Alexander of Islay lived from about 1390 to 1449. Also known as Alasdair MacDomhnaill or MacDhòmhnaill, he was the third chief of Clan Donald to hold the title Lord of the Isles. The wider picture in Scotland at the time is set out in our Historical Timeline.
Alexander of Islay, succeeded to the title of Lord of the Isles on the death of his father, Donald of Islay in 1423. The following year, James I returned from captivity in England and assumed the throne of Scotland. His first act was to wipe out the surviving Albany Stewarts, relatives of Robert, Duke of Albany whose death in 1420 had cleared away the main obstacle to James I's return. One effect of this was to revert to the Scottish crown the control of the Earldom of Ross, which had been claimed by Donald of Islay but controlled by Robert, Duke of Albany since the Battle of Harlaw in 1411.
James I initially held Alexander of Islay (who was a slightly removed cousin) in high regard. However, as early as 1426 Alexander had occupied much of Ross and was using the title of Master of the Earldom of Ross despite the fact that the title was now a royal possession. It is not certain whether this was with the blessing of James I or in defiance of him, though what happened next gives us a clue. In 1428 James invited Alexander to meet him in Inverness, and when he did so the King had Alexander, Alexander's mother, and many of his followers imprisoned.
James I's next move was to offer the Lordship of the Isles to John Mór MacDonald, Alexander's uncle and a man who had rebelled against Alexander's father, Donald of Islay, in 1387. John Mór refused the offer, and in a confused incident the man sent to make him the offer then killed him while trying to arrest him. James I tried to distance himself from the act, but the incident weakened his position, and before the end of 1428 he had released Alexander on the promise of good behaviour.
Alexander's "good behaviour" was to attack Inverness in Spring 1429, and to support the claims of a surviving grandson of Robert, Duke of Albany to the throne of Scotland in place of James I. The death of the rival claimant very soon afterwards left Alexander highly exposed to retribution from James I, which quickly followed. The King launched a punitive expedition in search of Alexander, who then surrendered to James in Edinburgh on 27 August 1429. Alexander was then imprisoned in Tantallon Castle in East Lothian.
In Alexander's enforced absence, James I sent Alexander Stewart, Earl of Mar, and the man who had stopped Donald of Islay at the Battle of Harlaw, to gain control of lands still owing allegiance to the Lords of the Isles. The government army faced opposition under the command of Alexander's kinsmen Donald Balloch and Alisdair Carrach, and the outcome was a costly defeat for the Earl of Mar at the Battle of Inverlochy in September 1431.
In the aftermath, James, now feeling he had no other way to bring the islands under control, released Alexander from imprisonment, though this time keeping his mother as hostage to his future good behaviour. Alexander was not to cross James again, and by the time of the latter's death in 1437, Alexander, Lord of the Isles was also using the title of Earl of Ross, apparently with the King's blessing.
In strictly territorial terms, the end of Alexander's tenure as Lord of the Isles marked the high point of the fortunes of Clan Donald. With the Hebrides, much of the west coast of Scotland and the huge expanse of Ross under his undisputed control, Alexander controlled a considerably larger area than Somerled had done at the height of his powers: though he did so with permission from the Scottish crown rather than as an sovereign monarch, independent of both Norway and Scotland, as Somerled had been.
On the other hand, by moving his focus and residence to the richer areas of Dingwall and Inverness, Alexander did much to undermine the unity and loyalty that the Lords of the Isles had once commanded across their heartlands in the west and in the islands. Alexander died in 1449. He was succeeded by his son, usually referred to as John MacDonald II, Lord of the Isles to avoid confusion with the earlier John of Islay.