Howe decided to attempt to outflank Washington. He sent 5,000 troops under Lieutenant-General Wilhelm von Knyphausen to feint against Washington's centre while another force under Cornwallis was sent on a flanking move around the American right, commanded by General John Sullivan. Sullivan failed to extend his patrols far enough to detect the British move, although Cornwallis had marched his men 18 miles to achieve his flanking manoeuvre.
This lengthy march meant that Cornwallis was unable to attack immediately, and Sullivan was able to turn his troops to face the new attack. Despite this, when Cornwallis attacked his men were able to break Sullivan's line. Only support from Nathanael Greene's division prevented an immediate collapse, but they too were forced to fall back under British fire. At the same the American centre, weakened by Greene's move, was pushed back by von Kynphausen, whose feint now became a serious attack.
The stage was almost set for the decisive victory in battle that the British desired, but it was not to be. A combination of the late hour, with darkness descending, the tiredness of Cornwallis' troops and the British lack of cavalry prevented any truly devastating pursuit, while the American forces managed to withdraw in unexpectedly good order, a sign of the increasing quality of the Continental Army. Despite this, Brandywine was a major British victory. Howe suffered 576 casualties, compared to 900 American. The British also captured most of the American artillery and 100 prisoners. Two weeks later Howe's army entered Philadelphia.