Hostility between the Kings of the Isles and the rulers of Ireland, and intervention by the crown of Norway (either directly or through their vassal the Earl of Orkney) were recurring themes.

The total distance from the southern tip of the Isle of Man to the Butt of Lewis, the northern extremity of the Outer Hebrides, is approximately 515 kilometres (320 mi).

The main Norse text is the Orkneyinga Saga, which should be treated with care as it was based on oral traditions and not written down by an Icelandic scribe until the early 13th century.

Scholarly interpretations of the period "have led to widely divergent reconstructions of Viking Age Scotland"[9] and Barrett (2008) has identified four competing theories, none of which he regards as proven.

This term was variously used in succeeding centuries to refer to individuals of mixed Scandinavian–Celtic descent and/or culture who became dominant in southwest Scotland, parts of northern England and the isles.

[21] According to the Orkneyinga Saga, in about 872 Harald Fairhair became king of a united Norway and many of his opponents fled to the islands of Scotland including the Hebrides of the west coast, and the Northern Isles.

Internecine fighting is recorded in the Annals of Ulster of 914, which describe Ragnall ua Ímair's defeat of Bárid mac Oitir in a naval battle off the Isle of Man.

This battle of Man, recorded by the Annals of Ulster, is said to have been won by Gofraid and "the Danes" – possibly forces directly from Scandinavia under the command of Olaf Tryggvason.

[46] The Annals of Ulster record Gofraid's death in Dalriada in 989, describing him as "king of Innse Gall" although it is not clear if this was a completely new term or had originally been used earlier, perhaps to refer to Amlaíb Cuarán's island kingdom.

[47][Note 11] The complex geography of western Scotland and the lack of written records makes certainty about the extent and nature of these kingdoms hard to fathom.

[52] Furthermore, two records in the Annals of Innisfallen hint that the Western Isles may not have been "organised into a kingdom or earldom" at this time but rather that they were "ruled by assemblies of freeholders who regularly elected lawmen to preside over their public affairs".

[59] There is also an obscure reference in The Prophecy of Berchán hinting that King Máel Coluim mac Cináeda of Scotland may have been active in Islay and Arran at about this time,[60] emphasising the potentially fluid nature of Scandinavian, Norse-Gael and Scots influence during this period.

[71][72][Note 14] It is not clear the extent to which Ui Briain dominance was now asserted in the islands north of Man, but growing Irish influence in these seas brought a rapid and decisive response from Norway.

By taking command of his ship's tiller and "sailing" across the isthmus he was able to claim the entire peninsula was an island, and it remained under Norwegian rule for more than a dozen years as a result.

[79] A second expedition in 1102 saw incursions into Ireland; the Heimskringla saga reports that he obtained Muirchertach Ua Briain's daughter Bjaðmunjo in marriage to his young son, Sigurd, whom he then left in nominal charge of the isles.

"[84] The next recorded king was Godred Crovan's son Olave Godredsson, also known as "the Red" to the Highlanders and "Bitling" to the Norwegians, the latter apparently on account of his small size.

He had spent time at the court of Henry I of England, who may have encouraged his ambitions in an attempt to minimise Ui Briain dominance over the Irish Sea and environs.

Shortly thereafter the warring Mac Lochlainn clan in Ireland along with "the fleet of Galloway, Arran, Kintyre, Man, and the territories of Scotland" are recorded fighting a naval battle off Inishowen against the Ui Briain dynasty.

[88][Note 17] Godred's dictatorial style appears to have made him very unpopular with the Islesmen, and the ensuing conflicts were the beginning of the end for Mann and the Isles as a coherent territory under the rule of a single magnate.

It is possible that Somerled first found favour with Olave by helping him wrest control of the northern Hebrides from the Earls of Orkney, whose influence had once more spread into the Sudreys.

Two years later Somerled's invasion of the Isle of Man caused Godred to flee to Norway, leaving the former as undisputed ruler of the entire realm.

[76] Somerled took this to its ultimate conclusion, declaring himself an independent ruler of the isles from his power base in the southern Hebrides and Kintyre and he had, in effect, recreated Dalriada.

[94] At this point Godred re-took possession of his pre-1158 territories and the southern isles were distributed amongst Somerled's sons as previously agreed: Dubgall received Mull, Coll, Tiree and Jura; Islay and Kintyre went to Raghnall; Bute to Aonghas, with Arran possibly divided between him and Reginald.

Diplomacy having failed to achieve much, in 1249 Alexander II took personal command of a large fleet that sailed from the Firth of Clyde and anchored off the island of Kerrera.

Following this ill-fated expedition, the Hebrides and Mann and all rights that the Norwegian crown "had of old therein" were yielded to the Kingdom of Scotland as a result of the 1266 Treaty of Perth.

It is known that the Hebrides were taxed using the Ounceland system and evidence from Bornais suggests that settlers there may have been more prosperous than families of a similar status in the Northern Isles, possibly owing to a more relaxed political regime.

[109] Rubha an Dùnain, today an uninhabited peninsula to the south of the Cuillin hills on Skye, contains the small Loch na h-Airde, which is connected to the sea by a short artificial canal.

[113] Gaelic continued to exist as a spoken language in the southern Hebrides throughout the Norse settlement period, but place-name evidence suggests it had a lowly status.

[115][116][117] In the Firth of Clyde, Norse burials have been found on Arran, although not on Bute, and place-name evidence suggests a settlement pattern that was much less well-developed than in the Hebrides.

[119][120] Initially a pagan culture, detailed information about the return of the Christian religion to the islands during the Norse-era is elusive,[121] although the modern-day Diocese of Sodor and Man retains the centuries-old name.