The attention of both armies was most principally directed to the forts below Philadelphia.
The loss of the Delaware frigate, and of Billingsport, greatly discouraged the seamen by whom the galleys and floating batteries were manned. Believing the fate of America to be decided, an opinion strengthened by the intelligence received from their connexions in Philadelphia, they manifested the most alarming defection, and several officers as well as sailors deserted to the enemy. This desponding temper was checked by the battle of Germantown, and by throwing a garrison of continental troops into the fort at Red Bank, called fort Mercer, the defence of which had been entrusted to militia. This fort commanded the channel between the Jersey shore and Mud Island; and the American vessels were secure under its guns. The militia of Jersey were relied on to reinforce its garrison, and also to form a corps of observation which might harass the rear of any detachment investing the place.
Measures taken by General Washington for cutting off supplies from Philadelphia.
To increase the inconvenience of General Howe's situation by intercepting his supplies, six hundred militia, commanded by General Potter, crossed the Schuylkill, with orders to scour the country between that river and Chester; and the militia on the Delaware, above Philadelphia, were directed to watch the roads in that vicinity.
The more effectually to stop those who were seduced by the hope of gold and silver to supply the enemy at this critical time, congress passed a resolution subjecting to martial law and to death, all who should furnish them with provisions, or certain other enumerated articles, who should be taken within thirty miles of any city, town or place, in Jersey, Pennsylvania, or Delaware, occupied by British troops.
These arrangements being made to cut off supplies from the country, General Washington reoccupied the ground from which he had marched to fight the battle of Germantown.
Attack upon Fort Mifflin.
Meanwhile, General Howe was actively preparing to attack fort Mifflin from the Pennsylvania shore. He erected some batteries at the mouth of the Schuylkill, in order to command Webb's ferry, which were attacked by Commodore Hazlewood, and silenced; but, the following night, a detachment crossed over Webb's ferry into Province Island, and constructed a slight work opposite fort Mifflin, within two musket shots of the block-house, from which they were enabled to throw shot and shells into the barracks. When day-light discovered this work, three galleys and a floating battery were ordered to attack it, and the garrison surrendered. While the boats were bringing off the prisoners, a large column of British troops were seen marching into the fortress, upon which the attack on it was renewed, but without success; and two attempts made by Lieutenant Colonel Smith to storm it, failed. In a few nights, works were completed on the high ground of Province Island which enfiladed the principal battery of fort Mifflin, and rendered it necessary to throw up some cover on the platform to protect the men who worked the guns.
The aids expected from the Jersey militia were not received. "Assure yourself," said Lieutenant Colonel Smith, in a letter pressing earnestly for a reinforcement of continental troops, "that no dependence is to be put on the militia; whatever men your excellency determines on sending, no time is to be lost." The garrison of fort Mifflin was now reduced to one hundred and fifty-six effectives, and that of Red Bank did not much exceed two hundred.
In consequence of these representations, Colonel Angel, of Rhode Island, with his regiment, was ordered to Red Bank, and Lieutenant Colonel John Greene, of Virginia, with about two hundred men, to fort Mifflin.