Towards the end of the Reign of David I of Scotland in the middle of the 12th century, Godred Crovan’s Celtic-Norse grandson, Somerled, married Ragnhild, daughter of Olaf of Man. The unpopular Godfred, Godred Crovan’s other grandson en son of Olaf, was deposed by some of the islands chiefs, led by his brother-in-law Somerled. After a sea battle off Islay in 1156, Somerled defeated Godred’s forces and forced a division of the Norse Kingdom of Man and the Isles. The kingdom stretched from the Isle of Man to Lewis. He became Rì Innse Gall – king or ruler of the Isles of the strangers and ruled over a wide-ranging lordship of islands and the western seaboard. While David I became occupied with English affairs, Somerled became a kind of regional governor for the Scots king.
They created a stronghold, Dunyvaig Castle, on the eastern side of Lagavulin Bay on a coastal promontory to control the coasts of Kintyre and Antrim. The site for the stronghold was on top of remains from a fortification which dates back to earlier times. By 1153 Somerled’s relation with the king of Scots became worse and in 1164 Somerled invaded the mainland and sailed up the Clyde with 160 galleys, but met his end at Renfrew. Somerled’s lands were divided amongst his three sons, Ranald, Angus and Dougall. Ranald ruled in Islay and Kintyre, adopted the title “of Islay” and called himself king of the isles and lord of Argyll. The land of Angus was later given to Donald, the son of Ranald, and to Dougall. Thus Somerled was the progenitor of both Clan Donald and Clan Dougall. Where the MacDougalls co-operated with the Scots Crown, the MacDonalds didn’t and even joined King Haakon’s 1263 expedition against Scotland. Later in 1266 the isles were held by Alexander III, King of Scots whereas the former vassals of the king of Norway were left in possession of the isles. The MacDougalls however were in favour and later kept on supporting the king of Scots whereas the MacDonalds were on the English Edward I side. But in 1306 during the civil war, the MacDougalls sided with the English in opposing Bruce which however turned out to be the loosing side and thus the Clan Donald, by supporting Bruce, came out stronger than before. Later Robert I destroyed the MacDougalls and granted much of their territory to the MacDonalds which gave them a strong position in the years to come.
The descendants of Somerled’s grandson Donald, the Clan Donald or the MacDonalds, remained in power and Islay continued to be the main seat of power in the west and became known as the home of the Lords of the Isles.
Source for this story is the book "Biography of an Island" by Margaret Storrie. This book is for sale at Amazon in association with Islayinfo.