The MacDonnels descended from the twelfth-century Scottish warlord Somerled and from Alexander MacDonald, 5th of Dunnyveg, a Scottish-Irish magnate, who was driven out of Scotland by James IV and fled to Ulster where the family was already established through a series of marriages.

He appears below as the elder of two brothers: On 28 May 1618 Randal's father was created Viscount Dunluce[20] and in 1620 1st Earl of Antrim by King James I of England.

In 1635 he began a career as a military contractor by agreeing to raise two regiments of Irish troops for service in the French army, but the plan was vetoed by the King.

In 1635 he married Katherine Manners, the widow of George Villiers, 1st Duke of Buckingham,[25] who had been England's Chief Minister under both James I and Charles before his assassination in 1628.

[33] Along with the family's traditional Scottish followers in the Western Isles, Antrim's tenants provided him with an important power base during the coming wars.

[c] Charles' attempts to impose religious reforms on the Church of Scotland led to the signing of the National Covenant in 1638, and the outbreak of the Bishops' Wars in 1639.

Antrim saw an opportunity both to assist the king, and also regain traditional MacDonald lands in Scotland from Archibald Campbell, 1st Marquess of Argyll, a leader of the Covenanters.

For the Irish government, the project would also prevent the Covenanters invading northern Ireland, where they enjoyed strong support amongst the Presbyterian settlers, many of whom were Scots emigrants.

Wentworth's refusal was likely due to his own plans for the regular Irish Army to launch a rival invasion from Ireland against Dumbarton and his mistrust of the Earl's motives.

In response, Argyll raised troops of his own in Scotland and attacked the MacDonalds who were arming in anticipation of Antrim's invasion, driving many into exile in Ireland.

[39] Based in Carrickfergus, Antrim began raising his army in December 1638 although it wasn't until April the following year that he formally received a commission from the King authorising him to do so.

Antrim recruited his army from many of the leading Gaelic families of Ulster, but Wentworth blocked a plan to import experienced Irish mercenary officers from Europe to command them.

The future of the New Irish Army became a source of controversy once the Scottish crisis ended, as it was alleged that Charles I intended to ship them to England to enforce his will against the London Parliament with whom he was in dispute.

He later claimed he was contacted by a messenger named Thomas Bourke, on the King's behalf, and encouraged to stop the New Irish Army from disbanding, to raise its strength to 20,000 and to equip it for operations in England.

Although Sir Phelim O'Neill announced in the Proclamation of Dungannon that he had a commission from the King that authorized the rebellion, Antrim remained broadly neutral.

He assisted the besieged Protestant garrison during the Siege of Coleraine, persuading his Catholic tenants to abandon the campaign and sending supplies of food to the hard-pressed inhabitants.

He returned to Oxford in December with a scheme for raising 10,000 Irish for service in England and 2000 to join Montrose in Scotland, which through the influence of the duchess of Buckingham secured the consent of the king.

[46] He returned to Kilkenny in February, took the Irish Confederate oath of association, and was made a member of the council and lieutenant-general of the forces of the Catholic confederacy.

The confederacy, however, giving him no support in his projects, he threw up his commission, and with Ormond's help despatched about 1600 men under his kinsman Alasdair MacColla in June to Montrose's assistance in Scotland, sparking a Scottish civil war.

He visited Cork and afterwards in July 1646 joined his troops in Scotland, with the hope of expelling Argyll from Kintyre; but he was obliged to retire by order of the king, and returning to Ireland threw himself into the intrigues between the various factions.

Late in 1647 he was appointed with Muskerry and Geoffrey Browne by the Irish confederacy to negotiate a treaty with the Prince of Wales in France, and though he outmanoeuvred his companions by starting a week before them, he failed to secure the coveted lord-lieutenancy, which was confirmed to Ormond.

He was investigated by the new Royalist authorities for several offences, particularly allegations that he had taken part in the 1641 Irish Rebellion and that he had publicly suggested Charles I had secret involvement with the rising.

Subsequently, being called before the lords justice in Ireland, In 1663 he succeeded, despite Ormond's opposition, in securing a decree of innocence from the commissioners of claims.

This raised an outcry from the adventurers who had been put in possession of his lands, and who procured a fresh trial; but Antrim appealed to the king, and through the influence of the queen mother obtained a pardon, his estates being restored to him by the Irish Act of Explanation in 1665[52][53] Antrim was described by Clarendon as "of handsome appearance but of excessive pride and vanity and of a marvellous weak and narrow understanding".

He married secondly Rose, daughter of Sir Henry O'Neill, but had no children, being succeeded in the earldom by his brother Alexander, 3rd Earl of Antrim.