Henry’s army advanced along the Roman road and when within 1200-600 yards the royal artillery appear to have opened fire. This revealed the royal deployment and the threat posed by their artillery. Instead of a frontal attack the Earl of Oxford decided to exploit the terrain and mount a flanking manoeuvre to attack the right wing of Richard’s army, where Norfolk commanded the vanguard. This involved the army turning north-westward, putting the sun at their back and using the marsh to protect their right flank. The success of these manoeuvres suggest that Richard may have made a major tactical blunder in his deployment by not protecting against such an outflanking move.

This was a classic move from the military manual of Vegetius. It forced Richard’s army to manoeuvre, probably constrained by the ground on which he had chosen to fight and especially by having such a wide battle array. The vanguard was normally the strongest 'battle' in an army, with the best trained and most experienced soldiers. An attack on the vanguard would thus be a reasonable tactic for a smaller force, concentrating almost all its troops into its own vanguard and hoping that if it could destroy the strongest 'battle' of the enemy army that rest would flee. This was an all or nothing bid to even the odds. But it depended upon the Stanleys' support from the sidelines detering Northumberland from supporting Richard's vanguard when it came under pressure and in supporting Henry should his tiny main battle come under attack, as indeed it did.

When the rebel vanguard had passed the marsh they wheeled to the right and this is when they were engaged by the royal vanguard. The infantry in the centre of the battle array comprised both archers and billmen, with the archers deployed to the fore to deliver the initial arrowstorm. But as the enemy advanced the archers would have needed to withdraw, to the protection of the main body of infantry, as the fighting transformed into a close quarter, hand to hand fight.