Volume 10 opens with Washington headquartered at the Continental army's encampment at Middlebrook, New Jersey, about seven miles northeast of New Brunswick, the location of the main British force under General William Howe. From this vantage point in the WaHChung Mountains, Washington could survey the country between Perth Amboy and New Brunswick while keeping an eye on the road to Philadelphia. Washington also considered the possibility that Howe might attempt to rendezvous his army with General Burgoyne's, thought to be en route from Quebec to Albany by way of Lake Champlain and the Hudson River.

For his part Howe, whose army outnumbered the Americans more than two to one, hoped to lure Washington away from his defensive positions and force a general engagement. When a series of British maneuvers in late June failed to bring on the desired fight, Howe evacuated his army from New Jersey to Staten Island, leaving Washington completely in the dark as to the enemy's next move and keenly aware of "the great advantage they derive from their navy." Although Howe had abandoned the idea of attacking the main Continental army, from his new disposition the British commander easily could join with Burgoyne via the Hudson, move upon the Philadelphia by way fot he Delaware river or the Chesapeake Bay, sail farther south into Virginia or to Charleston, South Carolina, or sail northward and invade one of the New England states.

Washington repositioned his army back at its old camp at Morristown, where it could better assist the American troops at Peekskill, New York, if Howe moved up the Hudson and yet still interfere with any British designs upon Philadelphia. Although surveillance reports revealed that the British were preparing for "a longer Voyage than up the North River," the British capture of Ticonderoga, New York, convinced Washington that Howe would take the northern route, and he swiftly marched the Continental army into New York State, where it remained until it became clear that the British fleet had gone out to sea. Washington then returned to New Jersey, where he made preparations to defend Philadelphia, but with several critical weeks of the summer campaign already passed, he confessed his puzzlement at his foe's decision to sail south.