Gen. Tyler ordered his Federal division forward to occupy Centerville shortly after 7:00 a.m. on July 18. Col. Richardson’s brigade led the column. Tyler prudently threw out pickets to prevent an ambush, followed by a light infantry battalion under Captain Robert Brethschneider composed of forty men from each of Richardson’s four regiments. The captain’s command marched about one-half mile in front of the main column, supported by Lt. Benjamin’s section (a pair of twenty-pounder rifled guns) of Lt. John Edwards’ Battery G, 1st U.S. Richardson’s men entered Centreville about 9:00 a.m. to find the town deserted: Cocke’s rebels had hastily retreated the night before.1
Once he reached Centreville, Tyler was to watch the roads running to Bull Run and Warrenton and not bring on an engagement. However, when he learned from local residents that the enemy could not have gone far, Tyler continued marching south in direct violation of McDowell’s orders. His men halted about one mile south of Centreville to fill their canteens. While they rested, Tyler suggested that Richardson accompany him on a reconnaissance toward Mitchell’s Ford some two miles distant. The generals took Captain Brethschneider’s men and three companies of the 1st Massachusetts with them, along with a squad of cavalry. The column moved south along the Manassas-Centreville Road. The Federals moved close enough to see that the ford was defended by what was estimated to be a brigade-strength command (Bonham’s). Tyler shifted his march left (southeast) along an inconsequential farm lane leading to Blackburn’s Ford. To the “astonished” Tyler, no enemy was visible defending the high ground behind the ford.2
In fact, the Confederates were there in strength: James Longstreet’s Brigade was resting amongst the trees on the opposite side of the ford, with a well hidden skirmish line covering his front. Six companies of the 1st Virginia guarded the farm lane that crossed the creek at the ford, with the other four regiments waiting in reserve in the rear. The 17th Virginia was on the left of the 1st Virginia, with the 11th Virginia extending the line south by southwest along the curving creek. All told, these regiments totaled perhaps 1,200 men. A pair of guns from the Washington Artillery unlimbered behind and to the right of the 1st Virginia, but Longstreet did not have much confidence in the small six-pounders. Several other brigades in that sector were available for support, including Bonham’s at Mitchell’s Ford, Jones’ at McLean’s Ford, and Ewell’s at Union Mills Ford farther to the right. The most readily accessible reserve was Jubal Early’s Brigade, in position near the McLean house.3
While pondering his next move, an aide from McDowell’s staff arrived to remind Tyler not to trigger a battle. The Gen. waved off the warning and ordered Benjamin’s guns (long range twenty-pounders) to open fire about noon from near the Butler house. The guns fired down the road at Captain Delaware Kemper’s Alexandria Artillery battery (outdated and short-range six-pounder pieces) situated north of Mitchell’s Ford. Kemper’s guns responded with six rounds, but all fell far short of Benjamin’s guns. Kemper wisely ordered his Virginia battery back across the stream. Benjamin shifted his attention to the two small guns defending Blackburn’s Ford. To Tyler’s dismay, the artillery fire did not stir the Confederates enough to reveal themselves. Determined to press ahead, Tyler ordered Brethschneider’s light battalion to force the issue (No. 1 on the map). A fresh battery under Captain Romeyn Ayres (Battery E, 3rd U.S., or Sherman’s Battery, named after Thomas Sherman) arrived and dropped trail next to Benjamin’s section near the Butler house. A second McDowell aide arrived to counsel caution, but Tyler ignored him as well. When Brethschneider’s men tumbled back from the woods lining the creek, Tyler advanced three companies of the gray-clothed 1st Massachusetts (No. 2 on map). Some of Longstreet’s men fell back, believing the Massachusetts men numbered in the thousands. It took a mounted Longstreet with an unsheathed sword to get the green soldiers back into line. As the Federals approached Blackburn’s Ford, the hidden Confederate infantry opened fire, killing and wounding many of the attackers. The Bay Staters held their ground and returned the fire.4