The British must unite their forces to meet the peril from France, and New York, as an island, was the best point for a defense, chiefly naval.

A move to New York was therefore urgent.

It was by sea that the British had come to Philadelphia, but it was not easy to go away by sea.

There was not room in the transports for the army and its encumbrances.

Moreover, to embark the whole force, a march of forty miles to New Castle, on the lower Delaware, would be necessary and the retreating army was sure to be harassed on its way by Washington.