It was mid afternoon before the heavily outnumbered English forces were deployed, their divisions having become strung out from the crossing of the burn and bog in foul weather. During this time when the English were particularly vulnerable James held his position.

Hostilities opened with an exchange of cannon fire. Whereas the Scottish bombardment was fairly ineffective, the English gunners got the range quickly and inflicted heavy casualties on the Scottish infantry. Those on the Scottish left, the Borderers, were unable to stand the barrage and, contrary to orders to stand firm, charged down the hill under their commander Lord Home. The charge was effective and the troops on the English right broke and fled the field. However, Home was unable to take advantage of the initial attack as his undisciplined Borderers showed more interest in looting rather than reforming and attacking the exposed English flank. By the time Home had restored some order the English cavalry, under Dacre, counter-attacked and halted the Borderers' advance. Both forces then withdrew slightly, weighing each other up silently but neither willing to engage once more.

Meanwhile in the centre of the field James, having witnessed the success of Home’s initial charge, and no doubt expecting him to follow it up with an assault on the English right flank, led the heavy infantry to the attack. This was the first massed attack in Britain by infantry carrying the modern European pike, which was to dominate infantry warfare for much of the 16th and 17th century across Europe. The Scots had been supplied with and trained in the use of the pike, a 16 or 18 foot long steel tipped pole, by their French allies. The English army of the north was still using the far shorter 'bill' that had been the standard weapon of the late medieval infantry. 

The momentum of the Scottish charge carried them crashing into the English line pushing it back, perhaps as far as the village church, but there the line held. On the Scottish right the Highlanders had so far taken no part in the battle. They had however been paying close attention to a body of English troops approaching the foot of Branxton Hill. Deciding to hold their position the Highlanders awaited the English advance, but this proved to be a mistake as the advance to the bottom of the hill was a feint. The main body, under Stanley, was advanced around the right of the Highlanders using the cover of a ravine. Emerging from the dead ground the English troops unleashed a devastating flight of arrows into the unarmoured Highlanders, following it up with a charge. Like their countrymen in battles such as Northallerton in the 12th century, Dupplin Moor and Hallidon Hill in the 14th, right through to Pinkie in the mid 16th century, the Highlanders broke and fled in the face of the English arrowstorm.

Back in the centre of the field James had called for his reserves who, under Bothwell, had marched down the hill and headed for the left of the centre, where they considered the Scottish attack to be weakest. However, following his success on the hill, Stanley now led his men back into the fray and attacked Bothwell’s reserves in the rear. At the same time Dacre, no longer fearing further assault from the Borderers, led the bulk of his cavalry in an assault on Bothwell’s flank. The combined attack made short work of the Scots who were rapidly dispatched.

Dacre and Stanley now joined forces and launched an attack on the rear of the main Scottish army, in which James fought. Heavily outnumbered and with the enemy on all sides the Scots fought on. It has been argued that a major factor in teh Scottish defeat was their lack of expertise in pike tactics, and in this context it is interesting to note that in this last stand the Scots reverted to their traditional weapons of sword and axe. But the outcome was in little doubt and King James died on the field along with much of the Scottish nobility, in what is arguably the greatest defeat a Scottish army ever suffered on the battlefield.