Battle of Manassas or Bull Run

The First Battle of Bull Run (July 21, 1861), called the Battle of First Manassas by Confederate forces, was the first major battle of the American Civil War. It was a Confederate victory. After this Union defeat, Brig. Gen. Irvin McDowell, the commander of the Union Army of Northeastern Virginia, was relieved and replaced by Maj. Gen. George B. McClellan, who set about reorganizing and training what would become the Army of the Potomac. (Photo by: Ivy Close Images/Universal Images Group via Getty Images)