Philadelphia served no purpose but to divide and distract British enterprise.  Absolutely dependent for maintenance upon the sea, the forces in it and in New York could not cooeperate; they could not even unite except by sea.  When Clinton relieved Howe as commander-in-chief, though less than a hundred miles away by land, he had to take a voyage of over two hundred miles, from New York to Philadelphia, half of it up a difficult river, to reach his station; and troops were transferred by the same tedious process.  In consequence of these conditions, the place had to be abandoned the instant that war with France made control of the sea even doubtful.  The British held it for less than nine months in all.

During 1777 a number of raids were made by British combined land and sea forces, for the purpose of destroying American depots and other resources.  Taken together, such operations are subsidiary to, and aid, the great object of interrupting or harassing the communications of an enemy.  In so far, they have a standing place among the major operations of war; but taken singly they cannot be so reckoned, and the fact, therefore, is simply noted, without going into details.  It may be remarked, however, that in them, although the scale was smaller, the Navy played the same part that it now does in the many expeditions and small wars undertaken by Great Britain in various parts of the world; the same that it did in Wellington’s campaigns in the Spanish peninsula, 1808-1812.  The land force depended upon the water, and the water was controlled by the Navy.

[Footnote 18:  This was just below the mouth of the Schuylkill, a short distance below the present League Island navy yard.]

CHAPTER IV

WAR BEGINS BETWEEN FRANCE AND GREAT BRITAIN.  BRITISH EVACUATE
PHILADELPHIA.  NAVAL OPERATIONS OF D’ESTAING AND HOWE ABOUT NEW YORK,
NARRAGANSETT BAY, AND BOSTON.  COMPLETE SUCCESS OF LORD HOWE.  AMERICAN
DISAPPOINTMENT IN D’ESTAING.  LORD HOWE RETURNS TO ENGLAND.

1778

The events of 1777 satisfied the French government that the Americans had strength and skill sufficient to embarrass Great Britain seriously, and that the moment, therefore, was opportune for taking steps which scarcely could fail to cause war.  On the 6th of February, 1778, France concluded with the United States an open treaty of amity and commerce; and at the same time a second secret treaty, acknowledging the independence of the late Colonies, and contracting with them a defensive alliance.  On the 13th of March, the French Ambassador in London communicated the open treaty to the British government, with the remark that “the United States were in full possession of the independence proclaimed by their declaration of July 4th, 1776.”  Great Britain at once recalled her Ambassador, and both countries prepared for war, although no declaration was issued.  On the 13th of April, a French fleet of twelve ships of the line and five frigates, under the command of the Count d’Estaing,[19] sailed from Toulon for the American coast.  It was destined to Delaware Bay, hoping to intercept Howe’s squadron.  D’Estaing was directed to begin hostilities when forty leagues west of Gibraltar.