A War of Posts
Over eight years of struggle, the American Revolutionary War shifted from guerrilla warfare to limited battles, and sometimes to maneuver warfare. However, the demands of 18th-century fighting across a vast area filled with rough terrain, dense forests, and uncooperative rivers made it almost always a war of posts. A war of posts is similar to a chess match, with carefully placed defensive positions designed to protect supply lines, stop an enemy advance, and control vital regions.
Think of the game, Risk, but with real people, sweat, and effort, not small wooden or plastic pieces. The fight for North America included several key battles featuring fixed fortifications. In many ways, these defined the war: West Point and Ticonderoga immediately come to mind. But many battles also involved temporary or hastily constructed forts. These were just as important. Fort Moultrie, Stony Point, and Yorktown serve as notable examples.
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| Fort Ticonderoga |
The Siege
The war featured several key sieges. Most were short-lived, with one side surrendering or the other breaking off the siege due to outside factors like weather, supplies, or reinforcements. Fort Stanwix, Savannah, Charleston, and Newport are examples. Even a brief defense of a position could buy crucial time for a commander to gather forces, regroup, maneuver for advantage, or simply escape.
That’s why, when a commander faced a long siege or was forced to storm a position, they often treated the defenders and any civilians left behind harshly. Ironically, when the British treated defenders roughly, it fueled rebel propaganda, which played a significant role in the conflict. Not only was the American public watching closely, but the whole world was paying attention. That’s a topic for another post, however.
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| Fort Stanwix |
Fort Mifflin
Arguably, the longest active defense of a post under siege in the war was also one of the least celebrated. We will try to shift the focus toward celebration. Fort Mifflin is located on the Delaware River, in what is now South Philadelphia, at a place called Mud Island. Construction on the fort began in 1772 to block access to the city.
Ironically, the original construction was overseen by the famous British engineer Captain John Montressor. The fort was completed in 1777 under the leadership of American Major General Thomas Mifflin, for whom it is named. It protected a series of water barriers that stretched across the river to its sister fort, Fort Mercer, in New Jersey.
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| Maj Gen Thomas Mifflin finished construction of the fort that bears his name |
Most Formidable Defenses
A fort guarding a sea approach needed more than just strong walls and good firing positions. So, Philadelphia built a series of chevaux de frise, placed in "tiers" beneath the waters of the Delaware between Forts Mercer and Mifflin. They were constructed within wooden-framed boxes, 30 feet square, made from massive timbers lined with pine boards. The engineers sunk these frames into the riverbed.
Each box was filled with 20 to 40 tons of stone to keep it in place. Each frame had two or three large timbers tipped with iron spikes set underwater and angled downstream. These chevaux created a tough obstacle that could trap unwary ships. The chain of chevaux had gaps so friendly shipping could pass through. The locations of these safe passages were tightly kept secret. Any British ship not caught on the spikes or caught in the chain still faced fire from the forts themselves.
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| Sketch of chevaux crates filled with stones |
A Strategic Position
The British captured Philadelphia in September 1777 through an overland campaign that avoided the fortified Delaware approach. However, the British commander in chief, General William Howe, now faced the urgency of establishing a communication line to the sea. He needed the protection of the Royal Navy and an open supply route, or his position in Philadelphia could become a liability.
The British commander recognized that their control of the sea was an invaluable advantage over the Americans, which had to be leveraged to the fullest. Howe's brother, Admiral Richard "Black Dick" Howe, commander of the Royal Navy in America, had already started weakening American defenses downriver. But brother Billy couldn't wait for their arrival; he needed to advance overland against Fort Mifflin and hold the navy at Fort Mercer on the Jersey side.
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| Control of the lower Delaware River and bay was crucial to British success |
Doughty Defenders
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| Samuel Smith |
But the American commander in chief, General George Washington, also recognized the importance of the Delaware. After being driven from near the capital following his defeat at Germantown, Washington prepared for a lengthy series of operations aimed at disrupting British efforts to strengthen their control over Philadelphia.
On September 23, Washington sent Lieutenant Colonel Samuel Smith of the 4th Maryland Regiment with a detachment of Continentals to the fort on Mud Island in the Delaware River.
Readers may recall I featured this first patriot in an earlier Yankee Doodle Spies post. Smith's initial force numbered 200 soldiers, along with Major Robert Ballard of Virginia, Major Simeon Thayer of Rhode Island, and Captain Samuel Treat of the Continental Artillery. Determined to hinder British plans at any cost, the Continentals began preparing defenses and calling in more troops.
Eventually, they would have 400 men, which was far from enough to properly garrison a fort of Mifflin's size. This problem was similar to issues faced by other forces trying to hold forts Ticonderoga and Washington. Still, Smith and his men chose to make the best of the fort.
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| Fort Mifflin plans |
The British Approach
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| John Montressor |
General Howe ordered a move against nearby Providence Island on October 10, 1777. Washington's land forces resisted but were quickly driven off, and soon heavy siege guns were positioned to face the American fort. Despite its strength, Fort Mifflin had not been heavily fortified against a threat from Philadelphia.
Ironically, Captain John Montresor, who had designed and built Fort Mifflin, planned and constructed the siege works used against his own fort. The situation was certainly against the rebels. Soon, heavy cannonballs started crashing into the American positions. The intense pounding on that side of the fort was horrific, but the Americans fought valiantly, inflicting heavy damage on several British ships attempting to bypass upriver.
The British mounted guns on floats, creating water batteries that moved closer to the besieged outpost. American casualties increased, and supplies dwindled during the month of relentless bombardment and hardship.
The Royal Navy Engages
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| "Black Dick" Howe - so named for a swarthy complexion |
But Billie Howe's brother, "Black Dick," would have the final say. He finally managed to unleash the Royal Navy. On November 10, a floating battery with twenty-two heavy 24-pound guns came within 40 yards of the fort.
At close range, the British gunners could do as much damage as they wanted. This ended up being the heaviest bombardment of the Revolutionary War. Shot and shell shattered walls and buildings. The defenders suffered severe injuries, with limbs torn away or crushed.
The battle was leaning towards the besiegers, but Smith and the defenders were determined to hold the fort. Cold weather was arriving early, and if they could hold until the Delaware froze, the British supply line might be cut, forcing Howe's army to abandon the recently captured capital.
On the British side, news of Major General John Burgoyne's army’s disastrous surrender at Saratoga increased pressure on both Howe brothers. A victory over the stubborn defenders could help boost the sagging morale. The stakes were high for both sides!
The Pennsylvania Navy (yes, they had a navy) came to the aid of the forts guarding the Delaware approaches. Commodore John Hazelwood, with a sizable fleet of galleys, sloops, and fire-vessels, launched several raids on British positions onshore and constantly harassed British river operations while patrolling the waters around the fort. But British naval strength eventually prevailed. Rebel resistance persisted. Cold, ill, and starving, the garrison, reduced to much less than 200 of the original 400-450 men, refused to surrender.
Under the leadership of French Major Francois de Fleury, an engineer of remarkable energy, the Americans worked each night to repair the damage from the day’s combat. Fleury himself was wounded in the battle. A British ship of the line and sloop-of-war both ran aground under heavy fire from Mifflin's defenders. However, British naval superiority virtually guaranteed an unfavorable outcome. Behind the cover of the intense fire from the big guns of the floating battery, the British naval vessels closed in, and soon British marines were sniping at the fort from high in the rigging. With nearly all their guns knocked out, the Americans were running out of options - but not out of spirit.
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| Fort Mifflin, aka Mudd Island was the key to the Delaware |
The Final British Assault
Clear weather on November 15 gave the British a chance to deliver a final burst of heat. They sent two ships, Vigilant and Fury, armed with nineteen guns, along the backchannel west of Fort Mifflin. At the same time, three large ships with 158 cannons anchored directly off the fort, in the main channel of the Delaware. To the east, three more vessels with about 51 guns guarded Mifflin from all sides. A trap of smoke, fire, and iron.
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| The Royal Navy had to commit massive resources to subdue the fort |
To oppose this British juggernaut, the defenders of Fort Mifflin had only ten cannons remaining. Soon, hundreds of cannonballs began pummeling what was left of the fort. The large-caliber 18- and 24-pound balls tore through the defenders in another burst of smoke and fire. During the peak of the bombardment, about 1000 shots were fired into the fort.
To worsen the defenders' plight, British Marines climbed to the crow’s nest of Vigilant and tossed grenades at the fort's defenders. The defenders fought bravely but suffered for it as casualties increased. They returned fire until all their guns were silenced by the heavier British shot. Lieutenant Colonel Smith was seriously wounded and had to be evacuated. The end was near.
The End
Nightfall found the surviving defenders exhausted, cold, and out of ammunition. But not out of options. The new commander of the fort, Major Simeon Thayer, decided to evacuate the now indefensible Mifflin under the cover of darkness. The garrison rowed their way with muffled oars to Fort Mercer. Forty men volunteered to stay behind and set fire to what was left.
Their work done, around midnight, they also crossed the Delaware to the safety of New Jersey. But Thayer decided on one last act of resistance. So as the last of Mifflin's valiant defenders rowed to safety, they would see it ablaze - but they would see the flag still flying in a final gesture of defiance.
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| The unusual-looking flag that flew over Fort Mifflin during the long siege, and in a final act of defiance |
The Result
During the siege, about 400 American soldiers held off more than two thousand British troops and 250 ships. The Americans suffered over 250 killed and wounded and lost the fort. However, the time and resources spent by the Howe brothers to capture the fort and control the Delaware allowed Washington to move his army to White Marsh and ultimately reach the safety of winter quarters at Valley Forge, where a new American army was formed.
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| A new American army would emerge from the hard winter at Valley Forge |
Aftermath
Fort Mifflin was rebuilt after the war and served as a U.S. base for many years, providing one of the strategic harbor defenses for Philadelphia. Later, it became a historic site. Today, only the white stone walls of the original Fort Mifflin remain. The pockmarks in these walls testify to the intensity of the British bombardment in 1777. Local residents refer to this siege and bombardment as the Battle of Mud Island. However, this once-critical fort in the defense of the Delaware and Philadelphia never saw military use again.
