Angus Mor, the son of Donald and grandson of Ranald MacSomerled succeeded on his father's death to the lordship of Islay.
During the time when Alexander III was in his minority, Angus Mor MacDonald did not have anything to fear from him. But when Alexander reached adulthood and assumed power. He immediately resumed the ambition of his father to bring the chiefs of the west including Angus Mor, under his control. He determined to do this by whatever means necessary. He seems to have had success through diplomatic means with Angus Mor. He held Angus' son Alexander as hostage and a document was drawn that said Angus forfeited his land if he deserted the King's cause.
During this time, conflict between Scotland and Norway had become ever more likely. They were in dispute as to who had the overlordship of the Isles. The Scottish Earl of Ross, attacked the Isle of Skye, and committed many attrocities there. The Island Chiefs appealed to Haco, King of Denmark for aid. Haco heard of the attrocities against his vassals in the Northern Isles and immediately set sail. Angus Mor of Isla and Kintyre joined the Norwegian forces, as did all of the princes who descended from Somerled, except one named Ewin of Lorn.
King Haco's fleet sailed to Loch Lomond and from there entered the country of Lennox, which was on the far side of the lake, laying waste to everything in their path. Haco's expedition resulted in re-establishing Norwegian authority in the Northern Isles. There were some attempts at peace made between Alexander and Haco, but no agreement was met. The Scottish strategy was to delay. Summer was almost over and winter approaching. Haco was a long way from his home base of operation and was having difficulty supplying a force that far from home. There was to be another large battle before hostilities ceased, the battle of Largs. The battle on land left no decided victor, but the battle at sea was a loss for the Norwegians because story weather forced his fleet away from the coast and dispersed it. Scotland succeeded in acquiring the Isles by diplomatic means, and not military means. Haco died on his voyage home and the King of Scotland was forced to come to an arrangement with his son Magnus.
It took three years for these diplomatic negotiations to end. It was agreed that 4000 merks sterling would be paid to Norway, together with an annual tribute or quit-rent of 100 merks sterling, called the Annual of Norway, to be paid to the Church of Saint Magnus in Orkney. The King of Man would now be the vassal of Alexander, and both sides agreed that if the treaty was broken, they would pay a penalty of 10,000 merks to the Pope. The people who lived on the Isles were allowed to remain or to immigrate to Norway. It is likely that many of them did return to Norway.
Archibald MacDonald says that since Alexander gave such generous terms to the Isles, it is an indication that he was not sure that he could hold possession of them. Angus Mor kept his lands just as they had been before. The Sagas say that he offered to surrender his lands to Haco and that Haco in turn bestowed them back onto him. Other accounts indicate that Isla had been taken from him. Haco would not have taken Angus' lands from him by force if he had wanted his aid in the battle with Scotland. At any rate, Angus Mor appears to have faired the conflict between Scotland and Norway without any lossses. The King of Scotland seems not to have born him any ill will for having supported Haco, as he was in attendance at a convention declaring the Maiden of Norway to be the heiress of the Scottish Crown in 1284.
He seems to have been no less pious than his father and grandfather had been. He confirmed their grants to the Abbey of Saddell and granted it further lands himself by four separate charters. He made a donation to the convent of Paisley of a half a mark of silver and also gave a monastery at the same place the patronage of the Church of Kilkerran, in Kintyre.
It would be fair to say that under the feudal system Angus Mor would have been a vassal of Norway, whom he had held his lands from before Scotland and Norway made their treaty, and simultaneously a vassal to Scottland for his lands on the mainland.
Angus Mor lived part of his life at the Castle of Ardtornish. He married a daughter of Sir Colin Campbell of Glenurchy. He occupied his throne for a half a century. Hugh MacDonald of Sleat describes Angus Mor as having " a very amiable and cheerful disposition, and more witty than any could take him to be by his countenance."
They had sons Alexander, his heir and Angus Og, who succeeded when his brother Alexander died. I descend from Angus Og, so that is the point from which I will continue.
History of the Macdonalds and Lords of the Isles By Alexander Mackenzie
The clan Donald By Archibald Macdonald
Britain and Ireland, 900-1300: insular responses to medieval ... by Brendan Smith - 1999
Annals of the Reigns of Malcolm and William Kings of Scotland, A.D. 1153-1214, (Glasgow, 1910) Lawrie, Archibald Campbell
The Kingdom of the Isles: Scotland's Western Seaboard, c. 1100-1336, (Edinburgh, 1997) by Andrew R. McDonald
The wars of Scotland, 1214-1371 - Page 256
by Michael Brown - History - 2004