George de Dunbar, 10th Earl of March, was the man waiting on Nesbit Moor that summer day. He had been one of the most powerful magnates in southern Scotland, but a quarrel over a broken marriage betrothal with the rival Douglas family had driven him to renounce his Scottish allegiance and offer his sword to Henry IV of England. The Scottish crown forfeited his earldom in his absence. By 1402 he was leading English soldiers against his own countrymen, drawing his force mainly from the strong English garrison at Berwick-upon-Tweed, the great fortified town at the mouth of the Tweed where the border met the sea. Local knowledge mattered in border warfare, and Dunbar had it. He knew the country his enemy would be crossing, knew the tracks they would take home with their stolen cattle, and chose his ground.

The Scottish raid that summer was substantial. Around 12,000 troops had crossed earlier into Cumberland and pillaged the country around Carlisle. The smaller force returning across Berwickshire was a fraction of that, but at 400 men still outnumbered Dunbar's English two to one. It did not matter. Surprise, discipline, and the advantage of waiting on chosen ground favoured the smaller force. Sir Patrick Hepburn, younger of Hailes, was killed in the fighting. Sir John Haliburton of Dirleton, Sir Robert de Lawedre of Edrington, Sir John Cockburn, and Sir Thomas Haliburton were all captured and led south as ransom prizes. Sir Robert Lawder remained a prisoner long enough that no record survives of when he was finally freed; a safe-conduct from Henry IV in June 1411 shows him already at liberty, suggesting nearly a decade of captivity.

News of the fight reached Henry IV at Harborough on 30 June, just eight days after the battle. The king was preparing to march into Wales to suppress the rebellion of Owain Glyndwr, but the scale of the Scottish incursion changed his calculations. He delayed his Welsh campaign to deal with what he now expected would be a much larger Scottish invasion. He was right to worry. That autumn a Scottish army under Archibald Douglas, 4th Earl of Douglas, marched as far south as the River Wear, harrying English country until an English force met and crushed them at the Battle of Humbleton Hill. Nesbit Moor, the small skirmish on the Berwickshire field, had been the spark that lit the larger fire.

What remains of Nesbit Moor today is the name. The field where the Scots fell is still called Slaughter Field, a piece of local memory that has outlasted the chroniclers' brief notices and survived in the working landscape of the Kimmerghame Estate. The Swinton family, whose name appears in Scottish history as far back as the eleventh century, still holds the land. A few miles south runs the River Tweed; beyond it lies Northumberland, where the cattle had come from, and Berwick, where Dunbar's soldiers had been quartered. The names on the borderland map have changed remarkably little since 1402. Hailes Castle, Dirleton, Edrington: the surnames of the men captured here still attach to ruins, villages, and farms that anyone in East Lothian and the Merse will recognise.

Nesbit Moor was not exceptional. It was characteristic. For three centuries the Anglo-Scottish border existed in a state of permanent low-grade war punctuated by larger invasions, where the difference between an army and a raiding party blurred and where loyalty often followed family quarrels more than nationality. Scottish nobles fighting for English kings, English garrisons mounting ambushes against returning Scots raids, cattle as much the prize as territory, ransom as much a financial transaction as a military one. The small fight on Slaughter Field in 1402 mattered enough to delay a king's campaign and trigger a larger Scottish invasion, then faded into the working memory of a single Berwickshire farm.