Governor's Island was also occupied as an outpost.

Of more intrinsic strength, but not at first concerned, strong works had been thrown up on either side of the North River, upon commanding heights eight miles above New York, to dispute the passage of ships.
The crucial weakness in this scheme of defence was that the shore of Long Island opposite the city was much higher than that of Manhattan.
If this height were seized, the city, and all below it, became untenable.

Here, therefore, was the key of the position and the chief station for the American troops.

For its protection a line of works was thrown up, the flanks of which rested upon Wallabout Bay and Gowanus Cove, two indentations in the shores of Long Island.

These Washington manned with nine thousand of the eighteen thousand men under his command.