James Graham, 5th Earl of Montrose, had signed the National Covenant in 1638, along with most of his countrymen and indeed, had fought for it's principles against the king, Charles I, in the short campaigns of 1639-40. By these actions the aims of the Covenant had been achieved, but Montrose and his friends came to realise that the Covenanting hierarchy in Scotland, headed by the Marquis of Argyll, chief of the powerful Clan Campbell, were aiming at much greater power and to overthrow the king.

Montrose attempted to warn his sovereign, but Charles would not listen and it was not until the solemn league and the Covenant had been agreed between the Scottish government and the English parliament, that the king finally realised the danger.

It was almost too late, as the Scots had assembled a sizeable army under General Alexander Leslie (later the Earl of Leven) and sent it south to join the parliamentary forces operating against the King in the North of England. This so upset the balance of power in that area, that the King's general, Prince Rupert, lost the Battle of Marston Moor, on 2nd July, 1644.

Montrose was already at Oxford, the King's headquarters, where he had been commission as the Royal Lieutenant-General in Scotland and raised to the rank of Marquis. He and two companions crossed the border in disguise. posing as Leslie's troopers returning home on leave and, in Perthshire, near Blair, met a force of about 1,500 exiled MacDonalds from Ireland, sent over by the Earl of Antrim to aid his endeavour. He found the Irishmen, under their leader, Alistair MacDonald, about to do battle with the local levy of 500 Stewarts and Robertsons, who resented this intrusion into their Clan territory. The appearance of Montrose, however, united the two sides, so he had thus found himself an army.

His aims were to raise Scotland for the king and to cause such an uproar in so doing, that the Government would be forced to draw off troops from Leslie's army to cope with him, thus relieving the pressure on Charles. A year and five battles later, he had succeeded in those objects and was now poised for the final blow, which would give him control of Scotland.
In August, 1645, Montrose had an army of 4,500 infantry and 500 cavalry assembled at Dunkeld, in Perthshire. His infantry were principally highlanders drawn from a number of Clans, whilst the cavalry were composed of Gordons and Ogilvies with the addition of gentlemen volunteers from many families, including the Livingstons and Flemings. Most were seasoned campaigners and were probably the best troops in Britain at the time - including Cromwell's Ironside.

The government's chosen general in Scotland was William Baillie of Letham, a sound professional soldier and one of Leslie's major - generals sent north to take charge. Montrose knew him already, having beaten him in battle at Alford in Aberdeenshire.

Baillie was at Perth attending the meeting of the Scottish Estates. He had been given an army of some 6,000 foot and 800 horse; his foot were a mixture of new levies from Fife of which he though very little, plus a number of regular regiments withdrawn from Leslie and remnants of other forces already defeated by Montrose. The cavalry was mainly regular dragoons. In addition to these troops, the Earl of Lanark had raised a levy of 1,000 infantry and 500 cavalry from his brother, Hamilton's estate in Clydesdale, and was en route north to join the main body.

When Montrose learned of this, he resolved to insert his own army between the other two. Marching from Dunkeld with the speed that characterised all his movements, he slipped past Baillie and travelling via Kinross, Glenfarg and Alloa, he crossed the Forth by the Fords of Frew above Stirling, circumnavigating the fortress town and crossed the Carron by ford on the site of the later Carron Bridge, marching south on the drove road on the route of the present Tak - Ma - Doon Road. By nightfall on the 14th August, the army was camped in a meadow near Colzium, now covered by Townhead Reservoir, and in an area around Colzium Castle.

It was not long before Baillie learned of Montrose's advance, but it took a little time for its purpose to become apparent. Realising that his opponent had gained an advantage and that Lanark was in some considerable danger, he moved in haste and, taking the chord of Montrose's arc, reached Stirling by the line of the modern A9 road. On the same night as Montrose reached Colzium, Baillie was only three miles off at Hollinbush (Hollinbush, Banknock). He arrived late and his men had little rest.

He was well served by his scouts and local people, thus he knew exactly where the Royalists lay. At dawn the next morning his troops were on the move and, marching directly across country, reached a point close to, and just south of, the modern village of Banton. Here the Covenanters were on the higher ground around the eastern rim of the hollow occupied by the Royalist infantry. It was a fine summer morning, already warm, with the promise of great heat to come.
The Highland troops were clearly visible, leisurely cooking their breakfast around hundreds of little bivouac fires, obviously not in the least disturbed by the arrival of the main army of their enemies. Having a healthy respect for them, and appreciating that his own forces were already hot, dusty and somewhat tired, Baillie decided to take post where he was and wait events. If and when Lanark appeared, he had Montrose between two fires, and if the general decided to attack Lanark, being the weaker force, then Baille could take him from the rear. Likewise, if Montrose attacked him, Lanark could provide support.

Although that was Baille's sound decision, he was not allowed to adhere to it. With him was a substantial body of the Committee of Estates, well seasoned with black-robed Calvinistic ministers of the Scottish Kirk. These gentlemen considered themselves to be the Elect of God and therefore better able to conduct a battle than their general. They were afraid that Montrose might escape to the Highlands, and they wanted to effect a junction with Lanark. The result was an order to Baille to march his army around the northern perimeter of the high ground flanking Montrose's position, to the area of Colzium Castle. Now, a flank march is a difficult and very dangerous manoeuvre at the best of times but, in this case, in full view of an alert and active foe such as Montrose's Highlanders, it was a suicidal one. Baille protested vigorously, but was over-ruled and was told to re-assemble his army in column and move accordingly. The force set off, the cavalry leading, and made a circuit of Banton Burn and then followed the line of the Drum Burn.
Montrose watched this with astonishment, then acted speedily. Bidding his men to cast off their plaids for ease of movement, he sent the Gordon cavalry against the nose of the column and the body of MacLean infantry to seize the farmsteadings of Auchinvalley, lying between his main body and the Covenanting centre. Reinforcing both units, the first with both cavalry and infantry, the latter with MacDonald foot, he stopped the column's advance with the first attack and broke it with the second.

The next order was for general attack; the Highlanders surged up the slopes about them in seconds and found the Covenanting army already broken and in retreat. The retreat became a rout, a terrible slaughter, some three-quarters of the troops perished dismally on the field under the Highland broadswords. Baille himself fled south with an escort of cavalry, but was caught in the notorious Dullatur Bog, a deep and treacherous marshy area lying between the head waters of the Kelvin and the Bonny. He managed to win clear eventually, though leaving most of his escort behind. He reached his cousin's house at Castle Cary, and then went on to greater safety at Stirling Castle. More than a hundred years later, during the cutting of the Forth and Clyde Canal, the bodies of several troopers, one still seated on a horse, were recovered from the Bog.
Lanark's forces were told of the disaster and scattered for home at once. Lanark himself and the other leaders raced across the Border and, at last, Montrose found himself undisputed master of Scotland.
It was too late for the King, however; Naseby had been fought and his cause was in ruins. A month after Kilsyth, the Scots army in England came marching home and took Montrose by surprise whilst he was with a small bodyguard at Philiphaugh in the Borders. Montrose just managed to escape, but is rule was over and the Covenanters were once more in control.
The site of Montrose's camp at Colzium is now covered by the waters of Townhead Reservoir, established in the late 18th century. Round its perimeter, a glance at the map reveals names such as Baggage Knowe, Slaughter Howe, Drum Burn, and Bullet Knowes, to remind us of the events that took place there. Several artefacts from this period have been found, including a broadsword and several cannonballs, apparently dropped by Montrose's army whilst camped at Colzium.
- Article by unknown author from Cumbernauld & Kilsyth District Council