The army left Blair Atholl on December 11th in unusually mild weather. Marching to Loch Tummel and on to Loch Tay and down Glen Finnan to Tyndrum. Here the army split into three war bands for the decent into Inveraray itself. The Royal army marched into Inveraray but were unable to take the castle. Argyll also escaped them by sailing down Loch Fyne.
The army stayed at Inveraray until the beginning of January when it re-grouped. It was now a well fed and well equipped army, laden down with the spoils of war and a vast heard of cattle. On the 14th of January the army left Inveraray and headed north up Glen Shira to Kilchurn Castle. From there they continued up the pass of Brander to Glen Etive where tradition has it that part of the army turned northwards up by Loch Etive and Glen Etive to Glencoe, whilst the Bulk of the army entered Glencoe via the river Conna and Meall Mor.

At Glencoe they climbed over the devil’s staircase and across the high passes that took them to the north side of Ben Nevis and down into the Great Glen above Inverlochy Castle. A day later they continued up the Glen finally halting at Kilcummin (Fort Augustus) to take stock. By now much of the army had returned home with their booty as was the custom of the highlanders, leaving barely 1500 men. Montrose was aware that the Covenant army was ahead of them at Inverness, it was however due to the arrival of Ian Lom MacDonald the Bard of Keppoch that alerted him to the fact that Argyll was pursuing him with an army that was now barely thirty miles behind him at Inverlochy.
Montrose concluded that his small army wouldn’t stand a chance against the combined strengths of the two armies, he therefore elected upon a daring strategy to defeat Argyll before they could join together. Instead of marching back down the Great Glen Montrose took a circuitous route over the hills above the glen and across the foothills of Ben Nevis.

Tradition has it that it was Ian Lom MacDonald who guided them through the mountain passes, an army battling through heavy snow and swollen rivers with only the supplies that they could carry to sustain them. The army left Kilcummin and climbed Glen Tarff towards the pass of Corrieyarack. From here the exact route to Glen Roy is unclear, it was however a cold and tired army that camped down at Keppoch 18 miles from Inverlochy. On the second day they continued down Glen Roy and forded the Spean. From here they followed the Cour river into the Leanachan Forest and across the foothills of Ben Nevis. They arrived on the evening of Saturday 1st February, having completed what was later described as the most incredible flanking march in British history.
The army spent an uncomfortable night on the hillside, unable to light fires for fear of betraying their strength. For though Argyll was aware that a war band was in the area he had no reason to believe that the whole of Montrose’s army had completed what was to all intents and purposes an unthinkable if not impossible march. It was therefore a shattering blow to the morale of the Covenanting army to behold the full might of the Royal army before them on the morning of February 2nd. How could they be there? They were meant to be thirty miles away!

What followed was a bloody battle, the Covenant forces fought bravely but the Royalists despite being out numbered two to one carried the day. For the Covenanters and Clan Campbell it was a disaster with an estimated 1500 of their men slain. Once again however Argyll escaped the clutches of Montrose, this time sailing away before battle was joined.