Unbeknownst to the Americans, General Charles Cornwallis led a sizable British force out of the city on a foraging expedition early that morning. Cornwallis was also apparently unaware of the Continental Army movement, and had planned to forage in the area just south of Matson's Ford. Employing a local resident named John Roberts (who despite protestations that he acted under duress, was convicted and hanged in 1778 for assisting Cornwallis) as a guide, Cornwallis crossed the Schuylkill at Middle Ferry, drawing a round of musket fire from the American picket there before it withdrew. Cornwallis then proceeded up the road toward Matson's Ford. His force consisted of brigades of British light infantry and grenadiers, one brigade of regular infantry, two troops of dragoons, and a detachment of German jägers. The force took with them six 6-pound cannons. Soon after, the militia stationed at the Black Horse Inn exchanged fire with the British troops. Outnumbered and flanked, the militia began to fall back in some confusion, taking casualties along the way. Reports were delivered to Potter, who was with the contingent located at Harriton House, indicating that the British were "advancing in force" up Gulph Road and towards his location. Potter stationed five regiments of militia between the British forces and Harriton House. However, the militia were quickly overrun and they hastily retreated back through Gulph Mills to Swede's Ford (present-day Norristown). The retreat was so chaotic that militiamen literally threw away their muskets and ammunition as they ran (an offense for which they would later be fined or publicly whipped). With the militia in retreat, Cornwallis discontinued pursuit and took up a strong position on the heights overlooking Matson's Ford. General Potter estimated his casualties at 5 or killed, 20 wounded, and 20 taken prisoner, although he also claimed he was "not able to assurtain" the full extent of his losses. He believed the British casualties to be higher than his. Jäger Captain Johann Ewald recorded that the British captured about 160 men in the battle "after a stubborn resistance". The day after the battle, two Continental Army divisions under the command of General John Sullivan constructed a temporary bridge made from wagons that had been lashed together, and began crossing at Matson's Ford. Those divisions had almost completed crossing the river when the British position on the heights was spotted. Sullivan quickly ordered a retreat back across the river, and destroyed the makeshift bridge behind him.