The First Battle of Bull Run (the name used by Union forces), also known as the First Battle of Manassas (the name used by Confederate forces), is the first major battle of the American Civil War and is a Confederate victory.

The battle is fought on July 21, 1861 in Prince William County, Virginia, just north of the city of Manassas and about twenty-five miles west-southwest of Washington, D.C.

The Union's forces are slow in positioning themselves, allowing Confederate reinforcements time to arrive by rail.

Each side has about 1eighteen thousand poorly trained and poorly led troops in their first battle

It is a Confederate victory, followed by a disorganized retreat of the Union forces.

Just months after the start of the war at Fort Sumter, the Northern public clamors for a march against the Confederate capital of Richmond, Virginia, which is expected to bring an early end to the rebellion.

Yielding to political pressure, Brig. Gen. Irvin McDowell leads his unseasoned Union Army across Bull Run against the equally inexperienced Confederate Army of Brig. Gen. P. G. T. Beauregard camped near Manassas Junction.

McDowell's ambitious plan for a surprise flank attack on the Confederate left is poorly executed by his officers and men; nevertheless, the Confederates, who have been planning to attack the Union left flank, find themselves at an initial disadvantage.

Confederate reinforcements under Brig. Gen. Joseph E. Johnston arrive from the Shenandoah Valley by railroad, and the course of the battle quickly changed.

A brigade of Virginians under the relatively unknown brigadier general from the Virginia Military Institute, Thomas J. Jackson, stands its ground, which results in Jackson receiving his famous nickname, "Stonewall".

The Confederates launch a strong counterattack, and as the Union troops begin withdrawing under fire, many panic and the retreat turns into a rout.

McDowell's men frantically run without order in the direction of Washington, D.C.

Both armies are sobered by the fierce fighting and many casualties, and realize that the war is going to be much longer and bloodier than either had anticipated.

The First Battle of Bull Run highlights many of the problems and deficiencies that are typical of the first year of the war.

Units are committed piecemeal, attacks are frontal, infantry fails to protect exposed artillery, tactical intelligence is nil, and neither commander is able to employ his whole force effectively.

McDowell, with thirty-five thousand men, is only able to commit about eighteen thousand and the combined Confederate forces, with about thirty-two thousand men, commit only eighteen thousand.