Norway. Kalf Arnesson, the mightiest chief among the In-Trönders, he called over to England and assured him, too, that he was the man for the earl's place. For Earl Haakon, he said, was too conscientious to break his oath to Olaf Haroldsson, in case the latter should return and attempt to regain his kingdom. It may have been true that he vaguely distrusted the earl; for on a slight pretext he summoned him to England and sent him on an expedition, the nature of which is not entirely clear. From this expedition, however, Earl Haakon never returned, and it was reported that he had been drowned at sea with all his men. Björn Stallare, Olaf's friend, hastened to Russia with this intelligence, and found his old master at King Jaroslav's court. Olaf asked him for tidings of home, and how his friends had kept their oath of allegiance.