King Edward III of England was happy to cause trouble for his northern neighbour and tacitly supported an attempt to place Balliol on the Scottish throne.

A Scottish army at least ten times stronger occupied a defensive position on the far side of the River Earn.

Unable to break the line of English men-at-arms, the Scots became trapped in a valley with fresh forces arriving from the rear pressing them forward and giving them no room to manoeuvre, or even to use their weapons.

[1] After the 30 years of warfare which followed, the newly crowned 14-year-old King Edward III was nearly captured in the English disaster at Stanhope Park.

In 1331, under the leadership of Edward Balliol and Henry Beaumont, Earl of Buchan, the disinherited Scottish nobles gathered in Yorkshire and plotted an invasion of Scotland.

David II's regent was an experienced old soldier, Thomas Randolph, Earl of Moray, who was appointed to the role of guardian of Scotland.

[7] While they were underway, the Scots selected Donald, Earl of Mar, as the new guardian of Scotland, and so also regent for the young David.

Knowing Mar to be commanding the troops on the northern shore of the firth, Balliol landed there, at Wester Kinghorn (present day Burntisland),[8] on 6 August 1332.

Mar withdrew his main force to the capital, Perth, amalgamated the survivors of Kinghorn and sent out a general call for reinforcements.

Buoyed by their victory, Balliol and Beaumont's force completed their disembarkation and marched to Dunfermline, where they foraged, looted a Scottish armoury and then headed for Perth.

[16] The Scottish army under Mar took up a position on the north bank of the River Earn,[17] 2 miles (3 km) south of Perth, and broke down the bridge.

[23] The Scots were content to rest in their defensive positions, while planning to send a portion of their army on a wide outflanking manoeuvre the next day.

[24] The Scots were so confident of victory that some started their celebrations that evening, according to a contemporary source "playing, drinking and making merry" late into the night.

The English believed they had overcome the main Scottish force, but were disabused at dawn when they saw the Scots advancing against them in two large bodies.

The Scots in their haste had allowed themselves to be channelled by the terrain and all of them attacked the English men-at-arms in the centre, ignoring the longbowmen on the valley sides.

Harassed by the longbowmen, the Scots on the flanks pressed closer to their main body, further compressing it and hampering the freedom of movement of its members.

[33] Mar's schiltron, which was also rushing towards the English, became disorganised due to its haste and was similarly channelled by the steep valley sides.

[25] In the centre of the Scottish mass the result was literally suffocating; men were pressed too tightly together to be able to breathe and any who lost their footing were trampled to death.

The survivors of Bruce's schiltron attempted to extricate themselves, adding to the confusion and making easy targets for the English men-at-arms.

In any event, before long the Scottish host had exhausted its own supplies, stripped the surrounding countryside of food and dispersed.

[43] Balliol was crowned King of Scots at Scone – the traditional place of coronation for Scottish monarchs[44] – on 24 September 1332.

[45] Within two months Balliol granted Edward III Scottish estates to a value of £2,000, which included "the town, castle and county of Berwick".

[46] Edward III dropped all pretence of neutrality, recognised Balliol as King of Scots and made ready for war.

[47] After the defeat of the Scots at the Battle of Halidon Hill in July 1333 by the English Balliol was reinstated on the Scottish throne.

[50][51] The modern historian Ranald Nicholson states that Edward III copied the tactics used at Dupplin Moor – "all the men-at-arms dismounted, while archers were posted on either flank" – in the English victories at Halidon Hill and Crécy.