At Guilford Courthouse, fighting along the third line swayed back and forth across the contested stream valley. On the high ground overlooking the valley stood the American third line, a mix of seasoned Continentals and new recruits, waiting tensely for the enemy after the British had overrun the first and second lines. When the British Guards emerged from the woods below, the fiercest fighting of the day ensued. As the British overwhelmed the left flank, Lt. Col. William Washington’s cavalry slashed in from the right and inflicted heavy casualties. Cornwallis then ordered British Royal Artillery to fire canister and grapeshot into the melee, driving back the American cavalry and Maryland Continentals. When the British regrouped and began to outflank this line, Greene directed an orderly retreat. The British gained the field and won a tactical victory, but at crippling cost: a quarter of Cornwallis’s army, 500 of the finest British troops in America, were killed or wounded in these fields and thickets, and seven months later came the surrender at Yorktown.