The Second Battle of Bull Run (Manassas) proved to be the deciding battle in the Civil War campaign waged between Union and Confederate armies in northern Virginia in 1862. As a large Union force commanded by John Pope waited for George McClellan’s Army of the Potomac in anticipation of a combined offensive, Confederate General Robert E. Lee decided to strike first. Lee sent half of his Army of Northern Virginia to hit the Federal supply base at Manassas.