Fort Mercer and Fort Mifflin: The Battle for the Delaware River and the Importance of the American Riverine Defenses during Washington's Siege of Philadelphia

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Browne, Gregory Michael
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Western Illinois University
"This thesis presents an in-depth study of General William Howe's Philadelphia campaign and the ensuing battles with the American river defenses and Pennsylvania navy over control of the Delaware River. Through the available literature, and supported by abundant primary sources, a story unfolds of the siege of Philadelphia. A chronology of events moves the reader from Howe's decision to move on the American capital Philadelphia, through the capture of the city, Washington's subsequent encirclement of Howe, and the two generals' struggle to control the Delaware. In 1777, the British believed they could win the war in America by effectively cutting off the northern colonies form the rest of the rebellious colonies. Their strategy called for General John Burgoyne's army, consisting of British regulars, Hessian auxiliaries, Canadian volunteers, and Indians, to move south from Canada to Lake Champlain. He was to take Fort Ticonderoga, and proceed to Albany. General William Howe's army, supported by British warships under his brother Admiral Richard Howe, was to proceed up the Hudson, seize the American fortifications along the way, and link up with Burgoyne in Albany. The British also hoped that the threat they posed to the Hudson River valley, and its vital waterway, would force Washington to fight a general engagement, which they believed he would lose. During the summer of 1777, General Howe assembled an expeditionary force at New York City. However, he was not planning to move north, but rather to sail south, attack Pennsylvania, and capture the American capital. Howe was sure Washington would not allow the capital to fall and would be forced to fight a general engagement he could not win. Howe also was led to believe that upon his arrival in Pennsylvania he could count on strong local Loyalist support. The British government assumed that once Washington was defeated and Philadelphia was under British control, Howe could garrison the city with Loyalist troops and sail back north to the Hudson to complete his rendezvous with Burgoyne. Inexplicably, Howe squandered months of good campaigning weather, until finally in late July he sailed out of New York to Chesapeake Bay. Landing at Head of Elk, Maryland, he proceeded slowly towards Philadelphia. Washington moved his army from New Jersey to Philadelphia to stop the British advance, but was defeated at the battle of Brandywine, and forced to retreat. Howe captured Philadelphia on September 26, 1777. Howe had accomplished his mission but found he had placed himself in a precarious position. There was no great outpouring of Loyalist support. Washington's army, though beaten at Brandywine, was still intact and formidable. The Americans had encircled the British army and disrupted their long supply lines. American river forts and obstructions, in concert with Commodore John Hazelwood's Pennsylvania navy, had closed the Delaware River to Admiral Howe's efforts to resupply his brother. General Howe's conquest of Philadelphia did not produce the desired results he had hoped for. Unlike campaigns fought in Europe where the capture of the enemy's capital had devastating , political, economic, and psychological consequences, the capture of the American capital did not have the same impact on the fledgling country. Furthermore, with cold weather fast approaching and the accompanying freeze of the Delaware, it was imperative that the river forts be eliminated. Without control of the river, so vital as a supply and communication line, Howe and his besieged army would be forced to abandon the city or be starved into submission. During the next two months, Howe and Washington struggled for control of the Delaware. The three American forts, Mercer, Mifflin, and Billingsport, and the Pennsylvania navy, heroically battled the British, sinking two large warships, inflicting damage on many others, and defeating an assault by crack Hessian troops. Finally the forts began to fall. Billingsport, which guarded the first line of underwater obstructions known as chevaux-de-frise, was taken. Then on November 15th, after days of heavy bombardment by British land and naval artillery, Fort Mifflin's tenacious defenders were evacuated. Finally, on November 20th, as a large British force approached Fort Mercer, it too was abandoned and destroyed. The Pennsylvania navy, having lost the protection of the forts, made a valiant escape upriver past the Philadelphia shore batteries. Although many of the smaller galleys went undetected, the larger American ships were fired on and severely damaged. Rather than allowing them to fall into British hands, they were set on fire by their crews and destroyed. The British had broken the siege of Philadelphia and averted disaster. But it was a Pyrrhic victory. Howe had lost two warships, some of his best officers, and many troops. But perhaps more critical was the time lost. It had become impossible for him to assist Burgoyne who was defeated in October at Saratoga, New York. Howe set up winter quarters in the American capital while Washington's army camped at Valley Forge. The British strategy to end the war in 1777 had failed."