"You are green, it is true, but they are green also; you are all green alike," said President Abraham Lincoln to Brig. Gen. Irvin McDowell. He insisted that McDowell set out with his inexperienced and undisciplined army and at long last confront the insurgent Confederate army camped near the small town of Manassas.
At 2:00 P.M. on July 16, The untried Union army of 35,000 Union soldiers set out in 3 columns from their works on the south bank of the Potomac River on the first of the Union's many attempts to capture the Confederate capitol of Richmond. The lighthearted soldiers made slow progress on this first march, stopping to rest or pick blackberries alongside the road. The Confederate army was concentrated around the vital railroad junction at Manassas. They had about 22,000 men, under the command of Brig. Gen. P.G.T. Beauregard, and guarded the fords of Bull Run.
The advance elements of McDowell's troops cautiously entered Centreville about 9:00 A.M. on the 18th. The Federals did not find any Confederates, only abandoned earthworks, trenches, and a signal tower. Brig. Gen. Daniel Tyler, commanding the Northern troops, ordered a halt, asked for further instructions, and gathered local citizens for information. Tyler learned that the Confederates had withdrawn during the night to a stone bridge over Bull Run Creek and toward Blackburn's Ford. Directed by McDowell not to bring on an engagement but to observe the roads toward the creek, Tyler sent Col. Israel B. Richardson's brigade south toward the ford; sometime after noon the Federals found it.
Tyler and Richardson examined the crossing, where the Bull Run bent southward in a loop. From the Union position in a woodland, a cleared field sloped down to the stream's bank, which was heavily covered in underbrush and trees. The 2 officers located a section of a Confederate battery but not any infantry in any strength at Blackburn's or Mitchell's Ford farther upstream. Tyler decided to test the Confederate position and strength.
Tyler's advance brigade, commanded by Richardson, arrived near Blackburn's Ford on Bull Run Creek. Spotting a Confederate battery across the valley, Tyler had 2 of his cannon fire upon the Confederate battery that he had seen and sent 2 regiments, 2 cannon, and a squadron of cavalry down toward the ford to reconnoiter. The Union soldiers had swept down the hillside and closed on the ford when they were suddenly hit with a murderous volley of musketry that erupted from the trees on the other bank. They had encountered Col. James Longstreet's brigade of 3 Virginia regiments. The fierce little firefight that ensued lasted for more than an hour. He was repulsed. This action was a reconnaissance-in-force prior to the main event at Manassas/Bull Run. Because of this action, McDowell decided on the flanking maneuver he employed at the battle of First Manassas.
Longstreet received reinforcements from Gen. Jubal A. Early's brigade and launched 2 regiments across Bull Run in a counterattack that routed the Union troops at the ford.
Because Tyler had been ordered not to bring on a general engagement, he withdrew Richardson's brigade, ending the skirmish. The Union soldiers had suffered 19 killed, 38 wounded, and 26 missing. The Confederates had 15 killed and 53 wounded and felt that they had won a great victory in preventing the Union troops from crossing the creek. Three days later, the Union troops managed to cross in force and brought on the 1st Battle of Bull Run.
Confusingly, the Confederates called this skirmish at Blackburn's Ford the "Battle of Bull Run." The battle they fought 3 days later they named the "1st Battle of Manassas". The skirmish at Blackburn's Ford was also known as the "Prelude to the 1st Bull Run".