Department of the Susquehanna
This is the history of the Department of the Susquehanna, as written by, Willard Brown in his book: The Signal Corps in the War of the Rebellion.
Read more on civil war signals and other departments from the above mentioned book:
     History gives us no record of a more ready or a larger response to the calls of duty, of honor, and of patriotism, than was made by our best young men to the nation's call, in its hour of peril.  Of the personnel of the Signal Corps in this Department, Samuel H Eby says:

     Our detachment, according to the roster of 1864, of which I have a copy, consisted of about sixty-seven men, thirty-eight of whom enlisted in February, 1864, ten in March, thirteen in May, and six at various other dates of the same year.

     The majority of the men in the Corps were school teachers, graduates of some college, or students in some institution of learning.  A number of them came from Pennsylvania College, located at Gettysburg, Pa.

     The Corps was organized in February, 1864.  It encamped about three and one-half miles west of Chambersburg, at which place the recruits were instructed in infantry, cavalry andflag drill.  The Corps remained at this point until the 27th day of June, 1864, when it started for Harper's Ferry, a point in the Department of West Virginia.  After arriving at the Ferry the Corps was devided, the Signal stations established for miles along the Potomac river.  The members of the Corps that were not on signal stations were doing scout duty in the Shenandoah Valley, around Charlestown, Shepherdstown, and Winchester, and through Frederick and Washington counties in the state of Maryland.

     On the 10th of August, 1864, our Corps left the Department of West Virginia and returned to the Department of the Susquehanna, with headquarters at Grencastle, Pa, a town located within four and one-half mils of the Maryland land line.  Signal stations were now established at Williamsport and Fairview, Maryland on the Potomac river, commanding a view of all the ferries for many miles.  Stations were also established in Pennsylvania at Casey's Knob, Greencastle and Mt Parnell.  With this line of stations, news could be transmitted very rapidly from any point along the Potomac to Gen Couch's headquarters.  This same line of stations was kept in operation until the close of the war.  Lieut A M Thayer was Chief Signal Officer of this department until late in the winter of 1864, when he was relieved by Capt Norton.  He only had charge of it about two months.

     I wish to say of Lieut Thayer that he was an excellent officer, mild, though firm; reasonable, yet decided; sharing at all times the hardships with his men, and always treating them courteously.  Capt Norton was succeeded by Capt William S Stryker, who remained in charge of the Corps until September, 1865, when its members were discharged.

     In May, 1864, Lieut Amos M Thayer was ordered to report to Gen Couch at Chambersburg, Pa, as Chief Signal Officer, Department of the Susquehanna, to relieve Capt H Clay Snyder.  The detachment consisted of about forty men recently enlisted in the Corps from the students of Pennsylvania College, located at Gettysburg, Pa.

     They were raw recruits, without horses and without any equipments except their uniforms; but they were first-class material for the Signal Corps.  Lieut Thayer drew horses for the command and other equipments, and drilled the men persistently for about eight hours a day for three weeks.  At the end of that time they were experts in the use of flag and torch, and were moderately well posted in cavalry tactics.  In the meantime Lieut F K McCloskey, G W Kennedy, and M D Reymer had reported.  They were newly commissioned officers in the regular Corps, and had seen no service.  About July 1, 1864, the detachment was ordered to Harper's Ferry, to act as a corps of observation along the upper Potomac.  They arrived just in time (July 3, 1864) to be surrounded on the following day, with all the other Union forces at the Ferry, by the army of Gen Gearly.  Meanwhile the number of enlisted men had been increased to fifty-eight.

     Lieut Thayer had taken particular care while in Camp of Instruction to give the whole party careful instructions in all the different codes, and he felt great confidence in the ability of the Corps to perform efficient service.  The only consideration which tended to weaken this confidence was the small number of officers.  He fully realized that in case of their operations extending over a large field, the party, from no fault of its own, would prove inefficient.

     The first intimation of the approach of the enemy was on Sunday morning July 3rd.  Firing began in the direction of Martinsburg at 4 A.M., and continued without intermission until 9 A.M.  The Signal Officer immediately telegraphed to Gen Sigel's adjutant- general, informing him of the presence of the Signal Corps, and offering to open communication between Maryland Heights and Martinsburg, in case the telegraph lines were cut, as there was every probability they would be.  Lieut Thayer received a telegram in reply thanking him for the offer, but stating that it would be unnecessary, as Martinsburg was being evacuated, and our army was on the retreat to Shepherdstown.

     Our stations at this time connected Gen Weber's headquarters with Maryland Heights and with Fort Duncan, the headquarters of Major Merriam, commanding on the Maryland side.  All communication between these points was maintained through the Signal Corps.  Lieut Thayer took charge of the station at Fort Duncan, as it was the most difficult one, and commanded a fine view of each of the other stations.  Lieut Kennedy on Maryland Heights was instructed to report all movements of troops in that direction, and also the progress of our army in its retreat toward Shepherdstown.

     On the morning of the 4th, at 4 o'clock, having been notified by Lieut Kennedy of the arrival of our army at Shepherdstown, Lieut Thayer again suggested the plan of connecting Gen Sigel's and Gen Weber's headquarters by signals.  The offer as before was declined, our army being again on the retreat to Harper's Ferry.  At 8 A.M., Lieut Thayer signalled to Gen Weber the approach of a large force from Charlestown toward Harper's Ferry.  The information was the first given, and preceded the attack by at least an hour.  Our pickets on the Virginia side were immediately notified, but, notwithstanding the time given for preparation, retreated into the Ferry, leaving Bolivar Heights in possession of the enemy.

     This retreat left the station at Gen Weber's headquarters only a few yards behind the skirmish line; but notwithstanding this, Acting Sergt Thomas J Franklin workrd contiually during the day with great accuracy and coolness, nor did he withdraw until ordered by Gen Weber in person to cross to the Maryland side.

     On Tuesday, the 5th, our forces were all massed on the Maryland side, extending from Fort Duncan to Marylan Heights.  Gen Sigel's headquarters were near the centre of the line, and, in compliance with his request, a station was located there communicating with either flank.  The great difficulty ascending the Heights on either side rendered these stations of vast importance.  At about noon, Lieut Thayer began to suspect from the few reports received from Lieut Kennedy that he was not keeping as close a watch upon the movements of the enemy as might be expected from his commanding position.  For this reason he took station himself upon Maryland Heights, although his proper post should have been at headquarters.

     Immediately upon arriving at the Heights he discovered that the enemy were moving troops and trains up the river on the Virginia side, crossing them into Maryland and moving down toward the Ferry.  He reported this movement to Gen Sigel, and ventured to predict that on the morning of the 6th we should be attacked from the Maryland side.  This prediction was fulfilled, and called forth a personal acknowledgment from the general of the merits of the services of the Signal Corps.

     July 6th, the enemy developed themselves in front of our front on the Maryland side.  Our stations continued to work at the same points day and night, scarcely a moment's intermission occurring during thirty-six hours.  Private William H Crawford was severely wounded in the fight during the afternoon of the 6th, while advancing with our skirmish line.

     During the 7th, the station on the Heights continued to report to headquarters the withdrawal of the trains and troops of the enemy in the direction of Sharpsburg.  These movements became so frequent as to satisfy Lieut Thayer that the attack had been merely to cover the collection of supplies, and that they intended to retreat during the night either up the Shenandoah Valley from Sheperdstown, or accross the South Mountain and Catoctin Mountain toward Frederick City, to cross below Point of Rocks.

     July 8th, the reports of the pervious day were amply confirmed.  No signs of the enemy could be seen in our front.  During the entire day the signal party was employed in endeavoring to discover the enemy's line of retreat.  At 11 A.M. Lieut Thayer informed Gen Sigel that the enemy must be moving on Boonsboro or Frederick, as none could be seen moving up the Shenendoah Valley.  Acting upon the information conveyed in this report, Col Mulligan's brigade and a small body of cavalry were moved toward Point of Rocks, via Jefferson.  Still later in the day, the enemy, having emerged from the mountains which obstructed the view toward the north, were seen from the Heights crossing the Catocin range on the Frederick City pike.  This confirmed previous reports and satisfied the commanding general of the direction and intention of the enemy.  At noon Lieut Thayer sent Lieut Kennedy to report to Gen Stabel, commanding the cacalry in Pleasant Valley, west of South Moumtain, and directed him to go down the valley with the general.  He also instructed him to go to the summit of South Mountain, where a fine view could be obtained of Middletown Valley.  By mistake Lieut Kennedy remained all night in Pleasant Valley and was of no service, save in transmitting a few messages from the cavalry command to headquarters.

     Gen Howe this day assumed command, with headquarters at Sandy Hook, and at 8P.M. the whole detachment was moved to the east of Maryland Heights and the Catoctin Mountain, leaving Lieut Kennedy on the Heights.  During the night, however, our forces under Col Mullian fell back and reported the enemy crossing at Point of Rocks.  Gen Howe sent for the signal officer early on the morning of the 9th, and requested him to remain on the Heights to discover if the enemy were crossing at the point indicated.  He also directed the signal detachment to remain at Sandy Hook ready to move; but he did not consider it safe to attempt to reach the Catotin range.  Lieut Thayer, all this time, reported continually that no force was crossing at Point of Rocks, or had crossed.  He insisted that the main body of the enemy were at or near Frederick.  This report was fully confirmed at 8 o'clock that evening, when scouts came in from Middletown and reported the engagement between Generals Wallace and Early at Monocacy Junction.

     The services of the Signal Corps just recounted show the utility of a signal party in determiningg the movements of an enemy ia a country well adapted to signalling.  For twelve hours the reports furnished by Lieut Thayer were directly opposed to all others.  All evidence but that of the Signal Corps represented the enemy at Point of Rocks, and yet they were found to be exactly where the observations and reports of the Signal Corps located them.

     At noon of the 10th, after the enemy were found to be in the vicinity of Frederick, Gen Howe gave Lieut Thayer permission to establish a station on the Catoctin Mountain, as he himself had desired to do on the previous day.  At daylight he sent the following dispatch:--
     The enemy's forces have left Frederick and are now all across the Monocacy river, save the rear guard of two hundred cavalry.  They are moving on the Georgetown pike.  Gen Wallacw is retreating on the same road.  They are either marching on Washington or Baltimore, or are reteating toward Edward's Ferry.                                                                                                 Thayer,
     Catoctin Mountain

     Lieut-Col Blakely, who had superseded Gen Stahel, passed by Lieut Thayer's station at 8 o'clock that morning and requested him to go on with the advance.  He accordingly abandoned the station, and moved with the advance cavalry through Frederick and accross the Monocacy.  At Urbana, four miles beyond the latter river, Col Blakely at 4 P.M. sent to Gen Howe his first dispatch.  It embraced no further information, and was the same in substance as Lieut Thayer's dispatch of 5:30 that morning.  Lieut Thayer found that from Urbana it was impossible to communicate with Maryland Heights, and he therefore thought it best to return with his detachment to Sandy Hook.  He reported to Gen Howe late that evening.  The general requested him to send out a party on the following morning to Sugar Loaf Mountain for the purpose of watching Edwards's and Conrad's Ferries.  With complance with his request, Lieut Thayer ordered Acting Sergt Franklin to proceed to Sugar Loaf Mountain on the 11th, and open communication with Maryland Heights.  Sergt Franklin narrowly escaped capture while in the vicinity of the mountain and returned to headquarters at 8 P.M.
     On the 12th, another party was sent out , under Lieut Kennedy, with a strong escort.  Lieut Kennedy succeeded in reaching the mountain, and opened communication with Lieut Thayer at 3 P.M.  He reported no enemy in sight.

     On the 13th, the stations remained as before, on Sugar Loaf Mountain and on Maryland Heights; but the station on Sugar Loaf failed to report any movement of importance.

     July 14h, Capt Town's detachment arrivedfrom West Virginia.  Lieut Thayer's party on Sugar Loaf was relieved by a detachment of Capt Town's command during the night, and ordered back to Harper's Ferry for the purpose of re-establishing the signal lines at that place.

     When the Confederates had been driven back from Washington and into Virginia, the detachnent established stations along the Upper Potomac at Williamsport, MD, at Fairview and Casey's Knob on the Blue Ridge, and at Greencastle in Pennsylvania, whence they could communicate by telegraph with Gen Couch at Harrisburg PA.  
These stations were so located as to command a view of all the considerable fords of the Potomac for the distance of fifty miles or more from Harper's Ferry westward.  Their orders were to keep close watch of any force moving toward, or threatening to cross, the Potomac into Maryland and to report immediately to the major-general in command at Harrisburg.

     During the late summer and fall of 1864, the detachment though small, consisting of the four officers and forty men already referred to, rendered as valuable and efficient service as could have been performed by a full regiment of cavalry.

     It was a scouting party of this detachment, led by Lieut Thayer, that first entered Chambersburg after it was burned by the Confederates in the summer of 1864, and gave authentic information of the route taken by the enemy on the retreat.

     Some long-range signalling was done by the officers of this department.  The stations were on an average fifteen miles apart, and in some instances they exchanged messages between stations that were thirty-five miles apart as a crow flies.  Maryland Heights, for instance, is thirty-five miles from Fairview, and over this course messages were sent and received accurately, by flag and torch, on several occasions.

     Dr Schmucker, in his Review of the Rebellion, says of these last attempts at invasion on the part of the Confederate leaders:  "The pressure upon the throat of the Rebellion began to be as severe as to be intolerable, but in vain Lee tried to shake it off.  In dispair he took advantage of a brief lull in Grant's activity, to send a few troops to join the irregular bands of northern and northwestern Virginia, in a raid upon Maryland and Pennsylvania, to threaten Washington, Baltimore and Philadelphia, in hope that, alarmed for the safety of the capital and northern cities, Grant might relax his hold; but he had mistaken this man.  Grant sent the 19th Corps, just ordered on from the Department of the Gulf, to the Shenandoah Valley, and reinforced it temporarily with the 6th Corps, which he could well spare, and as soon as parcticable nominated Sheridan for the command of the Army of the Shenandoah; but he himself did not relax the pressure upon Lee's lines for an hour.  Sheridan, after thoroughly reconnoitering his field, struck Early's Army a succession of fearful blows, sending him "whirling" through Winchester, on the 19th of September; driving him out of his strong position on Fisher's Hill, on the 22nd; pressing his pursuit up the valley, till Early's men were fain to take to the mountains; routing and forcing him back on the 8th and 12th of October; when, reinforced, he again ventured into battle with him, and on the 19th of October, sending him back in utter confusion, retreating twenty-six miles at night from the camp where, in the morning, he had fairly won a victory.

     "Early completely discomfited, Sheridan desolated as with the besom of destruction the fertile valley of the Shenandoah, and the adjacent Lray and Little Fort valleys, the inhabitants of all of which had sustained and encouraged the guerrillas in their acts of plundering and murdering unarmed Union men.

     "Lee found that this attempt to shake off his persistant adversary did not succeed.  He had, indeed, plundered a part of Maryland and southern Pennsylvania; and burned Chambersburg; and had brought off a large number of horses and cattle; but what had he gained?  Ewell's corps, or so much of it as Early had taken north, was almost destroyed, and the small remainder thoroughly demoralized.  He had lost some hundred cannon and thousands of small arms, the latter a very severe loss, as he could not replace them; the plunder Early brought into Virginia had most of it been recaptured. and the valley of the Shenandoah, his principle dependence for supplies, had been thoroughly stripped of its horses, cattle and grain."
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