The First Battle of Bull Run fought on July 21, 1861, is often referred to as the first major battle of the Civil War.

Taking place near Manassas, Virginia, this confrontation involved inexperienced troops on both sides, with the Union aiming to quickly defeat the Confederates and secure a swift end to the conflict. However, the battle ended in a surprising Confederate victory, leading to a chaotic retreat of Union forces. This outcome dispelled any notions of a quick war and underscored the need for better preparation and strategy, setting the stage for a protracted conflict.