XI Corps ( Union Army ) The XI Corps ( Eleventh Army Corps ) was a corps of the Union Army during the American Civil War , best remembered for its involvement in the battles of Chancellorsville and Gettysburg in 1863 . Formation and the Valley Campaign . The XI Corps was an amalgamation of two separate commands . These were John Fremont ' s Army of the Mountain Department and Louis Blenker ' s division of German immigrants . Blenker had led a German brigade at First Bull Run , although it was held in reserve and saw no major fighting , and afterwards became a division commander in the new Army of the Potomac . Intended to go to the Virginia Peninsula in the spring of 1862 , Blenker ' s troops were instead detached and sent out west to join Fremont . The combined command suffered a number of losses to Stonewall Jackson that spring in the Shenandoah Valley , and by the end of June was suffering severe shortages of supplies . Soldiers had not been paid in months and many were dropping from illness and straggling . Blenker himself was presently injured in a fall from his horse during the Northern Virginia Campaign in August and died a year later . On June 26 , 1862 , President Abraham Lincoln ordered that " the troops of the Mountain Department , heretofore under command of General John C . Frémont , shall constitute the First Army Corps , under the command of General Frémont . " The corps thus formed was , for the most part , the same as the one afterwards known as the XI Corps , and within a short time it was officially designated as such . This order of President Lincoln was included in the one constituting John Pope ' s Army of Virginia , which was formed from the three commands of Frémont , Nathaniel P . Banks , and Irvin McDowell . Frémont ' s troops had seen considerable service in western Virginia ( modern West Virginia ) , having fought hard in the Valley Campaign against Thomas J . " Stonewall " Jackson at McDowell and Cross Keys . Fremont refused to serve under John Pope ( whom he outranked ) and resigned . Major General Franz Sigel thus assumed command of the corps on June 29 . Many of the German soldiers could speak little English beyond " I fights mit Sigel " ( " I ' ll fight with Sigel " ) , which was their proud slogan . President Lincoln chose Sigel less for his military skills than his influence on this important political constituency . Sigel was in command at the Second Battle of Bull Run , where the corps encountered more hard fighting , losing 295 killed , 1 , 361 wounded , and 431 missing ; total , 2 , 087 . At this time the three divisions were commanded by Generals Robert C . Schenck , Adolph von Steinwehr , and Carl Schurz ( all with German - speaking skills ) ; there was also an independent brigade attached , under the command of Brig . Gen . Robert H . Milroy . By General Orders No . 129 , September 12 , 1862 , the corps ' s designation was changed to that of the XI Army Corps , a necessary change , as McDowell ' s command had resumed its original title of the I Corps . During the Maryland Campaign , and during the fall of 1862 , the XI Corps remained in Northern Virginia , in front of Washington , D . C . , occupying various outposts in the vicinity of Centreville . In December , it marched to Fredericksburg , but was not present at the battle , after which it went into winter quarters at Stafford , Virginia . Chancellorsville and Gettysburg . With the ascension of Joseph Hooker to command of the army in February 1863 , Franz Sigel was the second most senior officer in the ranks . Because of this and because the XI Corps was the smallest in the Army of the Potomac , he felt that it deserved to be enlarged . His request denied , Sigel angrily resigned his command . Replacing him was Maj . Gen Oliver Howard , who had lately been complaining that he deserved a corps command since General Daniel Sickles ( his junior in rank ) had gotten one . General Howard commanded the corps at Chancellorsville , May 1 – 3 1863 , at which time it numbered 12 , 169 effectives , and was composed of the divisions of Generals Charles Devens , von Steinwehr , and Schurz . It contained 27 regiments of infantry , of which 13 were German regiments . The men of the XI Corps were good soldiers , for the most part tried and veteran troops , but their leadership let them down . On May 1 , Robert E . Lee and his subordinate , " Stonewall " Jackson , came up with a risky , but daring , plan of attack . They would split their 40 , 000 - man force at Chancellorsville , with Jackson taking his Second Corps of 28 , 000 men around to attack the Union right flank . On May 2 , Jackson flawlessly executed his stealthy flanking march , whose target happened to be the unlucky XI Corps . The right flank of the Union line was not anchored to any geographic barrier , such as a river or mountain ; the flank was " in the air " . Although General Howard had been warned of Confederate movement across his front , he took no steps to prepare his command against Jackson ' s attack ; there only were two unmanned artillery pieces pointed at the Wilderness . When Jackson ' s corps struck at about 6 p . m . , the XI Corps was completely unprepared , many of the men engaged in eating supper . The attack was a complete success and the high point of Jackson ' s military career , but it was an utter disaster for the XI Corps . Some of the brigades were able to change front to meet the attack , and made a gallant resistance for over an hour , seriously retarding the enemy ' s onset , after which they retired slowly and in good order . The loss to the corps at Chancellorsville was 217 killed , 1 , 218 wounded , and 972 captured or missing ; total , 2 , 407 . At Gettysburg the corps was still under the command of Howard ; the divisions were under Generals Francis C . Barlow , Steinwehr , and Schurz , and contained 26 regiments of infantry and 5 batteries of artillery . The men of the Corps went into this battle with high anticipation and hopes that they could restore the reputation sullied at Chancellorsville . They arrived from south of town mid - day on July 1 , 1863 , aware that the I Corps was already heavily engaged just to the west of town . General Howard deployed one division ( von Steinwehr ' s ) on the heights of Cemetery Hill , as a reserve , and the other two divisions north of town . Howard briefly commanded the entire battle until the arrival of Winfield S . Hancock . The Confederate Second Corps under Richard S . Ewell arrived from the north with a devastating assault . Barlow ' s division was deployed on the right and he foolishly moved his force to a small hill ( that is now known as Barlow ' s Knoll ) , causing a salient in the line that could be attacked from multiple directions . The division of Jubal A . Early took advantage of this and Barlow ' s division reeled back . Barlow himself was wounded and captured . The collapse of the corps right flank had a domino effect on its left and on the I Corps division to its left , resulting in a general retreat of Union forces through the town of Gettysburg to the safety of Cemetery Hill , losing many captured on the way . On the second day , the XI Corps participated in the gallant and successful defense of East Cemetery Hill against a second attack by Early . On the day before the battle of Gettysburg , the corps reported 10 , 576 officers and men for duty ; its loss in that battle was 368 killed , 1 , 922 wounded , and 1 , 511 captured or missing ; total , 3 , 801 , out of less than 9 , 000 engaged . Tennessee . Returning to Virginia after Gettysburg , on August 7 the 1st Division ( Alexander Schimmelfennig ' s and later George Henry Gordon ' s ) was permanently detached , having been ordered to Charleston Harbor . On the September 24 , the 2nd and 3rd divisions ( Steinwehr ' s and Schurz ' s ) were ordered to Tennessee , together with the XII Corps . These two corps , numbering over 20 , 000 men , were transported , within a week , over 1 , 200 miles , and placed on the banks of the Tennessee River , at Bridgeport , without an accident or detention . During the following month , on October 29 , Howard ' s two divisions were ordered to the support of the XII Corps , in the midnight Battle of Wauhatchie , opening the supply lines to the besieged city of Chattanooga . Arriving there , Col . Orland Smith ' s Brigade of von Steinwehr ' s Division charged up a steep hill in the face of the enemy , receiving but not returning the fire , and drove James Longstreet ' s veterans out of their entrenchments , using the bayonet alone . Some of the regiments in this affair suffered a severe loss , but their extraordinary gallantry won extravagant expressions of praise from various generals , high in rank , including General Ulysses S . Grant . A part of the XI Corps was also actively engaged at Missionary Ridge , where it cooperated with William T . Sherman ' s forces on the left . After this battle it was ordered to East Tennessee for the relief of Knoxville , a campaign whose hardships and privations exceeded anything within the previous experience of the command . In April , 1864 , the two divisions of the XI Corps were broken up and transferred to the newly formed XX Corps . General Howard was transferred to the command of the IV Corps , and , subsequently , was promoted to the command of the Army of the Tennessee . Command history . * Corps assigned to the Army of the Cumberland ; other entries assigned to the Army of the Potomac