Battle of Holmengrå The Battle of Holmengrå ( Norwegian : " Slaget ved Holmengrå " ) was a naval battle fought on 12 November 1139 near the island Holmengrå south of Hvaler , between the forces of the child kings Sigurd Haraldsson and Inge Haraldsson on the one side , and on the other side the pretender Sigurd Slembe and his ally King Magnus the Blind ( by Sigurd ' s claim his nephew ) . Inge and Sigurd Haraldsson were sons of the previous king Harald Gille , who had been killed by Sigurd Slembe in 1136 . The sons of Harald Gille emerged victorious from the battle . Magnus the Blind was killed in action , while Sigurd Slembe was betrayed , captured , and later tortured and executed . Background . After Sigurd Slembe reportedly was told by his mother that he was a son of King Magnus Barefoot , he travelled to Scotland where he gained military experience , and went on a pilgrimage to the Holy Land . Sigurd returned to Norway in 1136 and arranged a meeting with King Harald Gille , requesting to be recognised as his brother ( Harald had also claimed to be a son of Magnus Barefoot ) , but instead found himself accused of a murder in Orkney and outlawed by Harald . Sigurd managed to escape , and after some time in hiding , he and some supporters assassinated Harald in Bergen . While Sigurd took responsibility for the murder , the people responded that they did not want a man who murdered his brother for a king , or alternatively , if he was not Harald ' s brother , that he had no right to the throne . After Harald ' s death , his queen Ingrid Ragnvaldsdotter and the chieftains quickly arranged to have Harald ' s sons , still children , proclaimed as kings . Sigurd Haraldsson was proclaimed king at the Øyrating in Trøndelag , while Inge Haraldsson was proclaimed king at the Borgarting in the south - east . Since they had been brought up in different parts of the country , both were proclaimed kings by their respective supporters , but the two factions soon joined forces in light of the threat from Sigurd Slembe . Sigurd Slembe was again outlawed , and in an attempt to increase his support he allied himself with Magnus the Blind , who had been deposed by Harald Gille in 1135 , and had him reinstated as king . When he was deposed , Magnus was blinded , castrated , and had one of his feet cut off , after which he had been placed in a monastery . Following his release by Sigurd , he managed to raise an army in the Uplands by himself , but he was defeated by Harald ' s sons in the Battle of Minne and fled to Denmark . Sigurd also went to Denmark with a small army , and thereafter turned towards raiding the Norwegian coast . Although Sigurd won little support , he gained much loot from the raids , which after a while allowed him to purchase troops in Denmark . The battle . The fleet of Sigurd Slembe and Magnus the Blind finally met the fleet of the child kings Sigurd and Inge Haraldsson on 12 November 1139 , near the island Holmengrå south of Hvaler . After the first clash , Sigurd Slembe ' s contingent from Denmark retreated with their 18 ships , out of Sigurd ' s fleet of a total 30 ships . The casualties in the battle were heavy . Magnus was struck by a spear and killed along with one of his men , Hreidar Griotgardson , who had attempted to carry the king to safety over to another ship . Sigurd Slembe attempted to escape by jumping in the water and hiding under his shield , but he was captured after being betrayed by one of his men , who told his enemies where Sigurd was in exchange for being spared his life . Sigurd Slembe was executed after the battle following brutal torture and mutilation . Although the chiefs had wanted to execute Sigurd instantly , according to Snorri Sturluson , " the men who were the most cruel , and thought they had injuries to avenge , advised torturing him . " Sigurd ' s arms and calves were crushed with axe - hammers , the skin on his head was cleaved , his back was flayed and flogged , and his spine was broken , after which he was hanged , decapitated and thrown into a scree of rocks .