Why the cavalry screen?

[infomanpa]

A question occurred to me while I was on the trail of the Gettysburg campaign:

Lee considered it vital that his cavalry screen his advance through the Shenandoah Valley on his way north to Pennsylvania. After his army attacked the Union garrison at Winchester, VA on June 13, wouldn't he have "blown his cover?" I would assume that General Milroy, commander of the garrison would have telegraphed Washington about the presence of Lee's men. By June 15, Rebel cavalry was already into Pennsylvania. By the time (after June 16) that Hooker sent his Union cavalry into the Loudoun Valley to find Lee's army, he should already have known from telegrams that Lee was in the Shenandoah Valley and already threatening the north. Am I mistaken about the speed of telegraph communications?

 

[ronzzo]

I think the screen was necessary to give the Confederates a head start to Pennsylvania while keeping the Union army guessing. While he may have shown his hand at Winchester, he was well advanced to his objective.

 

[datameister]

A question occurred to me while I was on the trail of the Gettysburg campaign:

Lee considered it vital that his cavalry screen his advance through the Shenandoah Valley on his way north to Pennsylvania. After his army attacked the Union garrison at Winchester, VA on June 13, wouldn't he have "blown his cover?" I would assume that General Milroy, commander of the garrison would have telegraphed Washington about the presence of Lee's men. By June 15, Rebel cavalry was already into Pennsylvania. By the time (after June 16) that Hooker sent his Union cavalry into the Loudoun Valley to find Lee's army, he should already have known from telegrams that Lee was in the Shenandoah Valley and already threatening the north. Am I mistaken about the speed of telegraph communications?

Speed could vary! Milroy (a horrible person even by a 19th Century perspective) was caught unaware of the danger from Ewell's Corps. Halleck told Milroy's superior, Schenk, that Winchester, "should" be evacuated. This is classic Halleck with his weak discretionary orders.

Schenk received some bluster-filled response from Milroy and told him to be ready to evacuate but await further orders.

After Lincoln saw these exchanges, he had enough of the nonsense and fired off, "Get General Milroy from Winchester to Harper's Ferry if possible. He will be gobbled up, if he remains, if he is not already past salvation."

At this time, Hooker et al. were unsure of what Lee's intentions were. A cavalry raid into PA was nothing to lose sleep over.

Also, General Pleasonton was inept at gathering intel, well, inept at everything. He even claimed about this time that Lee's objective was Pittsburg!

Keep in mind that on the 15th of June, A.P. Hill was still at Fredricksburg and Longstreet was departing from Culpepper.

 

[infomanpa]

Speed could vary! Milroy (a horrible person even by a 19th Century perspective) was caught unaware of the danger from Ewell's Corps. Halleck told Milroy's superior, Schenk, that Winchester, "should" be evacuated. This is classic Halleck with his weak discretionary orders.

Schenk received some bluster-filled response from Milroy and told him to be ready to evacuate but await further orders.

After Lincoln saw these exchanges, he had enough of the nonsense and fired off, "Get General Milroy from Winchester to Harper's Ferry if possible. He will be gobbled up, if he remains, if he is not already past salvation."

At this time, Hooker et al. were unsure of what Lee's intentions were. A cavalry raid into PA was nothing to lose sleep over.

Also, General Pleasonton was inept at gathering intel, well, inept at everything. He even claimed about this time that Lee's objective was Pittsburg!

Keep in mind that on the 15th of June, A.P. Hill was still at Fredricksburg and Longstreet was departing from Culpepper.

Thanks for filling in some details. I just didn't understand why Hooker would have bothered to send cavalry to look for Lee, if Halleck had telegraphed him that some of Lee's army had already advanced north though the Shenandoah Valley. I guess that I don't understand what more Hooker could have learned from his cavalry that would have been strategically important.

 

[Eric Wittenberg]

The very short answer is that scouting and reconnaissance were among the primary duties of cavalry. Finding the precise location and exact disposition of Lee's forces was critical intelligence.

And here's something was terribly strategically important: knowing whether all forces available to Lee were with the Army of Northern Virginia, or whether a significant force of troops was left to guard Richmond. Knowing whether Lee could reasonably expect reinforcements was crucial intelligence, and only cavalry could have provided that.