John G. Nicolay, The Outbreak of Rebellion

[179] three were deployed in line of battle to make a new charge, that Tyler heeded his instructions, and withdrew his reluctant officers and men from the fight, partly demoralized and generally exasperated, and returned to Centreville. In point of fact, the loss, the damage, the demoralization, had been equal on both sides. The rebel reports show that three regiments of Longstreet's brigade, which bore the first assault, were so much shaken that Early's reserve brigade of three fresh regiments was called up and relieved them, that one of these regiments was thrown into confusion, and that the rebel loss was sixty-three killed and wounded. Undecisive as it was, the battle of Blackburn's Ford had an important effect. It confirmed Beauregard in his previous impression that the principal Union attack would be made at that point on the centre of his long line. On the other hand, McDowell, receiving from his officers reports of rifle-pits and breastworks, became convinced that a direct assault was unwise. The affair of Blackburn's Ford thus proved something more than a preliminary defeat; it augmented the causes of a great disaster. Upon hearing the cannonade, McDowell had immediately ordered all the divisions forward to Centreville. He had already in his own mind given up the plan of turning the enemy's right, because of the unfavorable nature of the ground and roads. The necessity of finding an unfortified crossing seemed now also demonstrated. Meeting his division commanders at Centreville, that same night of Thursday, July 18th, McDowell informed them confidentially that he had abandoned his original plan, and had resolved to make the attack by marching northward and turning Beauregard's left flank instead of his right.

As an incident of this resolve, however, it was even more essential than before to continue to threaten the enemy's