Second Battle of Bull Run - Background and Opposing Forces

Background and Opposing Forces

After the collapse of Maj. Gen. George B. McClellan's Peninsula Campaign in the Seven Days Battles of June 1862, President Abraham Lincoln appointed John Pope to command the newly formed Army of Virginia. Pope had achieved some success in the Western Theater, and Lincoln sought a more aggressive general than McClellan.

The Union Army of Virginia was divided into three corps of 51,000 men, under Maj. Gen. Franz Sigel (I Corps); Maj. Gen. Nathaniel P. Banks (II Corps); and Maj. Gen. Irvin McDowell, who had led the losing Union army at First Bull Run (III Corps). Parts of three corps (III, V, and VI) of McClellan's Army of the Potomac and Maj. Gen. Ambrose Burnside's IX Corps (commanded by Maj. Gen. Jesse L. Reno), eventually joined Pope for combat operations, raising his strength to 77,000.

On the Confederate side, Gen. Robert E. Lee's Army of Northern Virginia was organized into two "wings" or "commands" totaling about 55,000 men. The "right wing" was commanded by Maj. Gen. James Longstreet, the left by Maj. Gen. Stonewall Jackson. The Cavalry Division under Maj. Gen. J.E.B. Stuart was attached to Jackson's wing.

Pope's mission was to fulfill two basic objectives: protect Washington and the Shenandoah Valley; and draw Confederate forces away from McClellan by moving in the direction of Gordonsville. Based on his experience fighting McClellan in the Seven Days, Robert E. Lee perceived that McClellan was no further threat to him on the Virginia Peninsula, so he felt no compulsion to keep all of his forces in direct defense of Richmond. This allowed him to relocate Jackson to Gordonsville to block Pope and protect the Virginia Central Railroad.

Lee had larger plans in mind. Since the Union Army was split between McClellan and Pope and they were widely separated, Lee saw an opportunity to destroy Pope before returning his attention to McClellan. He committed Maj. Gen. A.P. Hill to join Jackson with 12,000 men. On August 3, General-in-Chief Henry W. Halleck directed McClellan to begin his final withdrawal from the Peninsula and to return to Northern Virginia to support Pope. McClellan protested and did not begin his redeployment until August 14.

On August 9, Nathaniel Banks's corps attacked Jackson at Cedar Mountain, gaining an early advantage, but a Confederate counterattack led by A.P. Hill drove Banks back across Cedar Creek. Jackson's advance was stopped, however, by the Union division of Brig. Gen. James B. Ricketts. By now Jackson had learned that Pope's corps were all together, foiling his plan of defeating each in separate actions. He remained in position until August 12, then withdrew to Gordonsville. On August 13, Lee sent Longstreet to reinforce Jackson.

From August 22 to August 25, the two armies fought a series of minor actions along the Rappahannock River. Heavy rains had swollen the river and Lee was unable to force a crossing. By this time, reinforcements from the Army of the Potomac were arriving from the Peninsula. Lee's new plan in the face of all these additional forces outnumbering him was to send Jackson and Stuart with half of the army on a flanking march to cut Pope's line of communication, the Orange & Alexandria Railroad. Pope would be forced to retreat and could be defeated while moving and vulnerable. Jackson departed on August 25 and reached Salem (present-day Marshall) that night.

On the evening of August 26, after passing around Pope's right flank via Thoroughfare Gap, Jackson's wing of the army struck the Orange & Alexandria Railroad at Bristoe Station and before daybreak August 27 marched to capture and destroy the massive Union supply depot at Manassas Junction. This surprise movement forced Pope into an abrupt retreat from his defensive line along the Rappahannock. During the night of August 27–28, Jackson marched his divisions north to the First Bull Run (Manassas) battlefield, where he took position behind an unfinished railroad grade below Stony Ridge. The defensive position was a good one. The heavy woods allowed the Confederates to conceal themselves, while maintaining good observation points of the Warrenton Turnpike, the likely avenue of Union movement, only a few hundred yards to the south. There were good approach roads for Longstreet to join Jackson, or for Jackson to retreat to the Bull Run Mountains if he could not be reinforced in time. Finally, the unfinished railroad grade offered cuts and fills that could be used as ready-made entrenchments.

In the Battle of Thoroughfare Gap on August 28, Longstreet's wing broke through light Union resistance and marched through the gap to join Jackson. This seemingly inconsequential action virtually ensured Pope's defeat during the coming battles because it allowed the two wings of Lee's army to unite on the Manassas battlefield.