In the fall of 1777, the British under General William Howe occupied Philadelphia and while the British spent a comfortable and enjoyable winter season there, General Washington and his troops endured dreadful deprivations at Valley Forge. When General Howe resigned his command in 1778, Captain John André and John Montresor orchestrated a spectacular farewell for him called the Meschianza (Italian for medley or mixture) that included a regatta, a procession, a joust of pretend knights, a ball, and fireworks. Prominently featured in the festivities were several of the city’s fashionable young ladies, Peggy Shippen, Rebecca Franks, daughter of loyalist David Franks, and Peggy Chew, daughter of Benjamin Chew among them.
Howe’s replacement, General Sir Henry Clinton, decided later in 1778 to withdraw from Philadelphia and consolidate the British position in New York City in expectation of a possible attack by American and French troops (France had signed a treaty with the United States in 1778).
Those who had fled Philadelphia returned to reclaim their city. General Benedict Arnold was in charge of the American forces there and it wasn’t long before the social calendar was full once again. MARY WHITE MORRIS (See previous posts here, here, here, here, and here.) wrote to her mother, Esther Hewlings White on 10 November 1778:

. . . I know of no News, Unless to tell you that we are very gay, as such, we have a great many Balls and Entertainments and Soon, the Assembly will begin, tell Mr. Hall Even our military Gentlemen here, are too Liberal to make any Distinctions between Wig and Tory Ladyes, if they make any, Its in favor of the latter, such, Strange as it may seem, is the way those things are Conducted at present in this City, it Originates at Headquarters, and that I may make some Apology for such Strange Conduct, I must tell you that Cupit has given our little General a more Mortal wound, than all the Host of Britons cou’d, unless His present Conduct can Expiate, for His past, — Miss Peggy Shippen is the fair One . . .
Mary Morris

The “little General” is, of course, Benedict Arnold.

The letter is in the Robert Morris Collection at the Huntington Library, Lists No. 5, pages 53-55, transcribed by Louise North. [Microfilm, courtesy of Dr. Elizabeth Nuxoll] The illustration is a sketch made by Captain André of a costume he proposed for the ladies participating in the celebration, from John Fanning Watson, Extra-Illustrated Manuscript of the Annals of Philadelphia (1830) and can be found HERE.