History: American Civil War (1861-1865)

Eastern theater 1861–1863
Because of the fierce resistance of a few initial Confederate forces at Manassas, Virginia, in July 1861, a march by Union troops under the command of Maj. Gen. Irvin McDowell on the Confederate forces there was halted in the First Battle of Bull Run, or First Manassas, McDowell's troops were forced back to Washington, D.C., by the Confederates under the command of Generals Joseph E. Johnston and P. G. T. Beauregard. It was in this battle that Confederate General Thomas Jackson received the nickname of "Stonewall" because he stood like a stone wall against Union troops.
Alarmed at the loss, and in an attempt to prevent more slave states from leaving the Union, the U.S. Congress passed the Crittenden-Johnson Resolution on July 25 of that year, which stated that the war was being fought to preserve the Union and not to end slavery.