Above the fort were two batteries opposing those constructed by the British on Province and Carpenter's Islands, which were separated from Mud Island only by a narrow passage between four and five hundred yards wide.
The vessels of war, engaged in the defence of the Delaware, were partly in the service of the continent, and partly in that of the state of Pennsylvania, under a Commodore who received his commission from the state.

A misunderstanding took place between him and Lieutenant Colonel Smith, and also between him and the officers of the continental navy; and it required all the authority of the Commander-in-chief to prevent these differences from essentially injuring the service.
The garrison of fort Mifflin consisted of only three hundred continental troops, who were worn down with fatigue, and constant watching, under the constant apprehension of being attacked from Province Island, from Philadelphia, and from the ships below.
{October 29.} Having failed in every attempt to draw the militia of Jersey to the Delaware, General Washington determined to strengthen the garrison by farther drafts from his army.

Three hundred Pennsylvania militia were detached, to be divided between the two forts; and, a few days afterwards, General Varnum was ordered, with his brigade, to take a position about Woodbury, near Red Bank, and to relieve and reinforce the garrisons of both forts as far as his strength would permit.

The hope was entertained that the appearance of so respectable a continental force might encourage the militia to assemble in greater numbers.
Aware of the advantage to result from a victory over the British army while separated from the fleet, General Washington had been uniformly determined to risk much to gain one.

He had, therefore, after the battle of Germantown, continued to watch assiduously for an opportunity to attack his enemy once more to advantage.