At Guilford Courthouse on 15 March 17812, the British under Cornwallis drove Nathanael Greene's larger American army from the field but lost about a quarter of their men doing it. Greene had planned exactly this, trading ground for British blood. The ruinous cost forced Cornwallis to abandon the Carolinas and march into Virginia, a road that ended in his surrender at Yorktown later that year.
Nathanael Greene never beat Cornwallis in a battle, and never needed to. At Guilford Courthouse he let the British win the field, and made the winning so expensive that it broke their army in the South.
Part of The greatest battles of the American Revolution · Before: Battle of Cowpens · Next: Siege of Yorktown
Greene's war of exhaustion
After taking command of the shattered southern army, Nathanael Greene refused to risk everything in one battle. He led Cornwallis on an exhausting chase across the Carolinas3, then turned at Guilford Courthouse to fight on ground of his own choosing, ready to trade the field for enemy casualties.
The three lines
Greene drew up his army in three successive lines1, with militia in front and his Continental regulars behind1. The militia were to fire a volley or two and fall back, forcing the British to fight their way through line after line and pay for every yard.
The British attack
Cornwallis's veterans broke through the forward lines but met hard fighting at the last. At the crisis, with his own infantry locked in a melee, Cornwallis's guns fired grapeshot into the melee4; tradition says he deliberately fired through his own men, though recent research argues their target was the charging American cavalry and only a few British soldiers were hit. Greene, unwilling to lose his army, withdrew in good order.5
A victory too dear
Cornwallis held the field and claimed the victory, but he had lost roughly a quarter of his men, including many irreplaceable officers. The British politician Charles James Fox reportedly remarked that another such victory would ruin the British army2.
Why Guilford Courthouse mattered
Too weak to hold the Carolinas, Cornwallis fell back to Wilmington to refit and then marched into Virginia, where he was trapped and forced to surrender at Yorktown. Greene's strategy of bleeding the enemy while losing battles had won the South. See also Cowpens.