As early as the 9th two new departments had been created for Pennsylvania: That of the Monongahela, with headquarters at Pittsburg, was assigned to Major-General W.T.H.
Brooks; and that of the Susquehanna, with headquarters at Carlisle, to Major-General Darius N.Couch.
On the 15th Ewell reached Williamsport with a force estimated at twelve thousand men and sixteen guns.
Before Couch could reach Carlisle it was already occupied by Jenkins' cavalry, and the terrified farmers of that section of country were fleeing in crowds across the Susquehanna, driving their horses and cattle before them..