The campaign to seize Philadelphia, the second mayor phase of British strategy in 1777, began in late July. Some 15,000 troops under Howe's command sailed from New York on July 23 and landed at Head of Elk, Maryland, a month later on August 25. Gen. George Washington, with about 11,000 men, took up a defensive position blocking the way to Philadelphia at Chad's Ford on the eastern side of Brandywine Creek in Pennsylvania. Gen. William Howe attacked on September 11, sending Gen. Charles Cornwallis across the creek in a wide-sweeping flanking movement around the American right, while his Hessian troops demonstrated opposite Chad's Ford. Maj. Gen. Nathanael Greene's troops staved off Cornwallis' threatened envelopment of Washington's whole force, and the Americans fell back to Chester in a hard-pressed but orderly retreat. Patriot losses in this engagement totaled about 1,000 killed, wounded, and prisoners. British casualties were less than 600.
After their victory at the Battle of Brandywine, the British forces under Howe maneuvered in the vicinity of Philadelphia for two weeks, virtually annihilating a rear guard force under Brig. Gen. Anthony Wayne at Paoli on September 21, 1777, before moving unopposed into the city on September 26. Howe established his main encampment in nearby Germantown, stationing some 9,000 men there. Washington promptly attempted a coordinated attack against this garrison on the night of October 3-4. Columns were to move into Germantown from 4 different directions and begin the assault at dawn. Two of the columns, both made up of militia, never appeared to take part in the attack, but in the early phases of the fighting the columns under Greene and Divan achieved considerable success.
However, a dense early morning fog which resulted in some American troops firing on each other while it permitted the better disciplined British to re-form for a counterattack and a shortage of, ammunition contributed to the still not fully explained retreat of the Americans, beginning about 9:00 A.M. Howe pursued the Colonials a few miles as they fell back in disorder, but he did not exploit his victory.