When the firing began both sides believed that the war would be a quick one. The North believed it could bring superior forces to bear and subdue the rebellion quickly. The South believed that they just simply needed to show the North that they meant business and with a little force they would get their way. Only a little bit of fighting would be needed. Oh how wrong they were.
Lincoln called for 75,000 volunteers to put down the rebellion, a call which prompted many of the states in the Upper South to secede. Volunteers rushed to Washington DC to defend the capitol and it was isolated for a brief time early in the war. Winfield Scott, the aging army commander laid out the strategy. The navy would blockade the South and the army would be used to deliver the deathblow along the Mississippi. Lincoln adopted some of the blockade but the Mississippi would have to wait since there was a more immediate danger with Confederate forces in Virginia. Irvin McDowell was placed in command of the new army being built in Washington, 35,000 men, or a larger army than any other commander in American history had commander to that point. Lincoln urged action, but McDowell needed time to train the men. Lincoln though would eventually get his way.
In the new capitol of Richmond, Confederate President Jefferson Davis was also raising an army. He had a military background and have served in nearly every level of high government. He was much more qualified to get things moving than Lincoln was at this stage and he too began building an army. P.G.T. Beauregard was sent to take command of Confederate forces in Northern Virginia, about 22,000 men. He was the hero of Fort Sumter and a dashing figure that inspired confidence all throughout the South.
The Union army was confined to Washington and needed to push the Confederates away from Northern Virginia. Most of the Confederate army was concentrated near the rail junction at Manassas with a smaller army in the Shenandoah Valley under Joseph Johnston of about 8,900 men. Confronting that army was about 18,000 men under Robert Patterson, an aging longtime soldier who was well past his prime.
Lincoln’s urgings finally got to McDowell who began to move out. His army was not ready but Lincoln believed that neither was the Confederate army. Unfortunately for him, his plans were known to Confederate spies who passed them on to Beauregard who was prepared when his army marched out of Washington on July 16. One column would make a diversionary attack near Bull Run Creek with another column moving around the flank to cut the railroad. McDowell assumed this would cause the Confederates to retreat. McDowell needed to act quickly as his intelligence suggested that Johnston was moving to link up with Beauregard. It didn’t help either that his men’s 90 day enlistments were also nearly up.
McDowell changed his plans when he neared Manassas. Two divisions would be sent around the flank with another advancing up the Warrenton Turnpike and if successful they could get into the Confederate rear. The plan was good if he had experienced commanders and soldiers but he did not. He also needed Patterson to hold Johnston in The Valley, which he did not.
By July 20 Johnston’s men were already arriving on scene and were positioned near Blackburn’s Ford. Beauregard wanted to attack toward the Centreville Road and hit McDowell there. At this point McDowell’s intelligence was failing him and he called in a balloon observer who gave him the information he needed.