The commotion created by the approach of the invader was not all one-sided. General Dix, who commanded at Fortress Monroe, received orders to advance on Richmond, which was weakly defended at this time. As through their manifold offences in the way of starving our prisoners, etc., the rebel President and his cabinet were afraid of reprisals, there was great dismay at the weakness of the garrison there, and bitter denunciations of Lee for leaving so small a force behind. The Union troops for this counter-invasion were landed at Yorktown and sent on to the White House. General Getty, in command of one column of about seven thousand men, moved on the 13th as far as Hanover Junction to destroy the bridge over the North and South Anna, and as much of the railroad as possible, in order to make a break in Lee's communications. At the same time General Keyes, with another column of about five thousand men, moved from the White House to secure Bottom's Bridge on the Chickahominy, and thus leave a clear road for Getty's column to advance on the city. The Davis Government, however, called out the militia and concentrated enough men for defence by weakening the garrisons in South Carolina and elsewhere; but there is no doubt the fright at one time was so serious that it was in contemplation to recall Lee's forces; especially on the 15th of June, when it was learned that General Keyes' column was at New Kent Court House within fifteen miles of the city.
On the 16th Stuart's cavalry left the Rappahannock—with the exception of the 15th Virginia, which remained with Hill—and bivouacked at Salem with Fitz Lee's brigade at Piedmont. Their orders were to keep along the eastern base of the Blue Ridge, and guard the front of Longstreet's corps in the Gaps.
Our own cavalry were concentrated at Warrenton and Catlett's.
On the 17th Fitz Lee's brigade was sent forward from Piedmont to Aldie, via Middleburg, to anticipate our troops in holding the Gap there; it being considered important to occupy the Bull Run range of mountains as a screen for Lee's further operations. Fitz Lee's brigade was supported by that of Robertson which was moved to Rectortown, where it was also available as a reserve to W. H. F. Lee's brigade which had gone forward to occupy Thoroughfare Gap. No opposition was anticipated in the latter place, Pleasonton having moved to Centreville, with his main body. Stuart made his headquarters at Middleburg on the 17th.
Fitz Lee halted near Dover to close up his command, and sent his pickets on to Aldie Gap. Pleasonton, who was scouting in the vicinity, had no orders to go through the pass, but felt prompted to do so by one of those presentiments which rarely deceive. He pushed on, therefore, with Gregg's division until about 2.30 P.M., when he came upon the rebel pickets, who fell back on the main body. The latter had made a march of forty miles to reach the Gap, and Fitz Lee chose a strong position on a hill directly west of Aldie, in which to fight a defensive battle. His line covered the road to Snicker's Gap, but could be turned by the road to Middleburg and Ashby's Gap.
A sanguinary contest ensued, which, including the pursuit, lasted until 9 P.M. The rebel front was strengthened by a ditch and a line of hay-stacks. After fighting for three hours the battle was finally decided by a gallant charge of the 1st Maine Cavalry, who, after our line had been broken and driven back, were led by Kilpatrick in person, against a regiment of mounted infantry on the Ashby's Gap road, capturing four guns. The Harris Light Cavalry had been in disfavor for having failed in an attack at Brandy Station, but on the present occasion they redeemed themselves, made several brilliant charges, and greatly contributed to the success of the day.
The rebels claim to have taken 134 prisoners, and some flags in this affair, and state that they only fell back to Middleburg in obedience to Stuart's orders. Ascertaining that Colonel Duffie was advancing on that place with his division, Stuart thought, by concentrating his entire force there, he could overwhelm him. This may account for the retreat, but it is very certain that the loss of the pass at Aldie was a serious blow to the rebel cause. This, supplemented by Colonel Duffie's operations, which will be described hereafter, gave Hooker possession of Loudon County, and threw the invading column far to the west. If the enemy had succeeded in posting forces in the gaps of the Bull Run range of mountains, and in occupying the wooded country between Thoroughfare Gap and Leesburg, they would not only have hidden all their own movements from view, but would have had command of the Potomac from Harper's Ferry to within thirty miles of Washington, so that they could have operated on either side of the river.
While Gregg's division were thus engaged, Colonel Duffie started under orders with his regiment from Centreville for Middleburg, by way of Thoroughfare Gap. The enemy (W. H. F. Lee's brigade) were already there, but he forced them out, and kept on to Middleburg, which was reached about 9.30 A.M. He found Stuart's rear guard or escort there, and drove them out. Stuart fell back to Rector's Cross Roads, and sent word to all his forces to concentrate against Duffie. Duffie barricaded the streets of the town and prepared to hold it until reinforcements could reach him from Aldie, not being aware that there was any impediment in that direction. At 7 P.M. the different rebel brigades advanced on him from the direction of Aldie, Union, and Upperville. By sheltering his men behind stone walls and barricades, he repelled several assaults, but at last was surrounded by overwhelming forces, and compelled to retreat by the road upon which he had advanced in the morning. He fell back until he crossed Little River, picketed the stream and halted there to get some rest. This gave time to the enemy to surround him, and by half past one the next morning all the roads in the neighborhood were full of cavalry; an entire brigade being formed on that which led to Aldie. He tried to force his way through the latter, but was received with heavy volleys on both flanks, and with loud calls to surrender. He directed Captain Bliss and Captain Bixby, who were in advance, to charge through everything in front of them, and the way was cleared for the main body, which at last gained the junction of the Aldie road with that which leads to White Plains. He then retreated on the latter, with his men all intermixed with those of the enemy and fighting every step of the way. He finally disengaged his force from this mélée and made his way through Hopewell Gap back to Centreville, losing two-thirds of his command.
In this affair at Middleburg, Stuart states that he was unable with his entire force to drive the 1st Rhode Island regiment from a position it had chosen, and speaks with admiration of the gallantry it displayed.
On the 18th, Stuart took post outside of that town with Robertson and W. H. F. Lee's brigade. Fitz Lee's brigade was on his left at Union, and Jones' brigade was ordered up as a reserve.