He raided through Orkney, the Hebrides and Mann (the Northern and Southern Isles), and ensured Norwegian control by a treaty with the Scottish king.

Based on Mann during his time in the west, Magnus had a number of forts and houses built on the island and probably also obtained suzerainty of Galloway.

After two unsuccessful invasions and a number of skirmishes Danish king Eric Evergood initiated peace talks among the three Scandinavian monarchs, fearing that the conflict would get out of hand.

Under unclear circumstances, while obtaining food supplies for his return to Norway, Magnus was killed in an ambush by the Ulaid the next year; territorial advances characterising his reign ended with his death.

Anders Stølen has argued that she was a daughter of Ragnvald jarl[7] (who has been identified as Rognvald Brusason, Earl of Orkney by Ola Kvalsund),[8] while historian Randi Helene Førsund has considered Tora Joansdatter more likely.

[5] Magnus grew up among the hird (royal retinue) of his father in Nidaros (modern Trondheim), de facto capital of Norway at the time.

In his youth, he was apparently more similar to his warlike grandfather, King Harald Hardrada, than to his father (who bore the byname Kyrre: "the Peaceful").

[10] Magnus's more-common byname, "Barefoot" or "Barelegs", was—according to Snorri—due to his adopting the Gaelic dress of the Irish and Scots: a short tunic, which left the lower legs bare.

[3][11] Another version (by Danish historian Saxo Grammaticus) maintains that he acquired the nickname because he was forced to flee from a Swedish attack in his bare feet,[12] while a third explains that he rode barefoot (like the Irish).

Magnus may have been present when Olaf died in Rånrike, Båhuslen (southeastern Norway) in September 1093 and was probably proclaimed king at the Borgarting,[3] the thing (assembly) of the adjacent region of Viken later that month.

Since conditions were chaotic in Norse-dominated parts of the British Isles since the death of Thorfinn the Mighty, this provided Magnus an opportunity to intervene in local power struggles.

Haakon attempted to intercept Magnus by travelling south to Viken by land (over the mountains of Dovrefjell),[23] but he died unexpectedly while hunting in February 1095.

[34] While he may have been influenced by Ingemund's murder, the Orkneyinga saga claims that Magnus was persuaded by a son of an Orkney earl, Haakon Paulsson, who wanted an earldom for himself.

[39] After his arrival, Magnus began negotiations with Scottish and Irish kings about the hird and control of land in Scotland, Ireland and the surrounding islands.

Magnus then continued to Mann, where the earl Óttar fell in a violent battle;[45] he also chased (or captured) Lagman Godredsson, King of the Isles.

During his time there, he organised Norwegian immigration to the island and had several forts and houses built (or rebuilt) using timber from Galloway on the Scottish mainland.

Appearing off the coast at Puffin Island, he interrupted a Norman victory celebration after their defeat of the Gwynedd king[49]—for the Welsh, "so opportunely it was ascribed to divine providence" according to historian Rosemary Power (although Magnus had not necessarily intended to side with them).

[54][55][56] Historian Richard Oram has claimed that references to a formal agreement with the Scottish king is a "post-Norwegian civil war confection" designed to legitimise the agenda of Haakon IV Haakonsson.

[57] Rosemary Power agrees with the Norse sources that a formal agreement with the Scots was probably concluded,[56] and Seán Duffy notes that Edgar "happily ceded" the isles to Magnus since he had "little or no authority there in any case".

[56] There may have been talks at this time of Magnus marrying Matilda, daughter of late Scottish king Malcolm III Canmore, but no marriage took place.

In Magnus's view, the border with Sweden should be set further east: at the Göta älv river, through the Vänern lake and north to the province of Värmland.

[61] In a surprise nighttime attack, Magnus assaulted Swedish forces east of Göta älv at Fuxerna (near Lilla Edet).

[63] According to Randi Helene Førsund, the Norwegians in Kållandsö appear to have been characterized by arrogance (perhaps due to their successes under Magnus) and taunted the Swedish king for taking so long to arrive.

[73] The marriage agreement described in other sources was part of the treaty;[76] Magnus's son, Sigurd, married Muirchertach's daughter Bjaðmunjo.

Magnus attempted to assert control over his disordered army, ordering part of his force to seize secure ground and use archery fire to slow the Irish.

[92] Magnus's son Sigurd returned to Norway without his child bride after his father's defeat, and direct Norwegian control in the region came to an end.

[96] About two miles (1.2 km) south of the cathedral on Horse Island is a mound which became known as Magnus's Grave after its identification on an 1859 map attributed to Danish archaeologist Jens Jacob Asmussen Worsaae.

Snorri Sturluson's description of the marshy and difficult terrain where Magnus and his men were attacked fits the conditions in and around Horse Island, making it a strong candidate for the burial site.

[98] The burial site is largely only accessible via the heritage railway in Downpatrick; a halt overlooking the barrow and runestone has been carved by James Higgins and erected by Philip Campbell,[99] local viking history enthusiast, chairman and founder of the Magnus Viking Association and the Ballydugan Medieval Settlement which is located a short distance from the Runestone on the Drumcullan Road.

[3] Near the end of Sigurd's reign (he having outlived his brothers) during the late 1120s, the previously unknown Harald Gille came to Norway from the west claiming to be a son of Magnus Barefoot and legitimate successor to the kingdom.