One in an occasional series

Cannons boom on the Delaware River.

Hour after hour, day after day, British artillery on land and on ship have pounded Fort Mifflin, hunched over on its muddy little island in the river just off the Pennsylvania shore.

Inside the fort, American soldiers - cold, wet, sleepless and hungry - hang on defiantly, keeping British ships from getting to Philadelphia with supplies badly needed by the redcoat army occupying the city.

The date is Nov. 15, 1777. The British have been trying for the better part of two months to break the American blockade of the river. Now they are concentrating on Fort Mifflin, the key to the defensive screen the Americans have thrown across the Delaware just south of Philadelphia.

The British have been firing their cannons at Fort Mifflin since Oct. 15, but on Nov. 10, they intensify the attack, beginning a round-the-clock bombardment. At times, the British fire as many as 1,000 cannonballs in 20 minutes.

After several days, the British batteries silence nearly every piece of artillery at Fort Mifflin. "Our men were cut up like cornstalks... ," Joseph Plumb Martin, a teenage Connecticut soldier who was there, recalls years later. "The whole area of the fort was as completely plowed as a field... . If ever destruction was complete, it was here."

Off to the northwest of the city at Whitemarsh, American commander-in-chief George Washington and his ill-shod army can only wait helplessly, out of position to launch an attack that would break the siege.

On the night of Nov. 15, the American garrison bows to the inevitable and abandons Fort Mifflin, leaving the dead behind and the flag flying. Of the 450 defenders, 250 are casualties.

Across the river at Red Bank (now National Park) on the New Jersey side, Fort Mercer, the last American stronghold on the Delaware, hangs on for another five days before Continental forces abandon it on the night of Nov. 21. A few small British ships arrive in Philadelphia the very next day, to be followed soon by other, larger vessels.

The British at last have their water route and a free flow of supplies to Philadelphia, but the stubborn American resistance has tied up the redcoats for nearly seven weeks, allowing Washington to regroup after the hard fighting and marching of late summer and early fall.

• 

The capture of Philadelphia is at the heart of Gen. Sir William Howe's plan to end the American rebellion. Howe believes that seizing the capital of the rebellion will unleash a tide of loyalist sentiment, fatally weakening the Revolution.

So far, though, there is no sign of a great loyalist uprising, even though Pennsylvanians - to the disgust especially of New Englanders serving in Congress and the Continental Army - have not rushed in great numbers to join the militia and help Washington toss out the invaders.

And far to the north, a British army under Gen. John Burgoyne has surrendered to American forces under Gen. Horatio Gates at Saratoga on Oct. 17.

The loyalists in New York did not rise to Burgoyne's aid any more than Pennsylvania loyalists have rallied to Howe.

If the British are to suppress the rebellion, they will have to do it without much American help.

• 

Howe landed his army of about 16,000 British and German soldiers on Aug. 25 near Head of Elk, Md., after a sea voyage from Sandy Hook, N. J., that took a month because of storms that blew some of the ships all the way to Ireland and because of concerns about the defenses on the Delaware.

Once Howe's troops had recovered from their long shipboard confinement, they defeated the Americans at the Battle of the Brandywine on Sept. 11, outmaneuvered Washington's army in Chester County, and occupied Philadelphia on Sept. 26. Then, on Oct. 4, the British repelled a daring American attack at Germantown. Since then, Howe has concentrated on the urgent task of opening the Delaware.

Seizing Philadelphia is one thing; surviving there, between two rivers, is another. If the British can't bring their fleet upriver, Howe's army may find itself trapped in Philadelphia for the winter with virtually no supplies, and Washington's army at the door.

For the moment, the British can sneak supplies upriver at night in flat-bottom boats that hug the shore. Or they can send provisions overland from the lower Delaware, where the British fleet rides at anchor.

But the flat bottoms are at risk from American gunboats, and the land route between Chester and Philadelphia is subject to attack by marauding Continental army patrols. "Washington is making the route by land very unsafe between Chester and Philadelphia," Capt. Johann Ewald, a Hessian mercenary, writes in his diary on Nov. 6. "The greater part of the provision still must be brought through the dangerous passage by water."

• 

The American defenses of the Delaware, which begin just below the city, are formidable.

Hidden beneath the water's surface, waiting to rip open the hulls of British ships, is a series of obstacles called chevaux-de-frise: long, thick stakes tipped with an iron point and anchored in large wooden boxes weighted with stones and sunk to the bottom of the river.

While the chevaux-de-frise guard the river, three fortifications guard the chevaux-de-frise. The northernmost is Fort Mercer, on the Jersey shore across from the mouth of the Schuylkill. Next comes Fort Mifflin, right below the mouth of the Schuylkill on the Pennsylvania side. The southernmost is Billingsport, on the Jersey side about four miles south of Fort Mercer.

Supporting the forts is a flotilla of about 50 vessels from the Continental and Pennsylvania navies.

The British begin their campaign with an assault on Billingsport and Fort Mercer.

Billingsport falls easily enough on Oct. 2, but Fort Mercer is another matter.

Howe dispatches a force of about 1,800 Hessian mercenaries under the supremely egotistical Count Karl von Donop to seize Fort Mercer, which has a garrison of only about 400.

The Hessians, looking to redeem themselves for their embarrassing defeat at Trenton the previous Christmas, arrive at the fort on Oct. 22 expecting an easy victory. But in a fierce 45-minute fight, the American defenders maul the attacking Hessians. More than 400 German soldiers are killed or wounded. Donop himself suffers a fatal wound, observing before he expires several days later that he is "finishing a noble career early."

Rushing to aid the Hessian attack, the man of war Augusta, with 64 guns, and a much smaller vessel, the 18-gun Merlin, run aground. The American forts bombard them the next day, and the Augusta - by now abandoned - blows up with an explosion that can be heard in Reading and shatters glass in Philadelphia. The Merlin also goes up, but less spectacularly.

After the Fort Mercer fiasco, an impatient Howe ratchets up the pressure on Fort Mifflin.

The fort itself is only partially completed when the siege begins, making it difficult to defend.

The east and south walls, facing the river, are granite, but the north and west walls, facing the land, are palisades and packed dirt. After the British cannons battered the walls all day, the Americans would scramble to rebuild them at night.

The Americans put up a valiant defense, even managing to silence a British battery, but they are outmanned and outgunned.

Redcoat firepower turns the fort into a killing ground, with almost nowhere to hide.

"I saw men who were stooping to be protected by the works, but not stooping low enough, split like fish to be broiled," recalls Joseph Plumb Martin.

By Nov. 15, it is clearly time to go. The defenders "set fire to every thing that would burn, and then repaired immediately to the wharf where three bateaux were waiting to convey us across the river," Martin remembers.

The siege of Fort Mifflin is over. Soon, Howe will be free to turn his attention once more to destroying Washington.

Next time: Howe on the move