On October 4, 1777, Washington marched about 11,000 men down four roads at night to hit the British camp at Germantown, north of Philadelphia, and by mid-morning the attack had come apart in thick fog. American casualties were about 650, of whom about 150 were killed, against British losses of around 530. It was the last large battle of the northern campaign that year.
The plan was the ambitious kind Washington liked and that rarely worked: four columns converging on the British lines at dawn, Sullivan's on the right, Greene's on the left, militia on the flanks and Wayne's division opening the attack. Everything had to arrive at once. Fog delayed Sullivan's column by about two hours. Wayne's men ran into the British light infantry in the dark.
The fight turned at the Chew House, a stone mansion on the road where about 120 men of the 40th Foot had barricaded themselves in. Wayne and then part of Sullivan's wing stopped to reduce it, cannonaded it without effect, and lost time and momentum while the main attack stalled in front of it. The building was never taken. It is still standing.
What finished the attack was a breakdown in contact. In the fog, with gunfire echoing off the hills, part of Sullivan's wing and part of Wayne's began shooting at each other about a mile behind the lines, and word ran through the ranks that the British were on the flank. The American line broke and walked back four miles before it could be rallied.
Howe did not pursue. Philadelphia had fallen on September 26, the British stayed there until June 1778, and the Continental Army went to Valley Forge in December, where about 2,000 men out of roughly 12,000 died over the winter. The French, who had been watching for evidence that the Americans could win a battle, signed the treaty of alliance in February 1778, four months after this defeat and six weeks after Saratoga.