The two particular dangers now to which the army was exposed were the danger of having its communication with New York cut off by the ships, and the danger of being approached by the enemy in front by siege operations, which the army was not prepared to meet. The first danger had existed ever since the arrival of the enemy, and had been provided for. All the batteries on Governor's Island and on both sides of the East River had been built to guard against it. In addition, ships had been sunk in the channel. Washington accordingly must have thoroughly canvassed the risks he ran in regard to his communications. _These alone had not decided him to retreat._ On the morning of the 29th, however, he first became aware of the second danger. It was not until then that the enemy fully developed their intention of advancing by trenches. After working all night, as Howe reports, they had thrown up by morning, as Little reports, a parallel sixty rods long and one hundred and fifty rods distant from Fort Putnam. Reed wrote, "They are intrenching at a small distance." In twenty-four hours at the farthest they would have come within very close range, and the hazardous alternative would have been forced upon us to attempt to drive them out of their own works. Washington well knew that, in view of the condition of his men and the great disparity of numbers, this could not be done. When, therefore, he became assured of Howe's intentions he acted promptly--_he determined to retreat_; and this determination he reached early on the morning of the 29th.
This is substantially the theory which Gordon presents as a fact, and it is most consistent with fact. Gordon's account is this: "The victorious army encamped in the front of the American works in the evening; and on the 28th at night broke ground in form about 4 or 500 yards distant from a redoubt which covered the left of the Americans. The same day Gen. Mifflin crossed over from New York with 1000 men; at night he made an offer to Gen. Washington of going the rounds, which was accepted. He observed the approaches of the enemy, and the forwardness of their batteries; and was convinced that no time was to be lost. The next morning he conversed with the General upon the subject, and said, 'You must either fight or retreat immediately. What is your strength?' The General answered, 'Nine thousand.' The other replied, 'It is not sufficient, we must therefore retreat.' They were both agreed as to the calling of a Council of war; and Gen. Mifflin was to propose a retreat. But as he was to make that proposal, lest his own character should suffer, he stipulated, that if a retreat should be agreed upon, he would command the rear; and if an action the van."