The same news brought gloom to the British in Philadelphia, for it had the stern meaning that the effort and loss involved in the capture of that city were in vain.

Washington held most of the surrounding country so that supplies must come chiefly by sea.
With a French fleet and a French army on the way to America, the British realized that they must concentrate their defenses.

Thus the cheers at Valley Forge were really the sign that the British must go.
Sir William Howe, having taken Philadelphia, was determined not to be the one who should give it up.

Feeling was bitter in England over the ghastly failure of Burgoyne, and he had gone home on parole to defend himself from his seat in the House of Commons.

There Howe had a seat and he, too, had need to be on hand.