Shortly after General Robert E. Lee's Army of Northern Virginia won a smashing victory over the Federal Army of the Potomac at the Battle of Chancellorsville (May 1-3, 1863), Lee decided upon a second invasion of the north. Such a move would upset Federal plans for the summer campaigning season and possibly relieve the beseiged garrison at Vicksburg, and it would allow the Confederates to live off the bounty of the rich northern farms while giving war-raveged Virginia a much needed rest. Also, Lee's 75,000-man army could threaten Philadelphia, Baltimore, and Washington and give voice to the growing peace movement in the north.