One in a series of articles recounting Philadelphia's days in the Revolutionary War.

The American rebellion against King George III must be over. Why else would the British army be throwing such a party?

The date is May 18, 1778, a Monday.

Galleys and barges, warships and transports, all decorated with flying streamers, crowd the Delaware River as if to celebrate a great victory.

Ashore, in a spectacle unlike anything Quaker Philadelphia has ever seen, knights in red and white silk joust in honor of fair ladies - seven daughters of Philadelphia's finest families, wearing towering bejeweled headdresses and flowing white silk robes with spangled sashes.

After the tournament come fireworks, midnight dining, and dancing that lasts nearly until dawn in a ballroom lined with 85 mirrors.

The whole outrageous thing is called a mischianza, or medley, so named because it includes several kinds of revelry.

But this extravaganza is no triumph. It is a feverish farewell to Sir William Howe, commander-in-chief of the British army that has occupied Philadelphia since last fall. The bash is bankrolled by 22 of Howe's officers and orchestrated by Capt. John Andre, an aide to one of Howe's generals.

Howe, who staked his strategy for ending the American rebellion on capturing Philadelphia, is going home to explain himself - and seek vindication for his policies - at a time when the insurrection he was supposed to quell has just been invigorated by the promise of aid from England's ancient enemy, France.

And with a French fleet on the way, Howe is not the only one leaving. As Howe informs one worried Loyalist, "it was probable, on Account of the French War, the [British] Troops would be withdrawn [from Philadelphia]."

The British have decided to abandon Philadelphia rather than risk being trapped there, 60 miles upriver from the sea, with French ships blocking access to the ocean.

But that's not the only reason the British are leaving. France's entry into the war also means that the conflict has expanded to other parts of the world. The British are now looking to the Caribbean, where they must defend their own colonies but also have the chance to capture a few French possessions. Fighting for the West Indies is more important to London than holding Philadelphia.

Howe's successor, Sir Henry Clinton, will send some of his troops to the West Indies and move the main army to New York, a more advantageous location for responding to French operations.

None of this is a comfort to Philadelphia's Tories, who are advised by Howe to make their own peace with the rebels.

Loyalists such as former Pennsylvania Assembly Speaker Joseph Galloway, who had been a member of the First Continental Congress but could not stomach independence, are devastated by the prospect of a British evacuation.

Ambrose Serle, a British official with close ties to the Loyalists of Philadelphia, writes in his journal on May 23 that "... nothing but misery & Sorrow are to be seen in the Town."

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The winter of 1777-78 brought a reversal of fortunes to the British and Continental Armies that would have been hard to predict when the weary, hungry, ill-shod Americans limped into Valley Forge while the British made themselves at home in Philadelphia.

Howe and his American counterpart, George Washington, have run into political sniping in recent months. Washington has survived it; Howe has not.

Some politicians in London have grumbled that Howe, known as a friend to the colonies before the Revolution, has not been aggressive enough.

Even though Howe's Redcoats pushed the Americans around Southeastern Pennsylvania last fall before taking Philadelphia, Howe failed to pursue and destroy the Continental Army - to the chagrin of some of his officers.

The ability of Washington's army to take on the British and survive, coupled with the American defeat of a British army under Gen. John Burgoyne at Saratoga in northern New York last fall, persuaded a cautious French government to back American independence.

Howe, who believes the ministry has not given him the resources he needs, turned in his resignation last fall, but word that it was accepted did not reach America until last month.

A Parliamentary investigation of Howe's conduct will end inconclusively, but the king apparently does not blame Howe for failing to crush the rebellion, for the general's military career continues to flourish.

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While Howe is packing his bags, the Continental Army, drilled into efficiency by Friedrich von Steuben and fortified by the promise of French help, has emerged from its miserable winter at Valley Forge in high spirits.

As the British officers dance the night away at the mischianza, American troops stage a hit-and-run raid against the British line of defense.

Earlier in the day, in an even more provocative move, the Marquis de Lafayette leads a force of about 3,000 men to Barren Hill, northwest of Philadelphia, under orders from Washington "to move between the Delaware and Schuylkill, for restraining the Enemy's [foraging] parties, procuring intelligence and to act as circumstances may require."

On the night of May 19, a British detachment marches quickly out of the city and circles behind Lafayette's troops, but the Americans, as Washington reports to Congress on May 24, make "a timely and handsome retreat in great order over the Schuylkill at Matsons ford. Our loss was nine men in the whole."

Once across the Schuylkill, the Americans turn and wait for the British to attack, recalls Joseph Plumb Martin, a teenage Continental soldier from Connecticut.

But the alarm has been sounded at nearby Valley Forge "and the whole army was immediately in motion," Martin recalls in his memoirs. "The British fearing that they should be outnumbered in their turn, directly set their faces for Philadelphia and set off in as much or more haste than we had left Barren hill."

It is the last time Sir William Howe will send troops into battle against the Americans. On Sunday, May 24, 1778, he boards a transport and sails out of American history.