These two circumstances enabled him to form an army in the Jerseys sufficient for the reduction of fort Mercer, without weakening himself so much in Philadelphia as to put his lines in hazard.

Still deeming it of the utmost importance to open the navigation of the Delaware completely, he detached Lord Cornwallis about one in the morning of the 17th, with a strong body of troops to Chester.

From that place, his lordship crossed over to Billingsport, where he was joined by the reinforcement from New York.
{November 17.} General Washington received immediate intelligence of the march of this detachment, which he communicated to General Varnum with orders that fort Mercer should be defended to the last extremity.

With a view to military operations in that quarter, he ordered one division of the army to cross the river at Burlington, and despatched expresses to the northern troops who were marching on by brigades, directing them to move down the Delaware on its northern side until they should receive farther orders.
[Sidenote: Fort Mercer evacuated.] Major General Greene, an officer who had been distinguished early in the war by the Commander-in-chief for the solidity of his judgment and his military talents, was selected for this expedition.

A hope was entertained that he would be able, not only to protect fort Mercer, but to obtain some decisive advantage over Lord Cornwallis; as the situation of the fort, which his lordship could not invest without placing himself between Timber and Manto Creeks, would expose the assailants to great peril from a respectable force in their rear.