The pace of the campaign began to pick up on September 9. Robert E. Lee, hopeful that the Federal garrisons in the lower Shenandoah Valley, realized that he would have to nudge them away from his supply line. Accordingly, Lee dictated and distributed Special Order No. 191 to his subordinate commanders. The bold plan outlined the division of the Army of Northern Virginia, with nearly two-thirds of it under “Stonewall” Jackson eliminating the obstinate garrisons.
Further east of Frederick, the Federal and Confederate cavalry screens clashed at Hyattstown, Monocacy Church, and Barnesville. At Monocacy Church, a member of the 8th Illinois Cavalry recalled the fight.
The regiment was now divided into several detachments. One of these under command of Captain Farnsworth, encountered the Ninth Virginia Cavalry, and immediately charged them. The enemy formed in line and withstood the attack for a moment, but gave way before the determined charge of our men, in doing which some of their horses were shot down, and others falling over these, both men and horses were thrown into heaps. Some escaped through fields and woods, while others were chased and overtaken by our superior horsemen.
The running fight that began at Monocacy Church and ended at Barnesville yielded not a single Federal casualty while Confederate losses totaled 36.
As the two opposing cavalries kept up a near-constant fight, the rest of the Army of the Potomac continued its march toward Frederick. Captain William Bolton of the 51st Pennsylvania Infantry recorded the difficulties–and pleasures–of his march through Maryland.
Sept 9–Regiment left their bivouac at 6 o’clock A.M. passed through Mechanicsville and arrived at Brookeville Md. about noon, making fifteen miles in less than six hours. Our march through this section of the country was indeed very pleasant. We were received by the people in great kindness, distributing fruit cakes and pies to the troops very freely. The regiment went into bivouac near a fine stream of water which gave us a royal chance to bathe and to wash our clothing. Here we also received an abundance of rations the first for many days.