After a stiff fight, Howe's wing broke through the newly formed American right wing which was deployed on several hills. At this point Lieutenant General Wilhelm von Knyphausen attacked Chadds Ford and crumpled the American left wing. As Washington's army streamed away in retreat, he brought up elements of General Nathanael Greene's division which held off Howe's column long enough for his army to escape to the northeast. Polish General Casimir Pulaski defended Washington's rear assisting in his escape. The defeat and subsequent maneuvers left Philadelphia vulnerable. The British captured it two weeks later on September 26, resulting the city falling under British control for nine months, until June of 1778.