Editing Lew Wallace (section)

==Civil War service==
Wallace, a staunch supporter of the Union, became a member of the [[Republican party (United States)|Republican party]],<ref name=Forbes388/> and began his full-time military career soon after the Confederate attack on [[Fort Sumter]], [[South Carolina]], on April 12, 1861. Indiana's governor, the Republican [[Oliver P. Morton]], asked Wallace to help recruit Indiana volunteers for the Union army.<ref>Morsberger and Morseberger, p. 54.</ref> Wallace, who also sought a military command, agreed to become the state's [[Indiana Adjutant General|adjutant general]] on the condition that he would be given command of a regiment of his choice.<ref name="swansburg20130326">{{cite web| url=http://www.slate.com/articles/life/history/2013/03/ben_hur_and_lew_wallace_how_the_scapegoat_of_shiloh_became_one_of_the_best.single.html |title=The Passion of Lew Wallace |work=Slate |date=March 26, 2013 |access-date=March 30, 2013 |author=Swansburg, John}}</ref><ref>Stephens, pp. 17–18.</ref> Indiana's quota of six regimental units was filled within a week,<ref>Boomhower, pp. 2, 47.</ref> and Wallace took command of the [[11th Indiana Infantry Regiment|11th Indiana Volunteer Infantry Regiment]], which was mustered into the Union army on April 25, 1861. Wallace received his formal commission as a [[Colonel (United States)|colonel]] in the Union army the following day.<ref name=Eicher551/><ref name=Morrow9/><ref>Stephens, p. 19.</ref>

On June 5, 1861, Wallace went with the 11th Indiana to [[Cumberland, Maryland]], and on June 12, the regiment won a minor battle at [[Romney, West Virginia|Romney]], [[Virginia]], (in present-day [[West Virginia]]).<ref name=Morrow9/><ref>It was misdated on Wallace's official report. See Stephens, p. 24.</ref>{{r|swansburg20130326}} The rout boosted morale for Union troops and led to the Confederate evacuation of [[Harpers Ferry, West Virginia|Harpers Ferry]] on June 18.<ref>Stephens, p. 27.</ref> On September 3, 1861, Wallace was promoted to [[Brigadier general (United States)|brigadier general]] of [[United States Volunteers|U.S. Army volunteers]] and given command of a brigade.<ref name=Eicher551/>

===Forts Henry and Donelson===
{{Main|Battle of Fort Henry|Battle of Fort Donelson}}
On February 4 and 5, 1862, prior to the advance against [[Fort Henry (site of the Battle of Fort Henry)|Fort Henry]], Union troops under the command of Brig. Gen. [[Ulysses S. Grant]] and a flotilla of Union ironclads and [[timberclad warship|timberclad]] gunboats under the command of Flag Officer [[Andrew Hull Foote]] made their way toward the Confederate fort along the [[Tennessee River]] in western [[Tennessee]]. Wallace's brigade, which was attached to Brig. Gen. [[Charles Ferguson Smith|Charles F. Smith]]'s division, was ordered to occupy Fort Heiman, an uncompleted Confederate fort across the river from Fort Henry. Wallace's troops secured the deserted fort and watched the Union attack on Fort Henry from their hilltop position. On February 6, after more than an hour of bombardment from the Union gunboats, Confederate Brig. Gen. [[Lloyd Tilghman]] surrendered Fort Henry to Foote.<ref name=Stephens45-47>Stephens, pp. 45–47.</ref>

[[File:Fort Donelson Feb15pm.png|thumb|left|200px|Map showing Wallace's counterattack at [[Fort Donelson]] (1862)]]
Grant's superior, Maj. Gen. [[Henry W. Halleck]], was concerned that Confederate reinforcements would try to retake the two forts when the Union troops moved overland toward [[Fort Donelson]], so Wallace was left in command at Fort Henry to keep the forts secure.<ref name=Boom50>Boomhower, 50.</ref><ref>Ferraro, p. 127.</ref> Displeased to have been left behind,{{r|swansburg20130326}} Wallace prepared his troops to move out at a moment's notice. The order came at midnight on February 13. Wallace arrived in front of Fort Donelson the following day and was placed in charge of the newly-forming 3rd [[division (military)|Division]]. Many of the men in the division were untested reinforcements.<ref>Stephens, p. 48.</ref> Wallace's three brigades took up position in the center of the Union line, facing Fort Donelson.<ref name=Boom50/>

During the fierce Confederate assault on February 15, and with Grant's absence from the battlefield, Wallace acted on his own initiative to send Cruft's brigade to reinforce the beleaguered division of Brig. Gen. [[John A. McClernand]], despite orders from Grant to hold his position and prevent the enemy from escaping and without Grant's authority to take the offensive.<ref>Boomhower, p. 51.</ref><ref>Grant later approved of Wallace's actions. See Ferraro, p. 127.</ref> With the Confederates continuing to advance, Wallace led a second brigade to the right and engaged the Confederates with infantry and artillery. Wallace's decision stopped their forward movement and was key in stabilizing a defensive line for the Union troops. After the Confederate assault had been checked, Wallace led a counterattack that regained the lost ground on the Union right.<ref>Stephens, p. 62; Ferraro, p. 127.</ref> On March 21, 1862, McClernand, C. F. Smith, and Wallace were promoted to [[Major general (United States)|major general]] in that order for their efforts.<ref name=Eicher773>Eicher, p. 773.</ref> Wallace, who was age thirty-four at the time of his promotion, became the youngest major general in the Union army.<ref>Stephens, pp. 67–68; Boomhower, p. 53.</ref>

===Shiloh===
{{Main|Battle of Shiloh}}
[[File:Shiloh Battle April 6 pm.png|thumb|200px|Map of the Battle of Shiloh, afternoon of April 6, 1862]]
Wallace's most controversial command came at the [[battle of Shiloh]], where he continued as the 3rd Division commander under Maj. Gen. Grant. What was to become a long-standing controversy developed around the contents of Wallace's written orders on April 6, the 3rd Division's movements on the first day of battle, and its late arrival on the field.<ref>Ferraro, p. 129; Stephens, p. 84.</ref> The next day, the reinforcement by Wallace's division and the juncture of Maj. Gen. [[Don Carlos Buell]]'s Army of the Ohio permitted the Union forces to push back the enemy all day long to gain the victory.<ref>Boomhower, p. 7.</ref>

Prior to the battle, Wallace's division had been detached and was encamped near Crump's Landing, five miles downstream from Pittsburg Landing and the bulk of Grant's army. Wallace's orders were to guard the Union's rear and to cover the road leading west to Bethel Station, Tennessee, where railroad lines led to [[Corinth, Mississippi]], {{convert|20|mi|km}} to the south.<ref>Stephens, pp. 65, 72; Ferraro, p. 128.</ref> To protect the road from Crump's Landing and Bethel Station, Wallace sent Col. [[John Milton Thayer|John M. Thayer]]'s 2nd Brigade to Stoney Lonesome, {{convert|3|mi|km}} west of Crump's Landing, and the 3rd Brigade, commanded by Col. Charles Whittlesey to [[Adamsville, Tennessee|Adamsville]], {{convert|5.5|mi|km}} west of Crump's Landing. Col. [[Morgan Lewis Smith|Morgan L. Smith]]'s 1st Brigade remained with Wallace at Crump's Landing, {{convert|5|mi|km}} north of [[Pittsburg Landing, Tennessee]].<ref>Stephens, p. 76.</ref>

Around 5 a.m. on April 6, 1862, the Battle of Shiloh began in which Grant's army at Pittsburg Landing was surprised and began to be pushed back by a sudden attack from the [[Confederate States Army|Confederate army]] under Gen. [[Albert Sidney Johnston]]. Grant, who heard the early morning artillery fire, took a steamboat upriver from his headquarters at [[Savannah, Tennessee]], briefly stopping at Crump's Landing, where he gave Wallace orders to wait, but be ready to move in any direction. Grant proceeded to Pittsburg Landing, where he arrived around 9:00 or 9:30&nbsp;a.m.<ref>Stephens, p. 83; Ferraro, p. 129.</ref> Grant's new orders to Wallace, which arrived between 11 and 11:30&nbsp;a.m., were given verbally to Grant's quartermaster, who transcribed them before they were delivered.<ref>Stephens, pp. 83–84; Boomhower, pp. 58–59.</ref> The written orders were lost during the battle, so their exact wording cannot be confirmed; however, most eyewitness accounts agree that Grant ordered Wallace to join the right side of the Union army, presumably in support of Brig. Gen. [[William Tecumseh Sherman]]'s 5th Division, which was encamped near Shiloh Church on the morning of April 6.<ref>Stephens, pp. 71, 84–85.</ref>

Knowledge of the area's roads played a critical role in Wallace's journey to the battlefield on April 6. In late March, after heavy rains made transportation difficult between Crump's Landing and Pittsburg Landing, Wallace's men had opened a route to Pittsburg Landing along [[shunpiking|Shunpike]] road, which connected to a road near Sherman's camp. Brig. Gen. [[W. H. L. Wallace]]'s men at Pittsburg Landing opened the River Road (also known as the Hamburg-Savannah Road), a route farther east.<ref>Stephens, pp. 72, 74.</ref>

Of the two main routes that Wallace could use to move his men to the front, he chose the Shunpike road, the more direct route to reach the right of Sherman's division near Shiloh Church.<ref>Stephens, p. 86; Boomhower, p. 60.</ref> The day before the battle, Wallace wrote a letter to  W. H. L. Wallace, recommending this route to reinforce the 3rd Division.<ref>Stephens, p. 75.</ref> Lew Wallace and his staff maintained after the battle that Grant's order did not specify Pittsburg Landing as their destination, and that it did not specify which route the 3rd Division was ordered to take. However, Grant claimed in his memoirs that he had ordered Wallace to take the route nearest to the river to reach Pittsburg Landing.<ref>Stephens, p. 85; Boomhower, pp. 59–60.</ref><ref>Grant, v. I, pp. 336–337.</ref> Historians are divided, with some stating that Wallace's explanation is the most logical.{{r|swansburg20130326}}

After a second messenger from Grant arrived around noon with word to move out, Wallace's division of approximately 5,800 men began their march toward the battlefield.<ref>Stephens, pp. 82, 87.</ref> Between 2 and 2:30&nbsp;p.m., Colonel [[William R. Rowley]], sent by Grant, rode to where Wallace's division first was; there was only a supply wagon departing the scene. Riding on further, Rowley found Wallace along the Shunpike road at the head of his column near Clear Creek, positioned on high ground. He informed Wallace that Sherman had been forced back from Shiloh Church and was fighting closer to the river, near Pittsburg Landing. Grant had ordered Rowley to "tell him to come up at once" and that "if he should require a written order of you, you will give it to him at once".<ref>Stephens, pp. 87–88; Boomhower, pp. 60–61.</ref><ref>[[Lew Wallace#richardson|Richardson, 1885]] p. 243</ref> Rowley pulled Wallace off to the side and warned him of the danger that lay just ahead, exclaiming, "Don't you know that Sherman has been driven back? Why, the whole army is within half a mile of the river, and it's a question if we are not all going to be driven into it." Wallace, stunned by the news, sent his cavalry ahead to assess the situation, and upon returning, it had confirmed Rowley's claim.<ref>[[Lew Wallace#groom|Groom, 2012]], p. 305</ref> The Union army had been pushed back so far that Wallace was heading toward the rear of the advancing Southern troops.{{r|swansburg20130326}}

Wallace briefly considered attacking the Confederates, but abandoned the idea. Instead he made a controversial decision to countermarch his first two brigades along the Shunpike road, follow a crossroads to the River Road, and then move south to Pittsburg Landing. Rather than realigning his troops, so that the rear guard would be in the front, Wallace countermarched his column to maintain their original order, keeping his artillery in position to support the Union infantry on the field.<ref>Boomhower, p. 61.</ref> After the time-consuming maneuver was completed, Wallace's troops returned to the midpoint on the Shunpike road, crossed east over a path to the River Road, and followed it south to join Grant's army on the field. Progress was slow due to the atrocious road conditions and the countermarch. Wallace's division arrived at Pittsburg Landing about 6:30&nbsp;p.m., after having marched about {{convert|14|mi|km}} in nearly seven hours over roads that had been left in terrible conditions by recent rainstorms and previous Union marches. They gathered at the battlefield at dusk, about 7 p.m., with the fighting basically over for the day, and took up a position on the right of the Union line.<ref>Stephens, pp. 80, 90–91.</ref>

[[File:Shiloh Battle April 7.png|thumb|200px|Map of the Battle of Shiloh, April 7, 1862]]
The next day, April 7, Wallace's division held the extreme right of the Union line. Two of Wallace's batteries with the aid of a battery from the 1st Illinois Light Artillery were the first to attack at about 5:30&nbsp;a.m.<ref>Stephens, pp. 93, 95.</ref><ref>"The March of Lew Wallace's Division to Shiloh." In [http://ehistory.osu.edu/osu/books/battles/index.cfm ''Battles and Leaders of the Civil War''], vol. 1, edited by Robert Underwood Johnson and Clarence C. Buel. New York: Century Co., 1884–1888. pp. 608–610. {{OCLC|2048818}}. (Johnson and Buel list no author for this article, but indicate it was based on material from Wallace.)</ref> Sherman's and Wallace's troops helped force the Confederates to fall back, and by 3 p.m. the Confederates were retreating southwest, toward Corinth.<ref>Stephens, pp. 95–100.</ref>

Historian Timothy B. Smith noted that on the second day Wallace's division sustained far fewer casualties (296) than any of Buell's three divisions. The number of casualties does not always show the effectiveness of troops. Wallace had his soldiers lie down when they were under fire, which minimized casualties. He also maneuvered his division so that it repeatedly turned the Confederate left flank.{{sfn|Smith|2014|pp=347–348}} Wallace advanced his division at 6:30 am, reached the south side of Tilghman Branch about 8:00 am, and occupied a commanding ridge by 9:00 am, all with little opposition. Here he paused to wait for Union troops to appear on his left. Up to this point, Wallace's movements were slow.{{sfn|Smith|2014|pp=254–257}} Once Grant's and Buell's soldiers reached the Confederate main line of defense they were stopped in heavy fighting. Noting that the Confederate left did not reach as far as Owl Creek, Wallace wheeled his division to outflank the enemy line. Finding Wallace's troops to their left and rear, the left-hand Confederate brigade hurriedly fell back. This unhinged the entire line and the Confederate troops soon retreated to a second position around noon.{{sfn|Smith|2014|pp=362–365}} At around 1:00 pm, Wallace worked a few regiments around the Confederate left flank, forcing their withdrawal to a third position.{{sfn|Smith|2014|pp=380–381}} After the Confederates left the battlefield, Wallace's division went the farthest south of the Union forces, but he pulled his troops back before going into camp that evening.{{sfn|Smith|2014|p=393}}

===Shiloh controversy===
[[File:Lew Wallace (ca. 1865).jpg|thumb|Maj. Gen. Lew Wallace]]
At first, the battle was viewed by the [[Northern United States|North]] as a victory; however, on April 23, after civilians began hearing news of the surprise and resulting high number of casualties, the Lincoln administration asked the Union army for further explanation.<ref>Stephens, pp. 105–106, and Boomhower, pp. 64–65.</ref> Grant, who was accused of poor leadership at Shiloh, and his superior, Halleck, tried to place the blame on Wallace by asserting that his failure to follow orders and the delay in moving up his division on April 6 had nearly cost the Union the battle.<ref name=Stephens107-8>Stephens, pp. 107–108.</ref>

After hearing reports that Wallace refused to obey anything but ''written'' orders, an angry General Grant asserted that a division general "ought to take his troops to wherever the firing may be, even without orders".<ref>[[#timothy|Smith, Timothy, 2013]] pp. 90–91</ref>

On April 30, 1862, Halleck reorganized his army and removed Wallace and John McClernand from the front lines, placing both of them in reserve, with McClernand commanding.<ref>Stephens, p. 112; Morrow, p. 10.</ref>

Wallace's reputation and career as a military leader suffered a significant setback from controversy over Shiloh.<ref name=Morrow9/> He spent the remainder of his life trying to resolve the accusations and change public opinion about his role in the battle.<ref name=Stephens107-8/> On March 14, 1863, Wallace wrote a letter to Halleck that provided an official explanation of his actions. He also wrote Grant several letters and met with him in person more than once in an attempt to vindicate himself. On August 16, 1863, Wallace wrote Sherman for advice on the issue. Sherman urged Wallace to be patient and not to request a formal inquiry. Although Sherman brought Wallace's concerns to Grant's attention, Wallace was not given another active duty command until March 1864.<ref>Ferraro, pp. 131–134, 138, 145.</ref>

For many years Grant stood by his original version of the orders to Wallace. As late as 1884, when Grant wrote an article on Shiloh for ''[[The Century Magazine]]'' that appeared in its February 1885 issue, he maintained that Wallace had taken the wrong road on the first day of battle.<ref>Ferraro, p. 146.</ref> After W. H. L. Wallace's widow gave Grant a letter that Lew Wallace had written to her husband the day before the battle (the one indicating his plans to use the Shunpike road to pass between Shiloh and his position west of Crump's Landing), Grant changed his mind.<ref name=Stephens232>Stephens, p. 232.</ref><ref name=Ferraro147>Ferraro, p. 147.</ref> Grant wrote a letter to the editors at ''Century'', which was published in its September 1885 issue, and added a note to his memoirs to explain that Wallace's letter "modifies very materially what I have said, and what has been said by others, about the conduct of General Lew Wallace at the battle of Shiloh."<ref name=Ferraro147 /> While reaffirming that he had ordered Wallace to take the River Road, Grant stated that he could not be sure the exact content of Wallace's written orders, since his verbal orders were given to one of his aides and transcribed.<ref name="Stephens232" /><ref name=Grant>Grant, v. I, pp. 351–352.</ref>

Grant's article in the February 1885 issue of ''Century'' became the basis of his chapter on Shiloh in his memoirs, which were published in 1886, and influenced many later accounts of Wallace's actions on the first day of battle.<ref name=Ferraro147 /> Grant acknowledged in his memoirs: "If the position of our front had not changed, the road which Wallace took would have been somewhat shorter to our right than the River road."<ref name=Grant /> Wallace's account of the events appeared in his autobiography, which was published posthumously in 1906.<ref>Ferraro, p. 148.</ref> Despite his later fame and fortune as the writer of ''Ben-Hur'', Wallace continued to lament, "Shiloh and its slanders! Will the world ever acquit me of them? If I were guilty I would not feel them as keenly."{{r|swansburg20130326}}

===The Kentucky Campaign and Defense of Cincinnati===
{{Main|Defense of Cincinnati}}
Following his loss of a field command, Wallace returned to Indiana and spent time at his retreat on the Kankakee River. It was there that he received a telegram from Governor Morton to take command of an Indiana regiment in the [[Department of the Ohio]] to help with the defense of Kentucky during [[Braxton Bragg]]'s incursion into [[Kentucky]] and to report to Louisville. Presenting himself with his new regiment to Brig. Gen. [[Jeremiah Boyle]]<ref>Boyle was then Military Governor Kentucky.</ref> in Louisville, Boyle was uncomfortable having a superior officer under his command. Boyle ordered Wallace to take his regiment to Lexington, take command of the hastily created [[Army of Kentucky]], and march to the relief of the men at Cumberland Gap. Wallace began a defensive plan that would place his army on the north side of the Kentucky River, about 15 miles from [[Boonesboro, Kentucky|Boonesboro]] to defend against the advance of Gen. [[Edmund Kirby Smith]]'s army from the direction of [[Cumberland Gap]]. He had all of the locks on the river in the area opened to flood the fords, confiscated every boat in the area and moved them to the north bank, and the position was secured by sheer limestone cliffs on his flanks. But Wallace was soon relieved of command by Maj. Gen. [[William "Bull" Nelson]], who took command of the Army of Kentucky on August 24 on orders from Wright. Nelson altered Wallace's defensive plan, and engaged Smith's [[Confederate Army of Kentucky]] at the [[Battle of Richmond]] on August 30, and was soundly defeated.

Wallace and his staff started a return to Cincinnati to await any orders. Maj. Gen. [[Horatio Wright]] sent a telegram ordering Wallace to return to Lexington to take command of what remained of the Army of Kentucky. Traveling by train from Cincinnati, Wallace received another telegram from Wright when he arrived at [[Paris, Kentucky]], ordering him to remain in Cincinnati. He immediately returned to Cincinnati and began vigorous efforts for the [[defense of Cincinnati]].

Upon his arrival in the city, Wallace immediately began organizing the defenses of Cincinnati, Ohio and the Kentucky cities of [[Covington, Kentucky|Covington]] and [[Newport, Kentucky|Newport]] south of Cincinnati. Wallace ordered martial law, set a strict curfew, closed all businesses, and began putting male citizens to work on rifle pits, felling trees for makeshift [[abatis]] and clear fields of fire, and improving the 1861 earthwork defenses. It was during this hasty defensive preparation that the [[Black Brigade of Cincinnati]] was formed, by Wallace's orders.

In response to calls from Ohio's Governor Tod, approximately 15,000 so-called "Squirrel Hunters"—untrained volunteers who carried outdated equipment—reported to Cincinnati. Additionally, newly-created regiments from Indiana and Ohio were rushed to Cincinnati; most had not completed their training.

Because the arriving regiments could not be ferried quickly enough across the Ohio River, Wallace ordered the construction of a pontoon bridge, which was constructed using coal barges in under 48 hours.

While at Lexington, Gen. Smith gave Brig. Gen. [[Henry Heth]] permission to make a "demonstration" on Cincinnati, granting him approximately 8,000 men. Heth moved within a few miles of Fort Mitchell and exchanged skirmish fire with men from the [[101st Ohio Infantry]], [[103rd Ohio Infantry]], and [[104th Ohio Infantry]] on September 10–11, then returned to Lexington on September 12, 1862.

Wallace's leadership during the defense of Cincinnati earned him the nickname by local newspapers as the "Savior of Cincinnati". On September 12, Wallace telegraphed Wright from Cincinnati: "The skedaddle is complete; every sign of a rout. If you say so I will organize a column of 20,000 men to pursue to-night." Instead, Wright relieved Wallace of a field command.

===Other military assignments===
Wallace was ordered to take command of [[Camp Chase]], a prisoner-of-war camp at [[Columbus, Ohio]], where he remained until October 30, 1862. His instructions there were to recruit and train Confederate prisoners of war for U.S. Army service (also known as "Galvanized Yankees") to aid in the [[Dakota War of 1862|Sioux Uprising]]. The [[Battle of Wood Lake]] on September 23 essentially ended the uprising and Wallace was again without a command.

The following month, Wallace was placed in charge of the five-member commission [[Buell Military Commission]] to investigate Maj. Gen. [[Don Carlos Buell]]'s conduct in response to the Confederate invasion of Kentucky. The commission criticized Buell for his retreat, but it did not find him disloyal to the Union. When the commission's work was completed on May 6, 1863, Wallace returned to Indiana to wait for a new command.<ref>Stephens, pp. 127, 137–146.</ref> In mid-July 1863, while Wallace was home, he helped protect the railroad junction at [[North Vernon, Indiana]], from Confederate general [[Morgan's Raid|John Hunt Morgan's raid]] into southern Indiana.<ref>Stephens, pp. 153–156.</ref>

===Monocacy===
{{Main|Battle of Monocacy}}
Wallace's most notable service came on Saturday, July 9, 1864, at the [[Battle of Monocacy]] part of the [[Valley Campaigns of 1864]]. Although Confederate General [[Jubal A. Early]] and an estimated 15,000 troops defeated Wallace's troops at Monocacy Junction, Maryland, forcing them to retreat to Baltimore, the effort cost Early a chance to capture [[Washington, D.C.]]<ref>Boomhower, p. 8.</ref> Wallace's men were able to delay the Confederate advance toward Washington for an entire day, giving the city time to organize its defenses. Early arrived in Washington at around noon on July 11, two days after defeating Wallace at Monocacy, the northernmost Confederate victory of the war,<ref>Kennedy, p. 308.</ref> but Union reinforcements had already arrived at [[Battle of Fort Stevens|Fort Stevens]] to repel the Confederates and force their retreat to Virginia.<ref>Kennedy, p. 305; Stephens, p. 204.</ref>

Wallace, who had returned to active duty on March 12, 1864, assumed command of [[VIII Corps (Union Army)|VIII Corps]], which was headquartered in [[Baltimore, Maryland|Baltimore]].<ref>Stephens, pp. 161–162, 164, 175; Boomhower, pp. 8, 69.</ref> On July 9, a combined Union force of approximately 5,800 men under Wallace's command (mostly hundred-days' men from VIII Corps) and a division under [[James B. Ricketts]] from [[VI Corps (Union Army)|VI Corps]] encountered Confederate troops at Monocacy Junction between 9 and 10 a.m.<ref>Stephens, p. 192.</ref> Although Wallace was uncertain whether Baltimore or Washington, D.C., was the Confederate objective, he knew his troops would have to delay the advance until Union reinforcements arrived.<ref>Stephens, pp. 185–186.</ref> Wallace's men repelled the Confederate attacks for more than six hours before retreating to Baltimore.<ref>Boomhower, p. 73; Stephens, pp. 196, 200.</ref><ref>Kennedy, p. 305.</ref>

After the battle Wallace informed Halleck that his forces fought until 5 p.m., but the Confederate troops, which he estimated at 20,000 men, had overwhelmed them. When Grant learned of the defeat, he named Maj. Gen. [[Edward Ord|E. O. C. Ord]] as Wallace's replacement in command of VIII Corps. On July 28, after officials learned how Wallace's efforts at Monocacy helped save Washington D.C. from capture, he was reinstated as commander of VIII Corps.<ref>Stephens, pp. 201, 203, 205; Boomhower, p. 74.</ref> In [[Personal Memoirs of Ulysses S. Grant|Grant's memoirs]], he praised Wallace's delaying tactics at Monocacy:

<blockquote>If Early had been but one day earlier, he might have entered the capital before the arrival of the reinforcements I had sent.&nbsp;... General Wallace contributed on this occasion by the defeat of the troops under him, a greater benefit to the cause than often falls to the lot of a commander of an equal force to render by means of a victory.<ref>Grant, [http://www.bartleby.com/1011/57.html Chapter LVII, p. 13.]</ref></blockquote>

===Later military service===
On January 22, 1865, Grant ordered Wallace to the [[Rio Grande]] in southern [[Texas]] to investigate Confederate military operations in the area. Although Wallace was not officially authorized to offer terms, he did discuss proposals for the surrender of the Confederate troops in the [[Trans-Mississippi Department]]. Wallace provided Grant with copies of his proposals and reported on the negotiations, but no agreement was made. Before returning to Baltimore, Wallace also met with Mexican military leaders to discuss the U.S. government's unofficial efforts to aid in expelling [[Maximilian I of Mexico|Maximilian's]] French occupation forces from Mexico.<ref>Stephens, pp. 212–217.</ref>

Following President Lincoln's death on April 15, 1865, Wallace was appointed to the military commission that investigated the [[Abraham Lincoln assassination|Lincoln assassination conspirators]]. The commission, which began in May, was dissolved on June 30, 1865, after all eight conspirators were found guilty.<ref>Stephens, pp. 219, 221–222; Morrow, p. 11.</ref> In mid-August 1865, Wallace was appointed head of an eight-member military commission that investigated the conduct of [[Henry Wirz]], the Confederate commandant in charge of the South's [[Andersonville prison camp]]. The [[court-martial]] which took nearly two months, opened on August 21, 1865. At its conclusion Wirz was found guilty and sentenced to death.<ref name=Eicher551/><ref>Stephens, pp. 223, 226;  Boomhower, pp. 85–87.</ref>

On April 30, 1865, Wallace had accepted an offer to become a major general in the Mexican army, but the agreement, which was contingent upon his resignation from the U.S. Army, was delayed by Wallace's service on the two military commissions. Wallace tendered his resignation from the U.S. Army on November 4, 1865, effective November 30,<ref name=Eicher773 /><ref>Stephens, p. 227.</ref> and returned to Mexico to assist the Mexican army. Although the [[Benito Juárez|Juárez]] government promised Wallace $100,000 for his services, he returned to the United States in 1867 in deep financial debt.<ref>Morrow, p. 12.</ref><ref>Wallace received $15,000 from the Mexican government in 1882. See Stephens, pp. 215–217, 229.</ref>

After the war, Wallace became a companion of the Indiana Commandery of the [[Military Order of the Loyal Legion of the United States]].