Alarmed beyond measure at the suggested departure of the Boston squadron, Washington wrote a letter, which De Rochambeau signed with him, urging De Barras to turn his fleet toward the Chesapeake.

It was a skillfully drawn missive, an adroit mingling of appeals to honor and sympathy and of vigorous demands to perform an obvious duty.

The letter did its work, the diplomacy of Washington was successful, and De Barras suppressed his feelings of disappointment, and agreed to go to the Chesapeake and serve under De Grasse.
This point made, Washington pushed on his preparations, or rather pushed on despite his lack of preparations, and on August 17, as has been said, wrote to De Grasse to meet him in the Chesapeake.

He left the larger part of his own troops with Heath, to whom in carefully drawn instructions he intrusted the grave duty of guarding the Hudson and watching the British in New York.

This done, he gathered his forces together, and on August 21 the army started on its march to the south.