After the capture of Philadelphia on September 26, 1777, and of the failure of the American surprise attack against the British camp at the Battle of Germantown on October 4, the Americans tried to deny the British use of the city by blockading the Delaware River. To that end, two forts were constructed commanding the river. One was Fort Mercer on the New Jersey side at Red Bank (now National Park, New Jersey). The other was Fort Mifflin on Mud Island, in the Delaware River just south of the confluence of the Schuylkill River, on the Pennsylvania side opposite Fort Mercer. So long as the Americans held both forts, the British army in Philadelphia could not communicate with the outside world or be resupplied. In addition to the forts, the Americans possessed a small flotilla of Continental Navy ships on the Delaware supplemented by the Pennsylvania State Navy, all under the command of Commodore John Hazelwood.
On October 19, General Sir William Howe, the commander of the British army, evacuated his camp at Germantown and pulled his forces inside the city of Philadelphia. He sent a part of his force to capture the two American forts denying him use of the Delaware River. Earlier, Howe had sent a group of men via Webb's Ferry, at the mouth of the Schuylkill River, to marshy Providence Island (actually on the Pennsylvania mainland by Mud Island) to construct artillery batteries to bombard Fort Mifflin. The first bombardment of Fort Mifflin came on October 11. This was merely a desultory attack which convinced the British to expand and improve their batteries.
Meanwhile, 2,000 Hessian troops under the command of Colonel Karl von Donop landed at Cooper's Ferry in Gloucester City, New Jersey, about four miles (6 km) upriver from Fort Mercer, and made preparations to attack the fort, located on the high ground at Red Bank.
Von Donop, who had had three regiments defeated and captured nearly a year earlier at the Battle of Trenton, was eager to avenge what he co...