The Battle of Brandywine, also known as the Battle of Brandywine Creek, was fought between the American Continental Army of General George Washington and the British Army of General Sir William Howe on September 11, 1777. The forces met near Chadds Ford, Pennsylvania. More troops fought at Brandywine than at any other battle of the American Revolution. It was also the second longest single-day battle of the war, after the Battle of Monmouth, with continuous fighting for 11 hours. After Washington's victory at the Battle of Princeton, he had moved his army into quarters near Morristown, New Jersey. He had spent the summer encamped in Watchung Mountains. When he learned of Howe’s movement southward, he marched his army south to Wilmington, Delaware, arriving on August 25. That same day, Howe landed his army at Elk Head. On July 8, Howe began embarking his 16,500 men on board the British naval transports at Sandy Hook, New Jersey. His intention was to sail via the Delaware Bay to the Delaware River, threatening Philadelphia and preventing Washington from reinforcing Maj. Gen. Horatio Gates's northern army against Lieutenant General John Burgoyne. In the process, Howe might force a battle against Washington. At 5:30 a.m. the British and Hessian troops began marching east along the "Great Road" from Kennett Square, advancing on the American troops positioned where the road crossed Brandywine Creek. The first shots of the battle took place about 4 miles west of Chadds Ford, at Welch's Tavern. The British continued to advance and encountered a greater force of continentals behind the stone walls on the Old Kennett Meetinghouse grounds.

The battle was fought at mid-morning around the meeting house while the pacifist Quakers continued to hold their midweek service. The main British column under General Cornwallis set out from Kennett Square at 5:00 a.m. Around 6 p.m., Washington and Greene arrived with reinforcements to try to hold off the British, who now occupied Meeting House Hill. Upon hearing the attack of Cornwallis's column, Knyphausen launched an attack against the weakened American center across Chadds Ford, breaking through the divisions commanded by Wayne and William Maxwell and forcing them to retreat and leave behind most of their cannons. Although Howe had defeated the American army, his lack of cavalry prevented its total destruction. Washington had committed a serious error in leaving his right flank wide open and nearly brought about his army's annihilation had it not been for Sullivan, Stirling and Stephen's divisions, which fought for time. Evening was approaching and, in spite of the early start Cornwallis had made in the flanking maneuver, most of the American army was able to escape. British and American forces maneuvered around each other for the next several days with only a few encounters such as the Battle of the Clouds on September 16 and the Battle of Paoli on the night of September 20–21. In a matter of days, the Battles of Saratoga, hundreds of miles to the north, provided a victory over a British force which Howe was supposed to join.