The bridge over the Dee had been fortified, and Montrose, remembering his former experiences at this place, led his army up the river to a ford some fifteen miles above the city. Here they crossed, and encamped for the night in the grounds of Crathes Castle, whose owner, though no King's man, thought the King's Lieutenant, with fifteen hundred men at his back, entitled to every courtesy. Next morning Montrose led his men down the north bank of the river within two miles of Aberdeen, where he found the Covenanters ready for battle. He summoned the magistrates to surrender, or at least to send the women and children to a place of safety. His summons was refused, and a drummer-boy, who had accompanied his messenger, was wantonly killed. Furious at this second and more brutal disregard of the laws of civilised warfare, Montrose promised Macdonald the sack of the rebellious town, and bade the battle begin.
As at Tippermuir the Irish held the centre; Rollo commanded on the right, Nathaniel Gordon on the left. The cavalry were on the two wings, interspersed with musketeers and bowmen. Montrose, well mounted, clad in coat and trews, with a bunch of oats in his bonnet--a _whimsy_ adopted by all his infantry--was everywhere his keen eye told him there was need of his services. The fighting was hot while it lasted, and at one moment the left flank of the Royalists was within an ace of being turned. But Montrose brought up the horse and a fresh supply of musketeers from the right wing in the nick of time, and the Covenanters having no one to take advantage of the crisis, the danger was averted. The fifty troopers performed wonders, and the Irish fought like trained soldiers. In the end good leadership and discipline prevailed over numbers, and a general charge led by Montrose in person decided the day. Within two hours after the first shot was fired the army of the Covenant was in flight. Balfour, who seems to have played no part in the battle, galloped off north across the Don with his cavalry. The foot were cut down as they ran, and the victorious Royalists burst into the town at the heels of the fugitives. Then followed a hideous scene. Montrose would not, or could not, retract the promise he had given in a moment of anger, and the wild Irish ran riot through the defenceless town. The unarmed citizens were butchered like sheep in the streets; the better sort were stripped before death, that their clothes might not be soiled with their blood; women and little children were slaughtered for bewailing their dead, and those women were happiest who expiated their tears with life. For three days the sack continued, without any interference, so far as we know, on the part of Montrose. Hitherto we have invariably seen him courteous and humane to a defeated foe, and always where it was in his power active to spare a defenceless people, and as such we shall find him hereafter. On this solitary occasion he outdoes the worst brutalities of the German wars. It was a mistake as well as a crime. It turned the scale against him in many wavering minds; and it inflamed the anger and fear of his enemies to a savage and unrelenting hatred which was destined to bear bitter fruit upon a later day. A price was now set upon his head, and Argyll openly offered a reward of £1000 to any man who should bring it in by fair means or foul.