Following the conclusion of the Gettysburg Campaign, the Confederate Army of Northern Virginia and Union Army of the Potomac regrouped on their previous positions astride opposite banks of the Rapidan River. For the duration of the summer both armies remained inactive, reorganizing and resupplying after the devastation wrought at Gettysburg. In early September, Lt. Gen. James Longstreet was dispatched with two divisions to aid the Confederate war effort in the West. After the Confederate victory at Chickamauga, which Longstreet helped secure, Maj. Gen. George Meade was forced to send the XI and XII Corps to help secure Middle Tennessee. When Gen. Robert E. Lee learned of the reassignment of the two Union Corps he decided to go on the offensive and force the Army of the Potomac to give battle on ground of his choosing.