When King Olaf and King Onund heard that King Canute was come from the West, and also that he had a vast force, they sailed east to Scania, and allowed themselves to ravage and burn in the districts there, and then proceeded eastward along the land to the frontier of Sweden. As soon as the country people heard that King Canute was come from the West, no one thought of going into the service of the two kings.
Now the kings sailed eastward along the coast, and brought up in a river called Helga, and remained there some time. When they heard that King Canute was coming eastward with his forces against them, they held a council; and the result was, that King Olaf with his people went up the country to the forest, and to the lake out of which the river Helga flows. There at the riverhead they made a dam of timber and turf, and dammed in the lake. They also dug a deep ditch, through which they led several waters, so that the lake waxed very high.
In the river-bed they laid large logs of timber. They were many days about this work, and King Olaf had the management of this piece of artifice; but King Onund had only to command the fleet and army. When King Canute heard of the proceedings of the two kings, and of the damage they had done to his dominions, he sailed right against them to where they lay in Helga river. He had a War-force which was one half greater than that of both the kings together.
Sigvat speaks of these things: —
"The king, who shields
His Jutland fields
From scaith or harm
By foeman's arm,
Will not allow
Wild plundering now:
'The greatest he,
On land or sea.'"