Robert E. Lee decides in June 1863 to capitalize on his victory at Chancellorsville by repeating his strategy of 1862 and once again invading the North.

He does this to resupply his army, give the farmers of Virginia a respite from war, and threaten the morale of Northern civilians, possibly by seizing an important northern city, such as Harrisburg, Pennsylvania, or Baltimore, Maryland.

The Confederate government agrees to this strategy only reluctantly because Jefferson Davis is concerned about the fate of Vicksburg, Mississippi, the river fortress being threatened by Ulysses S. Grant's Vicksburg campaign.

Following the death of Jackson, Lee has organized the Army of Northern Virginia into three corps, led by Lieutenant Generals James Longstreet, Richard S. Ewell, and A.P. Hill.