On 4th May, 1862, George McClellan moved his troops into the Shenandoah Valley and along with John C. Fremont, Irvin McDowell and Nathaniel Banks surrounded Thomas Stonewall Jackson and his 17,000 man army. First Jackson attacked John C. Fremont at Cross Keys before turning on Irvin McDowell at Port Republic. Jackson then rushed his troops east to join up with Joseph E. Johnston and the Confederate forces fighting McClellan.
Major General John Pope, the commander of the new Army of Virginia, was instructed to move east to Blue Ridge Mountains towards Charlottesville. It was hoped that this move would help George McClellan by drawing Robert E. Lee away from defending Richmond. Lee's 80,000 troops were now faced with the prospect of fighting two large armies: McClellan (90,000) and Pope (50,000)
Joined by Thomas Stonewall Jackson, James Longstreet, and George Pickett, the Confederate troops attacked George McClellan at Gaines Mill. and on 27th June. After severe fighting the Union Army was forced to retreat. Union Army losses were 893 killed, 3,107 wounded and 2,836 missing. Whereas the Confederate Army had 8,751 killed and wounded.