Dunbar Castle stood on a sea-rock 29 miles up the coast from Berwick, controlling the road north toward Edinburgh. Its master, Patrick, Earl of March, had thrown in his lot with the English king. But his wife, Marjory Comyn, was the sister of the Earl of Buchan and a Scottish patriot to her bones. While the earl rode with Edward, Marjory opened the gates of Dunbar to her fellow Scots. To Edward, this was unacceptable. He sent his lieutenant John de Warenne, 6th Earl of Surrey, north with a strong force of knights to take the castle back. There was a complication: de Warenne was King John Balliol's father-in-law, marching north to break a fortress held in the name of his daughter's husband. The Comyns sent urgent word to Balliol, who was camped with the main Scottish army at nearby Haddington, asking for relief.

Balliol did not come himself. He had shown poor judgment as a commander, and he would show poorer still by sending out only a portion of the Scottish host instead of marching with the full strength of his army. The detachment advanced toward Dunbar. What happened on the field on 27 April 1296 was over quickly. The Scots, holding high ground, broke formation when they thought English knights below them were retreating; in fact the English were merely manoeuvring around broken ground. The Scots came down to pursue, found themselves charged in disorder by re-formed English heavy cavalry, and were routed. Most of the field casualties were among the foot soldiers, but the captured Scottish knights were taken south as prisoners. The campaign of 1296 was effectively over.

What followed was the systematic humiliation of a kingdom. James, the hereditary High Steward of Scotland, surrendered the great fortress of Roxburgh without a fight. Others followed. Only Edinburgh Castle held out a week against Edward's siege engines. Stirling Castle, guarding the crossing of the Forth, was abandoned to a single porter who handed the keys to Edward when he arrived. King John fled north, reached Perth on 21 June, and there received the English king's terms. At Kincardine Castle on 2 July John confessed to rebellion. Five days later at Stracathro he renounced his treaty with the French. The final humiliation came on 8 July at Montrose. Antony Bek, the formidable Bishop of Durham, ripped the red and gold arms of Scotland from John's surcoat, leaving him with the empty coat that gave him his nickname: Toom Tabard, the empty surcoat. The phrase still echoes in Scottish memory.

John and his son Edward Balliol went south into captivity. Soon after them went the King of England, riding in triumph through a Scotland he believed he had conquered, with the Stone of Scone in his baggage train along with the other relics of Scottish nationhood. He took the stone to Westminster Abbey, where it would sit beneath the English coronation chair for the next seven centuries. The Wars of Scottish Independence had begun. Within a year William Wallace would raise the standard of resistance at Lanark; within nine years Robert the Bruce would be crowned at Scone; within eighteen years Bannockburn would settle the question. But none of that was visible from the field outside Dunbar on 27 April 1296, where the Scottish foot lay dead in numbers the chroniclers did not bother to count precisely.

The Inventory of Historic Battlefields in Scotland added the Dunbar site in 2012. Historic Environment Scotland has noted that no archaeological discoveries have been reported from the battle site, and a 2007 dig failed to yield any battle-related finds. Weaponry and metalwork from 1296 may still lie undiscovered in the topsoil somewhere west of the modern town, in the gentle ground where the Scots first held high ground and then came down off it. The castle itself, much fought over again in the centuries that followed, was finally slighted by act of the Scottish Parliament in 1567. Its ruins stand above the modern harbour of Dunbar, weathered and incomplete, anchoring a story that started here in the spring of 1296 and that Scots have been arguing about ever since.