Through the month of June 1863, the Army of the Potomac made two large operational pivots. The first pivot took place after the Battle of Brandy Station with the army moving off the Rappahannock River, where it faced generally south, into a position facing west. As my friend Clark Hall mentioned in the comments yesterday, the Bull Run Mountains and Catoctin Mountain formed a geographic shield. But that pivot was not complete on this day (June 18) in 1863. The army was still in motion.
What worried Major-General Joseph Hooker at this time 150 years ago were reports of Confederate activity at Point of Rocks, about half way between Leesburg and Harpers Ferry. With fears the Rebels might launch a cavalry raid into Maryland (and not realizing a portion of their infantry was already in Maryland), Hooker ordered forward his own infantry. To Major-General Henry Slocum’s Twelfth Corps at midnight on June 17:
The major-general commanding directs that, on receipt of this order, if after 3.30 a.m. or at that hour, you move your corps to Leesburg. Hold it, and open communication with the fords on the Potomac in that vicinity, and hold them. Captain McKee, with a detachment of cavalry of this army, ought to be at the mouth of the Monocacy to-night; bridge trains and two regiments of infantry to-morrow noon. General Pleasonton encountered Fitz. Lee’s brigade of cavalry at Aldie at 4 o’clock this afternoon. Stuart was reported at Middleburg. The inclosed dispatch would lead to a presumption that they are there to cover White’s crossing the river, or else to join him. This must be prevented. General Pleasonton may be sending in a force toward Leesburg, as he has been directed to do so. Guard against collision with him. Inform his officers there, should you meet them, of all you can learn regarding enemy’s movements.
Hooker ordered the Eleventh Corps to stand ready move in support should the Twelfth encountered resistance. The Fifth Corps would remain in place at Gum Springs. Captain Samuel McKee, mentioned in the orders to Slocum, moved to secure river crossing points from the Maryland side. If all these movements were completed with vigor, any attempt by Confederate cavalry to break into Maryland would end before getting started. Only one problem… the Stuart’s cavalry wasn’t planning to splash across the Potomac that day. As Captain McKee reported mid-afternoon, “Nothing has been seen or heard of the enemy here today.”
Hooker anticipated Twelfth Corps in Dranesville might reach Leesburg by mid-day. As Major-General John Reynolds observed, Slocum had trouble crossing Goose Creek due to bad, rocky fords. There were no bridges over the lower portion of Goose Creek. Afternoon rainstorms further delayed the Twelfth Corps. Slocum did not close on Leesburg until 5 p.m.
From Aldie, Brigadier-General Alfred Pleasonton sent out patrols towards Middleburg. He also posted a brigade at Thoroughfare Gap. A “Bull Run-Catoctin line” was taking shape.
As the Army of the Potomac’s cavalry was stretched thin, Hooker requested two regiments of Major-General Julius Stahel’s division to reconnoiter to Warrenton and Sulpher Springs to the south. Stahel would send Colonel Othniel De Forest with two regiments to fill this request.
Meanwhile, the engineers of the army were also busy. For the last week, the brigade worked to pull in the bridges placed at Fredericksburg earlier in the month, then transport the lot to Washington. Summarizing the state of readiness, Brigadier-General Henry Benham reported:
I am now about to bring the bridges from Alexandria to this depot for rearrangement and repairs. We have nearly 200 pontoons to examine and refit into bridges, and about 1,200 animals of the trains to care for, while the total effective force of my brigade, excepting the company and fractional company at work in this depot, and that company at Harper’s Ferry, is only about 1,000 to 1,100 men, and of these 600 are now up the Potomac, under Major Spaulding and Captain Turnbull; and the balance of the command, … should, as I would respectfully recommend, all be concentrated at this depot, where the services of all will be required for the care and guarding of this large number of animals and the speedy restoration of the bridges to a serviceable condition, which will be immediately reported to headquarters.
This early in the campaign, the engineers were already hard pressed.
As June 18 came to a close, Hooker’s headquarters sent out a circular with instructions to “exclude all excess of personal baggage” and generally clean up the wagon trains. The army needed to move faster, with fewer encumbrances. At the close of the circular, a summary of the army’s dispositions read:
The general headquarters will be at Fairfax Court-House to-night. Telegraphic communication will be established to General Reynolds’ camp, near Guilford Station. [where First Corps would move on the 19th]
The Twelfth Corps is at Leesburg; the Eleventh on Goose Creek, near Trappe Rock, 4 miles from Leesburg; the Fifth Corps, General Meade, at Gum Springs; cavalry in the vicinity of Aldie; the Sixth Corps at Germantown; Second Corps at Sangster’s Station. General Pleasonton engaged Fitzhugh Lee’s brigade, of Stuart’s cavalry, at Aldie yesterday, capturing 9 officers and 74 men.
The Army of the Potomac was not finished with this first pivot, but the line was forming across Loudoun. The 19th would bring both marching and fighting.
(Citations from OR, Series I, Volume 27, Part III, Serial 45, pages 178, 193, 194, 197, and 198.)