At the First Battle of Bull Run, near Manassas, Virginia, Union forces under General Irvin McDowell were defeated by the Confederates. McDowell delayed the attack for two days, allowing Confederate General Beauregard to call on reinforcements from the Shenandoah Valley. Their arrival late in the day gave the Confederates a numerical advantage. It was in this battle that Confederate General Thomas J. Jackson was nicknamed "Stonewall" for his firm stand at a crucial moment.