Fortress on the Delaware
A pivotal confrontation in the American Revolutionary War for control of the vital Delaware River.
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The Siege Unveiled
A Critical Confrontation
The siege of Fort Mifflin, also known as the siege of Mud Island Fort, occurred from September 26 to November 16, 1777. This intense operation saw British forces, under the command of Captain John Montresor and Vice Admiral Lord Richard Howe, endeavor to capture the American fort situated in the Delaware River. The fort, commanded by Lieutenant Colonel Samuel Smith, ultimately fell after a prolonged and devastating bombardment, marking a significant British victory in the Philadelphia campaign.
Strategic Importance
Following the British occupation of Philadelphia on September 26, 1777, securing supply lines became paramount. Fort Mifflin, positioned on Mud Island, and Fort Mercer at Red Bank, New Jersey, along with river obstructions and Commodore John Hazelwood's flotilla, effectively blocked the Royal Navy from delivering provisions to the city. This blockade necessitated the siege to clear the river and sustain the British presence in the occupied capital.
Duration and Outcome
Lasting over a month and three weeks, the siege was characterized by fierce fighting, naval bombardments, and significant casualties on both sides. Despite determined American resistance, the relentless pressure from British artillery and naval forces eventually forced the evacuation of the fort, opening the Delaware River and ensuring the British could maintain their hold on Philadelphia until June 1778.
Setting the Stage
Post-Brandywine Landscape
Following their victory at the Battle of Brandywine on September 11, 1777, British General Sir William Howe occupied Philadelphia on September 26. The Continental Congress relocated to Lancaster, then York, Pennsylvania. The strategic objective for the British was to secure the Delaware River for resupply, a task complicated by the formidable defenses established by the Americans, including Fort Mifflin and Fort Mercer, supported by Commodore Hazelwood's river flotilla.
Fortifications and Engineers
The defenses at Fort Mifflin, initially designed by British engineer Captain John Montresor in 1771, were completed with earthen ramparts and wooden palisades after the war's outbreak. The river was further obstructed by chevaux de frise, underwater obstacles designed to damage enemy ships. The American efforts to bolster these defenses were marked by internal friction among French engineers, notably Philippe Charles Tronson du Coudray, whose untimely death left Louis Lebègue Duportail and others to refine the fortifications.
Early Engagements
The initial phase saw attempts to dislodge the American defenses. A Hessian assault on Fort Mercer on October 22, led by Colonel Carl von Donop, resulted in heavy losses for the attackers and was repulsed by the 1st Rhode Island Regiment under Colonel Christopher Greene. Concurrently, two British warships, HMS Augusta and HMS Merlin, ran aground while bombarding Fort Mifflin and were subsequently destroyed by American fire or self-immolation on October 23, a significant setback for the Royal Navy.
The Gauntlet
Preparations and Command
Fort Mifflin's garrison, initially composed of inexperienced militia, was reinforced with Continental soldiers under Lieutenant Colonel Samuel Smith. Despite command challenges, including the arrival of higher-ranking officers and the departure of a seemingly unfit Baron d'Arendt, Smith, later succeeded by Major Simeon Thayer, maintained the defense. French engineer Major François-Louis Teissèdre de Fleury significantly improved the fort's defenses, constructing firing steps, a redan, and a redoubt, bolstering the garrison's ability to withstand the escalating assault.
Environmental and Naval Pressure
A severe nor'easter storm in late October flooded the islands, temporarily halting direct combat but exacerbating the difficult conditions for both sides. The British, however, systematically increased their artillery presence, establishing new batteries and bringing specialized bombardment vessels like HMS Vigilant into position. This overwhelming firepower began to systematically dismantle the fort's structures.
The Final Bombardment
By November 10, the British had amassed a formidable artillery park. The fort endured relentless bombardment, with cannonballs smashing through barracks and palisades. Despite valiant efforts by the defenders to repair damage, the fort's defenses were critically weakened. On November 15, the heavily armed HMS Vigilant moved into close range, delivering devastating point-blank fire. The intense barrage, coupled with mounting casualties and the destruction of fortifications, rendered the fort untenable.
Evacuation
Under the command of Major Simeon Thayer, the surviving defenders, numbering around 300, were evacuated across the Delaware River on the night of November 15. A small detail remained to set fire to the barracks before joining the others. The fort was left flying its flag, a symbol of defiance, until the morning of November 16, when British marines lowered it and took possession of the ruined fortifications.
Consequences and Consolidation
Opening the River
The fall of Fort Mifflin, followed by the abandonment of Fort Mercer on November 20, effectively cleared the Delaware River of American obstructions and naval presence. Commodore Hazelwood ordered his ships scuttled to prevent their capture. This strategic victory allowed the Royal Navy unimpeded access to Philadelphia, ensuring the British garrison could be adequately supplied throughout the winter occupation.
American Losses
The defense of Fort Mifflin, though ultimately unsuccessful, inflicted significant casualties on the British and Royal Navy, including the destruction of two warships. The American garrison suffered approximately 250 killed and wounded from an initial strength of around 450 men plus reinforcements. The resilience shown by the defenders, despite overwhelming odds and horrific conditions, earned grudging respect from their adversaries.
Subsequent Actions
With the river secured, the British consolidated their position in Philadelphia. The strategic importance of the forts was underscored by subsequent actions, such as the Battle of Gloucester on November 25, as British forces withdrew from New Jersey. The successful siege was a critical step in the British strategy during the Philadelphia campaign, impacting the broader course of the Revolutionary War.
Historical Notes
Key Figures and Units
The siege involved prominent figures such as Lieutenant Colonel Samuel Smith, Major Simeon Thayer, Major François-Louis Teissèdre de Fleury, and Commodore John Hazelwood for the American forces. British command included Captain John Montresor and Vice Admiral Lord Richard Howe. Notable American units included the 1st and 2nd Rhode Island Regiments, elements of the 4th Maryland Regiment, and the 4th and 8th Connecticut Regiments, alongside the Pennsylvania Navy.
Naval Aspects
The Royal Navy's role was crucial, involving ships of the line like HMS Augusta and frigates, alongside specialized vessels like the converted bombardment ship HMS Vigilant. The American river flotilla, under Commodore Hazelwood, played a vital defensive role, employing galleys and employing tactics like river obstructions (chevaux de frise) and nighttime supply runs to counter British naval superiority.
Casualties and Impact
While precise figures vary, American casualties are estimated around 250 killed and wounded. British losses in the final assault phase were minimal, but the overall campaign effort was substantial. The successful capture of Fort Mifflin was instrumental in securing Philadelphia for the British, impacting the strategic momentum of the war during that period.
Sources
Primary and Secondary Accounts
The historical narrative of the Siege of Fort Mifflin is drawn from a range of scholarly works and primary sources:
- Boatner, Mark M. III. Encyclopedia of the American Revolution. Stackpole Books, 1994.
- Dorwart, Jeffrey M. Fort Mifflin of Philadelphia. University of Pennsylvania Press, 1998.
- Dupuy, R. Ernest, and Trevor N. Dupuy. The Encyclopedia of Military History. Harper & Row, 1977.
- Eggenberger, David. An Encyclopedia of Battles. Dover Publications, 1985.
- Heitman, Francis Bernard. Historical Register of Officers of the Continental Army during the War of the Revolution. Rare Book Shop Publishing Company, 1914.
- Jackson, John. Fort Mifflin: Valiant Defender of the Delaware. James & Sons, 1986.
- Jackson, John. The Pennsylvania Navy, 1775-1781. Rutgers University Press.
- Martin, Joseph Plum. Private Yankee Doodle. Western Acorn Press, 1962.
- McGuire, Thomas J. The Philadelphia Campaign, Volume II. Stackpole Books, 2007.
- Massachusetts, Secretary of the Commonwealth. Massachusetts Soldiers and Sailors in the War of the Revolution. Wright and Potter Printing Co., 1907.
- Phillips, Michael. "AUGUSTA (64) 4th Rate". ageofnelson.org.
- Syrett, David. "H.M. Armed Ship Vigilant". Mariner's Mirror, vol. 64, no. 1, 1978, pp. 57-62.
- Thayer, Simeon, and Edwin Martin Stone (ed.). The Invasion of Canada in 1775: Including the Journal of Captain Simeon Thayer... Rhode Island Historical Society, 1867.
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References
References
- IHA, Valley Forge. Varnum's Brigade comprised the 1st and 2nd Rhode Island and the 4th and 8th Connecticut.
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