Yet some one must be left behind. The centre of interest had suddenly shifted, but work in plenty remained. Some one must be left in the post of peril to play Cromwell's part while he was gone; some one who knew how to strike sharp and hard, and could fix a grip of iron on the country before the army that was gathering in the Highlands could replace the one that was gone. Monk was the man, and well he justified the choice.
The force at his command consisted of but four regiments of horse and three of foot, in all less than six thousand men. With this he attacked Stirling, and on the 16th the maiden castle surrendered. For this service he received the thanks of Parliament, and was voted £500 a year in Scotch land for ever.
But the work was only commenced. By the capture of Stirling he had but secured an advanced base from which to operate against the north. The Committee of Estates, to which Charles had entrusted the kingdom before he left, was sitting at Dundee, and organising, in concert with a number of clan-chieftains, a new army for the King. Dundee then was Monk's real objective. No sooner was Stirling in his hands than he hurried forward a small flying column to stop the supplies of the town. Three or four days were spent in disposing of prisoners and booty at Stirling and in setting things in order there, for the most precise strategist of to-day could not be more careful about his base than Monk. Then the general followed with the bulk of the foot and the siege-train.
Just before reaching Dundee he was joined by a body of cavalry under two officers, who were destined to play a prominent part in history. The horse were commanded by Colonel Alured, a daring cavalry leader with red-hot political opinions of an advanced socialistic type, an Anabaptist of the Anabaptists. At the head of the dragoons rode a little fiery man, whom they all adored. It was the famous Colonel Morgan, a soldier of fortune after Monk's own heart, who knew nothing of politics and everything of his profession. They had probably served together the greater part of their lives, and were now at any rate fast friends with unbounded mutual admiration. There was no one to whom Monk would rather commit a piece of difficult work than this little dragoon, and he had arrived in the nick of time.
For Monk, as we have seen, with his advanced ideas of the military art, the Intelligence Department was his chiefest care. "The eyes of an army," to use his own expression, he cherished as his own. Spies as usual had been busy, and now he learned that on his approach the Government had retired to the Highlands and was sitting at Alyth, fourteen miles away, at the edge of the hills, where a force was daily expected to assemble for the relief of Dundee. Monk at once determined on a surprise so daring that it savours more of romance than the deliberate expedient of a wary strategist. Morgan was sent for, and he and Alured were told to take their men, disguised as far as possible and mixed with Scotch deserters, and attend the enemy's rendezvous.
Late on the night of the 27th they marched, and unmolested reached Alyth in the first hours of the morning. To avoid suspicion they boldly marched to the farther side of the town, and there quietly halted as though they were a party of the expected troops. No one interfered, and about three o'clock, after a short rest, when sleep was the deepest, they suddenly broke into the astonished town. Hardly a blow was struck. Old Leslie, the commander-in-chief, was taken in his bed, and the rest of the Government shared his fate; and as Monk went forth to direct his siege-works Alured and Morgan rode into camp with three hundred noblemen, lairds, and ministers prisoners in their train. At one stroke Scotland was as it were beheaded. It was a bloodless victory, as complete almost as the "crowning mercy" at Worcester, now on the eve of being fought. "Truly," wrote Monk in his despatch to Cromwell, "it is a very great mercy which the Lord of Hosts hath been pleased to bestow upon us, observing the time and season. This is the Lord's work, and therefore He alone ought to have the praise." But he concludes by asking for Morgan's promotion. That he could so far have departed from his ordinary style only shows us how great had been the influence of Cromwell's coercive personality upon him.
Still Dundee did not know the extent of the disaster. The garrison could not believe that all hope of relief was at an end, and contemptuously refused Monk's summons. On the third day the batteries opened. All through the last night of August they thundered, and in the morning there was a practicable breach. Monk knew well the garrison was hopelessly demoralised and would be an easy prey, yet he strove to save bloodshed. Twice again he offered them quarter, and twice again they refused. Then at last he gave the word for an assault.
The infantry were very weak from sickness, and the storming parties were strengthened by dismounted troopers and a naval brigade. These elements were not likely to decrease the heat of the fight, and added to this the town was known to contain property of immense value. With incredible fury the breach was carried in one rush. The supports of horse were through almost as soon as the footmen, and a desperate struggle ensued in the streets. In a few minutes it was over and the stormers rushed on wildly through the town hacking down everything in their way. A number of women, and even some children who were in the streets, were borne down in the rush. Soon all that resisted were a party who with the governor had taken refuge in a tower. Preparations were being made to smoke them out, when they asked and received quarter. Unhappily, as the governor was being taken before Monk he was pistolled by a fanatic officer, an outrage which the general seems to have felt as a blot on his own untarnished reputation as a soldier. Resistance was now at an end, but Monk seems to have thought it his duty to give over the town to two days' pillage as a chastisement for its obstinate refusal of quarter.
The remaining garrisons surrendered on terms in rapid succession, and the Highland strongholds were one after another reduced by his officers. He himself took no active part in the operations. The iron constitution on which he drew so recklessly during his long campaigns at length gave way, and a few days after the surrender he was laid up in Dundee with a fever. By January he had sufficiently shaken it off to be able to meet the new Scotch commissioners who had arrived at Dalkeith from London to negotiate the Union, but in February he was compelled to go south for the benefit of his health. It is worthy of note that he started on the journey in the same coach with Lambert, who was also on the commission, but before Berwick was passed they agreed to separate, ostensibly because Monk was too ill to travel fast enough for his rival.
It is said that at this time there was an idea of sending into France ten thousand of those matchless troops of whom all Europe was talking, as was afterwards done under Morgan. For Monk was reserved the superlative honour of commanding them. But the time was not yet ripe, and instead of figuring as leader of the finest soldiers in the world, for so every one then considered them, Monk went quietly down to Bath to mend his shattered health.