It inspired them with confidence, and showed the world that though driven from the field of Brandywine they were still aggressive. It was now evident to Howe that he must open communication with New York by water, or his army would be in a state of siege. His attention was therefore turned to the defences of the Delaware which were held by the Americans. The most formidable of these was Fort Mifflin, situated on an island in the river a short distance below the mouth of the Schuylkill. Opposite this, at Red Bank, on the Jersey shore, was Fort Mercer, while four or five miles below, at Billingsport, was another fortification. Opposite these points _chevaux-de-frise_ were sunk in the channel, which were protected by the batteries and by a fleet of small vessels, known as the Pennsylvania navy, commanded by Commodore John Hazelwood. Besides these, there were several larger vessels which had been built by order of Congress. On the 19th of October Howe withdrew his troops from Germantown and encamped them behind his lines of intrenchments on the north side of the city. Before this he had erected batteries to attack Fort Mifflin. He now sent a body of men, under Colonel Stirling, over the river from Chester to capture the fort at Billingsport. The garrison there was not sufficient for the defence of the fort, and as the British approached they evacuated the post. By the 21st Admiral Howe succeeded in passing the lower _chevaux-de-frise_, and his vessels sailed up the river to a point nearly opposite Fort Mifflin. On the same day three battalions of Hessians, with artillery, crossed into Jersey from Philadelphia to attack Fort Mercer. They arrived before the fort on the afternoon of the 22d. It was commanded by Colonel Christopher Greene, of Rhode Island, who had with him but six hundred men. The fortifications were unfinished, but a strong redoubt, with an abatis, had been constructed. Donop summoned the garrison to surrender, and upon receiving a refusal formed his regiments for the attack. They rushed upon the embankments and passed the abandoned lines with little opposition. But when they charged the redoubt, they were met with a fire that nearly filled the ditches with killed and wounded. Most of the men retired in confusion, and those who attempted to scale the works were beaten back in a hand-to-hand conflict. It was intended that the fleet should coöperate with Donop; that the "Vigilant", with sixteen 24-pounders, should pass to the west of Fort Mifflin, while other vessels should engage Hazelwood and prevent his offering assistance to Greene. The plan failed, however, at all points. The "Vigilant" could not sail up the west channel, and Hazelwood was more than a match for the vessels sent against him. He drove them back, while some of his boats sailed close to the shore and poured an effective fire into the flank of Donop's column. It was in vain that Donop and his officers re-formed the men and led them back to the attack.