The American Revolutionary War saw Philadelphia, the seat of the Second Continental Congress, become a prime target for British forces in 1777. The British Philadelphia campaign aimed to capture this vital
city, prompting significant defensive efforts from the Continental Army. Despite General William Howe's strategic maneuvers and eventual capture of the city, American forces, particularly at key strongholds like Fort Mifflin, mounted a determined resistance that complicated British supply lines and demonstrated the resilience of the nascent nation.
Washington's Strategic Positioning and Early Skirmishes
Following earlier engagements and an uneasy stalemate, General George Washington's Continental Army was primarily encamped at Morristown, New Jersey. A forward base at Bound Brook, close to British outposts, was a point of contention. In April 1777, General Charles Cornwallis led a British raid against this position, nearly capturing its commander, Benjamin Lincoln. This incident prompted Washington to strategically relocate his army to a strongly fortified position at Middlebrook in the Watchung Mountains. This location was chosen because it commanded likely British land routes toward Philadelphia, allowing Washington to monitor and potentially intercept any overland advance.
Howe's initial movements were often deceptive. He moved a substantial army to Somerset Court House, south of New Brunswick, New Jersey, in what appeared to be a feint to draw Washington out from his strong position. However, Washington, having intelligence that Howe lacked the necessary watercraft for a Delaware River crossing, did not commit his main force. When Howe eventually withdrew his army back toward Perth Amboy, Washington followed. This led to a swift strike where Howe sent forces under Cornwallis to cut Washington off from high ground, an attempt that was foiled in the Battle of Short Hills. After these maneuvers, Howe withdrew his troops, embarked them on transports, and sailed out of New York harbor, leaving Washington uncertain of his true destination.
The Critical Role of Fort Mifflin in Delaying British Supply
Once Howe's fleet entered Chesapeake Bay, Washington began moving his troops south to prepare Philadelphia's defenses. A crucial element of this defense was Fort Mifflin, located on Mud Island in the Delaware River. The fort played a vital role in blocking British supply convoys from reaching Philadelphia by river, effectively creating a blockade that caused shortages of food, rum, clothing, and money for Howe's troops in the captured city. The British were forced to send supplies via convoys of flatboats, which had to attempt passage at night and maintain total silence to avoid the guns of Fort Mifflin and the Pennsylvania Navy. Hessian Captain Johann von Ewald noted that sailors were made completely drunk to compel them to undertake this dangerous work.
On October 14, French engineer Major François-Louis Teissèdre de Fleury arrived at Fort Mifflin and significantly improved its defenses. He constructed a firing step, a redan to support the main battery, and a last-stand redoubt at the fort's center, addressing some of its shortcomings. Thomas Paine, who visited the fort on October 15, observed 30 enemy shells falling into the fort that day. The Americans also denied the British use of Province and Carpenter's Islands by breaking riverside dikes, forcing the British to build batteries on dikes and work in knee-deep water. This led to incidents like the loss of an 8-inch howitzer and a soldier drowning when its transport sank in the Schuylkill. On October 10, Captain John Montresor began constructing a battery on Carpenter's Island, which the Americans attacked, capturing two officers and 56 enlisted men.
The Siege and Fall of Fort Mifflin
The siege of Fort Mifflin intensified with naval bombardments. On October 23, American forts concentrated fire on two British ships, HMS Augusta and HMS Merlin, which had run aground. British accounts claimed American gunnery caused only slight damage, but flaming wads from the ships' own guns set Augusta on fire. Americans, however, asserted a lucky hit from Fort Mifflin's red-hot shot or a fire ship started the blaze. Augusta subsequently exploded in a tremendous blast, heard nearly 30 miles away, killing 60 sailors, a lieutenant, and the ship's chaplain. Merlin was then set on fire and also exploded. Despite this success, the British continued their assault.
By November 10, the British had assembled a formidable array of artillery, including 32-pounder, 24-pounder, and 18-pounder cannons, along with howitzers and mortars. They began a heavy bombardment, wrecking large parts of the palisades. On November 11, Captain Treat was killed, and the fort's commander, Smith, was severely wounded. The constant barrage took a heavy toll on the men, and Fleury reported that all but two guns were dismounted, though soldiers repaired damage nightly. On November 15, the British brought HMS Vigilant, a converted transport armed with 24-pounder cannons and sharpshooters, to within 20 yards of the fort, unleashing devastating point-blank fire. A single shot killed five American gunners. Despite the heroic efforts of the defenders, including Major Thayer who took command, the fort was overwhelmed. On the night of November 15, Thayer ordered the abandonment of Fort Mifflin. The 300 survivors and salvageable equipment were rowed to Red Bank, with a detail of 40 men burning the barracks before joining the others, marking the end of a valiant but ultimately unsuccessful defense.
