Jackson's wing of the army, after passing around Pope's right flank via Thoroughfare Gap, had struck the Orange & Alexandria Railroad at Bristoe Station on the evening of August 26 and before daybreak August 27 marches to capture and destroy the massive Union supply depot at Manassas Junction.

This surprise movement forces Pope into an abrupt retreat from his defensive line along the Rappahannock.

On August 27, Jackson routs the New Jersey Brigade of the VI Corps near Bull Run Bridge, mortally wounding its commander George W. Taylor.

Major General Richard S. Ewell's Confederate division fights a brisk rearguard action against Major General Joseph Hooker's division at Kettle Run, resulting in about six hundred casualties.

Ewell holds back Union forces until dark.

Jackson marches his divisions north to the First Bull Run (Manassas) battlefield, where he takes position behind an unfinished railroad grade during the night of August 27 – August 28.

Robert E. Lee decides in June 1863 to capitalize on his victory at Chancellorsville by repeating his strategy of 1862 and once again invading the North.

He does this to resupply his army, give the farmers of Virginia a respite from war, and threaten the morale of Northern civilians, possibly by seizing an important northern city, such as Harrisburg, Pennsylvania, or Baltimore, Maryland.

The Confederate government agrees to this strategy only reluctantly because Jefferson Davis is concerned about the fate of Vicksburg, Mississippi, the river fortress being threatened by Ulysses S. Grant's Vicksburg campaign.

Following the death of Jackson, Lee has organized the Army of Northern Virginia into three corps, led by Lieutenant Generals James Longstreet, Richard S. Ewell, and A.P. Hill.

Lee begins moving his army northwest from Fredericksburg into the Shenandoah Valley, where the Blue Ridge Mountains screen their northward movements.

Joseph Hooker, still in command of the Army of the Potomac, sends cavalry forces to find Lee.

The clash at Brandy Station on June 9 is the largest predominantly cavalry battle of the war but ends inconclusively.

Confederate General Richard S. Ewell defeats a Union garrison at the Shenandoah Valley town of Winchester, Virginia, from June 13 to 15.

After the Battle of Brandy Station on June 9, Lee had ordered Ewell's nineteen thousand-man Second Corps, Army of Northern Virginia, to clear the lower Shenandoah Valley of Union opposition so that Lee's army can proceed on its invasion of Pennsylvania, shielded by the Blue Ridge Mountains from Union interference.

Union General-in-chief Henry Wager Halleck has expressed great concerns about the Middle Department's defensive strategy for its primary objective of protecting the Baltimore and Ohio Railroad corridor.

Brigadier General Benjamin Franklin Kelley, commander of the "railroad division" (Department of Harper's Ferry), had been advised that his plan, along with Major General Milroy's and Major General Robert C. Schenck's (Commander of the Middle Department), was unsound.

The victory at Second Winchester clears the Valley of Federal troops and opens the door for Lee's second invasion of the North.

The capturing of ample supplies justifies Lee's conceptual plan to provision his army on the march.

The Federal defeat stuns the North, and Secretary of War Edwin M. Stanton will call for additional militia to be federalized.

Shortly afterward, President Lincoln requests one hundred thousand volunteers to repel the threatened invasion.

Several fleeing members of the scattered 87th Pennsylvania hastily tramp back to their homes near Gettysburg and in adjoining York County, Pennsylvania, spreading news to local officials that the Confederates are now in the Valley in strength, with apparent designs on invading Pennsylvania.

Governor Andrew Curtin of Pennsylvania, in response to these reports and other military intelligence, calls for fifty thousand volunteers to protect the Keystone State.

Lee, having defeated Hooker's Union forces at Chancellorsville, decides to invade the North in hopes of further discouraging the enemy and possibly inducing European countries to recognize the Confederacy.

Lee's Army of Northern Virginia, seventy-five thousand strong, begins a second invasion of the North, by way of the Shenandoah Valley into southern Pennsylvania.

Hooker follows him closely with the Army of the Potomac.

The Battle of Aldie in the Gettysburg Campaign ends inconclusively on June 17.

Tensions have grown between Hooker and his cavalry commander Brigadier General Alfred Pleasonton because of the latter's inability to penetrate Major General J.E.B. Stuart's cavalry screen and gain access to the Shenandoah Valley to locate the Army of Northern Virginia, which has been on the move since the Battle of Chancellorsville in early May.

Pleasonton had decided on June 17 to push through Stuart's screen.

To accomplish his goal, he had ordered Brigadier General David McMurtrie Gregg's division from Manassas Junction westward down the Little River Turnpike to Aldie.

Aldie is tactically important in that near the village the Little River Turnpike intersects both the Ashby's Gap Turnpike and Snicker's Gap Turnpike, which respectively lead through Ashby's Gap and Snickers Gap of the Blue Ridge Mountain into the valley.

Munford does not consider Aldie as a defeat as his withdrawal coincides with an order from Stuart to retire, as more Federal cavalry had been sighted at Middleburg.

Union casualties are three hundred and five dead and wounded, with the Confederates losing between one hundred and ten and one hundred and nineteen.

Aldie is the first in what will be a series of small battles along the Ashby's Gap Turnpike in which Stuart's forces successfully delay Pleasonton's thrust across the Loudoun Valley, depriving him of the opportunity to locate Lee's army.

General Ewell had crossed the Potomac on June 17, and by June 23 is nearing Chambersburg, Pennsylvania.

...before General Lee, at Chambersburg, Pennsylvania, knows about it.

Ewell captures Carlisle and ...