The First Battle of Bull Run was fought on July 21st 1861. Bull Run was the first major battle of the American Civil War and the area also saw the Second Battle of Bull Run in 1862.Union forces referred to the battle as Bull Run whereas the Confederacy called the battle the Battle of Manassas. The American Civil War broke out in April 1861 with the attack on Fort Sumter.ull Run was the first major battle of the American Civil War and the area also saw the Second Battle of Bull Run in 1862.