The consolidation of the kingdom of Dál Riata around the 4th century, linking the ancient province of Ulster in the north of Ireland and western Scotland, accelerated the expansion of Gaelic, as did the success of the Gaelic-speaking church establishment. Irish Placename evidence shows that Gaelic was spoken in the Rhinns of Galloway by the 5th or 6th century.
Starting sometime around the 5th century Gaelic language and culture spread from Ireland to the southwest coast of Scotland where it may have already existed since Roman times. Uncertainty over this comes as a result of the fact that there is disputed archaeological evidence to support the generally accepted tale of migration while there is some to suggest that there was none - the evidence also points to the population of the area (modern day Argyll) being constant during the time of the alleged Scottish invasion. This area was known as Dál Riata.
The Gaels soon spread out to most of the rest of the Scotland country. Gaelic has been spoken in what is now Scotland; it has lately been proposed that it was spoken in Argyll before the Roman period, but no consensus has been reached on this question. In 575 Columba revisted Ireland (Bangor) with King Aidan of Dalriada to hold a national convention at Drumceatt (Mullagh) near Londonderry attributed separately from the Tara kings.
In the Gaelic language, offspring of the race of Diarmid are called Siol Diarmid -Inishowen. The territory comprised part of the Eugenian counties of Tipperary and Limerick, now the baronies of Owney and Owneybeg
Ninian's church in the Orkneys and Shetland, established in the early part of the 5th century, received its first attacks from Norse pirates sometime in the 6th century, and was also attacked by Aidan, king of the Dalriadans, the aforementioned Gaels who colonised the west coast of Scotland. Following the foundation of Lindisfarne in 635 by Saint Aidan, Hiberno-Scottish missionaries converted most of Anglo-Saxon England during the following decades, the last pagan Anglo-Saxons king, Penda of Mercia died in 655.
History suggests that Pictish survivors escaped south to the east coast of Caithness and Sutherland and to the Hebrides. What we do know is that there was a considerable Pictish settlement in the north of Skye evidenced by the finding of three of the earliest class I Pictish stones at Clachard Tote, Dunvegan and Fiskavaig. The Romans referred to Scotland as Caledonia, a name derived from the Pictish tribe Caledonii, which fought Agricola at Mons Graupius in 84 AD. Roman accounts of the Pictish Wars as well as later accounts, it appears that the Pictish lands were essentially north of the Forth-Clyde line, north of the Antonine Wall.
In the Irish Annals of Tighernac and Ulster, under the date of 668, note is made of the voyage of the sons of Gartnait with the Columban clergy of Skye to Ireland, and their return two years later. These entries frequently refer to events which can be dated to some years earlier. There are historical Pictish kings of the name Gartnait and this particular entry refers to one who is recorded as being active in battle in 649. Mention is also made of Cano from Skye, son of Gartnait, engaged in strife with the descendants of Aidan, the Dalriadan king, who has already been mentioned in warfare in the northern isles. It is evident that these were attempts by the Dalriadans to impose on the ruling Pictish families an overlordship which in Skye was unsuccessful, indicating a powertul Pictish presence in the island.
The date 668 of the entries in the Ulster annals are thought to have been copied from similar recordings made in Iona some years earlier and now lost, referring perhaps to the yeare 664, the date of the famous Synod of Whitby, when the Roman method of calculating Easter was chosen in preference to that of the Irish. We know that there was a strong Columban contingent present there to support the defeated Bishop Colman of Lindisfarne, and that following the Synod he resigned and left for Ireland, accompanied by Columban clergy who helped him build a monastery on Inisbofin (Island of the White Cow). It is intriguing to think that his company may have included the sons of Gartnait and their followers, but of this we have no definite record.
Skye, by the end of the sixth century was an island divided, with a mainly Gaelic presence in the South end consisting of the original Celtic stock from Ireland, and an influx of the ambitious Dalriadan Gaels, while in the North the Picts had become the predominant force. Columba was of Gaelic stock but also had Pictish blood and was fostered by Cruithnechan, an Irish Pict. His mentor Finnian of Clonard, whose school numbered 3,000 students, chose Columba as the most suitable man for this daunting task. Both Viking and Scot formed one people under a single lord and came to share a single culture, one way of life - they were to become a powerful and noted race known as the Gall-Gaidheal, literally meaning 'Foreign-Gaels'. It was upon the seas their power was situated under the rule of the kings of the isles yet new enemies arose in the East. The Stewarts made inroads in the west coast and eventually Somerled assembled a sizeable army to repel them. He advanced to the centre of the Stewarts own territory, to Renfrew, where a great battle was fought in 1164.
