The Gesta Danorum (Books I-IX) on Iwar
The Danish History, > Book Nine.
attestation: Iwar went to England and, seeing his fleet was too weak, chose cunning over bold force
"Iwar went towards England, and when he saw that his fleet was not strong enough to join battle with the enemy, he chose to be cunning rather than bold"
attestation: Iwar tricked Ella by begging as a peace offering only as much land as an ox-hide could cover
"bold, and tried a shrewd trick on Ella, begging as a pledge of peace between them a strip of land as great as he could cover with a horse's hide."
attestation: Using the land he had cunningly acquired, Iwar built a stronghold from which to attack Ella
"together with a fleet of 1,700 ships, attacked them at Sleswik, and destroyed them in a conflict which lasted six months."
attestation: Iwar eventually captured and killed Ella, avenging Ragnar's death in the snake-pit
"appointed time; and when they had captured him, they ordered the figure of an eagle to be cut in his back, rejoicing to crush their most ruthless foe by marking him with the cruellest of birds."