Then for nearly three years they gave their chief attention to New York City and its environs, and to Jersey down to, and including, Philadelphia.

On the whole, except for keeping their supremacy in New York, they had lost ground steadily, although they had always been able to put more men than the Americans could match in the field, so that the Americans always had an uphill fight.

Part of this disadvantage was owing to the fact that the British had a fleet, often a very large fleet, which could be sent suddenly to distant points along the seacoast, much to the upsetting of the American plans.
The French Alliance, ratified during the spring, not only gave the Americans the moral advantage of the support of a great nation, but actually the support of a powerful fleet.

It opened French harbors to American vessels, especially privateers, which could there take refuge or fit out.

It enabled the Continentals to carry on commerce, which before the war had been the monopoly of England.