Twelve of the tax-gatherers who ventured to disobey his command, were captured and hanged. Such an insult the Swedish king could not allow to pass unavenged, and Olaf made preparations to receive him. He built a rude fortress on a headland projecting into the river Glommen, near the cataract Sarpen. In connection with these fortifications he founded a city called Borg or Sarpsborg, built a "king's hall," and offered protection to traders who came to settle there. The expected invasion from Sweden would naturally be directed through this district, and the site of the new city was therefore chosen chiefly for its strategic value. For a while, however, no decisive action was taken by the king of Sweden, who contented himself with killing Olaf's tax-gatherers in Jemteland in retaliation. The fact was that the feud was purely a personal one between the two kings, while their subjects, having no grudge against each other, desired peace. The king's friend and marshal, Björn Stallare, was induced to speak in the people's cause, and was finally commissioned to go as Olaf's embassador to Sweden, proposing peace on the conditions already named. But this embassy involved great danger, as Olaf the Swede, in his fury, did not even permit the name of his enemy to be mentioned in his presence. Björn therefore sent his friend, the Icelander, Hjalte Skeggesson, in advance to prepare the way for him, while he himself tarried with Ragnvald, the earl of Vestergötland, who had married the sister of Olaf Tryggvesson. Ragnvald's foster-father was the mighty peasant, Thorgny Thorgnysson, the law-man.[A] By securing the friendship of the earl, Björn accordingly assured himself of protection, in case the king should attempt violence against him. At the great winter _thing_ in Upsala, where the king was present, he suddenly rose out of the throng of the people and said in a loud voice; so that all could hear him: "King Olaf sends me hither to offer the king of Sweden peace and the boundary which from ancient times has been between Norway and Sweden." [Footnote A: _Laga-madr_ is not a lawyer in the modern sense, but rather a kind of judge. The office had a slightly different significance in Sweden from what it acquired in Norway when introduced there by King Sverre.]