Hepburn's regiment in France. He came home to join the army of the covenant, and as major under Montrose distinguished himself by storming the Brig of Dee in June 1639. He afterwards entered the parliamentary army in England, and was conspicuous for his bravery and generosity. He was made lieutenant-general, but resigned his commission when the army was remodelled, and rejoined that of his countrymen. He was second in command at the battle of Philiphaugh in September 1645, when he contributed so much to the victory that the estates gave him twenty-five thousand merks. The following year he pursued Montrose in the north, burnt his castle of Kincardine, and shot twelve of the garrison who had surrendered. When the king ordered Montrose to disband his forces, Middleton was employed by the estates to negotiate conditions. In July 1646 the two commanders had a long conference in a meadow near the river Islay in Angus, when Middleton granted Montrose and his followers more favourable terms than the commission of assembly approved of.
In 1647 he repressed a royalist rising in the north under Huntly. In 1648 he was appointed lieutenant-general of the cavalry in the army raised by the Scottish estates to rescue the king from the hands of the sectaries, and on his march south he received a wound at Mauchline-Muir in dispersing some two thousand ultra-covenanters, who had assembled in arms on the Monday, after a communion, to resist the action of the government in connection with ‘the engagement.’ Middleton behaved with great bravery at the battle of Preston, but his horse having been shot under him he was taken prisoner and confined at Newcastle. He was afterwards allowed to reside in Berwick, when, as some say, he broke his parole and returned to Scotland. Up till the revolution in the end of 1648 he had been a zealous covenanter, but after that time his ardour cooled. In 1649 he unsuccessfully attempted a rising for Charles II in the highlands, and was allowed to return home on ‘giving assurance of his dutiful carriage in time coming.’ The general assembly of that year threatened him with excommunication, but having appeared before it and pleaded his own cause, he got leave to sign ‘the declaration and acknowledgment’ prescribed to those who had taken part in ‘the engagement’ or ‘in the late rebellion in the north.’ In 1650 Middleton joined the king on his landing in Scotland, but some months later he and others, resenting the treatment which his majesty received from the government, raised a separate force in the north in his interest. Leslie marched against him, and as Charles urged him to submit, and the estates offered an indemnity, Middleton agreed to terms on the basis of the covenants. The commission of the church, however, was not satisfied, and on a motion made by James Guthrie, minister of Stirling, and carried by votes of elders, resolved on his excommunication. This was opposed by many of the leading ministers, and the committee of estates urged delay; but Guthrie carried out the sentence on the following Sunday. At its next meeting the commission resolved to undo what had been done so rashly, and Middleton, having done penance in sackcloth in the church of Dundee, 12 Jan. 1651, was restored to church communion. After this he took a prominent part in the conflict with Cromwell till the battle of Worcester, when he commanded the cavalry. On that disastrous field, after driving back the enemy, he was wounded, taken prisoner, and sent to the Tower of London. Cromwell wished to have him tried for his life, but he escaped in his wife's clothes and joined the king at Paris.
He was appointed captain-general of the forces that rose for the king in the highlands in the end of 1653, and took command at Dornoch early in 1654. Monck marched against him with a large force, and in July came upon him by surprise near Lochgarry, when his followers were dispersed, and he escaped with difficulty and joined the king at Cologne. Cromwell exempted him from the act of indemnity, and he remained abroad till the Restoration, with the king, or employed by him on missions to various courts. In 1656 Charles had made him an earl. In 1660 he returned to England in the same ship with the king. His peerage was then confirmed by letters patent under the title of Earl of Middleton, Lord Clermont and Fettercairn. He was also appointed commander-in-chief in Scotland, governor of Edinburgh Castle, and lord high commissioner to the Scottish parliament. He arrived at Holyrood in the end of December, having been escorted from Musselburgh by many of the nobles and gentry and a thousand horse.
In January 1661 he opened the Scottish parliament with great state, and soon after passed the acts rescissory, which annulled all the legislation of the previous twenty-three years. In May following he presided at the funeral of Montrose, whose scattered limbs were then collected and buried with all honour in St. Giles's, Edinburgh. He took an active part in the prosecution of Argyll, who was executed on the 27th of the same month, and he is said to have cherished a personal animosity against James Guthrie [q. v.],
