Shortly after the Army of Northern Virginia won a major victory over the Army of the Potomac at the Battle of Chancellorsville (April 30 – May 6, 1863), General Robert E. Lee decided upon a second invasion of the North (the first was the unsuccessful Maryland campaign of September 1862, which ended in the bloody Battle of Antietam). Such a move would upset the Union's plans for the summer campaigning season and possibly reduce the pressure on the besieged Confederate garrison at Vicksburg. The invasion would allow the Confederates to live off the bounty of the rich Northern farms while giving war-ravaged Virginia a much-needed rest. In addition, Lee's 72,000-man army^[1] could threaten Philadelphia, Baltimore, and Washington, and possibly strengthen the growing peace movement in the North.^[2]