Battle of Missionary Ridge The Battle of Missionary Ridge was fought November 25 , 1863 , as part of the Chattanooga Campaign of the American Civil War . Following the Union victory in the Battle of Lookout Mountain on November 24 , Union forces under Maj . Gen . Ulysses S . Grant assaulted Missionary Ridge and defeated the Confederate Army of Tennessee , commanded by Gen . Braxton Bragg . In the morning , elements of the Army of the Tennessee commanded by Maj . Gen . William T . Sherman attempted to capture the northern end of Missionary Ridge , Tunnel Hill , but were stopped by fierce resistance from the Confederate divisions of Maj . Gen . Patrick R . Cleburne , William H . T . Walker , and Carter L . Stevenson . In the afternoon , Grant was concerned that Bragg was reinforcing his right flank at Sherman ' s expense . He ordered the Army of the Cumberland , commanded by Maj . Gen . George H . Thomas , to move forward and seize the Confederate line of rifle pits on the valley floor , and stop there to await further orders . The Union soldiers moved forward and quickly pushed the Confederates from the first line of rifle pits but were then subjected to a punishing fire from the Confederate lines up the ridge . At this point , the Union soldiers continued the attack against the remaining lines , seeking refuge near the crest of the ridge ( the top line of rifle pits were sited on the actual crest rather than the military crest of the ridge , leaving blind spots ) . This second advance was taken up by the commanders on the spot , but also by some of the soldiers who , on their own , sought shelter from the fire further up the slope . The Union advance was disorganized but effective ; finally overwhelming and scattering what ought to have been , as General Grant himself believed , an impregnable Confederate line . In combination with an advance from the southern end of the ridge by divisions under Maj . Gen . Joseph Hooker , the Union Army routed Bragg ' s army , which retreated to Dalton , Georgia , ending the siege of Union forces in Chattanooga , Tennessee . Background . After their disastrous defeat at the Battle of Chickamauga , the 40 , 000 men of the Union Army of the Cumberland under Maj . Gen . William Rosecrans retreated to Chattanooga . Confederate General Braxton Bragg ' s Army of Tennessee besieged the city , threatening to starve the Union forces into surrender . Bragg ' s troops established themselves on Missionary Ridge and Lookout Mountain , both of which had excellent views of the city , the Tennessee River flowing through the city , and the Union ' s supply lines . The only supply line that was not controlled by the Confederates was a roundabout , tortuous course nearly 60 miles long over Walden ' s Ridge from Bridgeport , Alabama . Heavy rains began to fall in late September , washing away long stretches of the mountain roads . On October 1 , Maj . Gen . Joseph Wheeler ' s Confederate cavalry intercepted and severely damaged a train of 800 wagons — burning hundreds of the wagons , and shooting or sabering hundreds of mules — at the start of his October 1863 Raid through Tennessee to sever Rosecrans ' s supply line . Toward the end of October , Federal soldiers ' rations were " four cakes of hard bread and a quarter pound of pork " every three days . The Union Army sent reinforcements : Maj . Gen . Joseph Hooker with 15 , 000 men in two corps from the Army of the Potomac in Virginia and Maj . Gen . William T . Sherman with 20 , 000 men from Vicksburg , Mississippi . On October 17 , Maj . Gen . Ulysses S . Grant received command of the Western armies , designated the Military Division of the Mississippi ; he moved to reinforce Chattanooga and replaced Rosecrans with Maj . Gen . George H . Thomas . Thomas launched a surprise amphibious landing at Brown ' s Ferry on October 27 that opened the Tennessee River by linking up his Army of the Cumberland with Hooker ' s relief column southwest of the city , thus allowing supplies and reinforcements to flow into Chattanooga over what was called the " Cracker Line " . In response , Bragg ordered Lt . Gen . James Longstreet to force the Federals out of Lookout Valley . The ensuing Battle of Wauhatchie ( October 28 – 29 ) was one of the war ' s few battles fought exclusively at night . The Confederates were repulsed , and the Cracker Line was secured . Sherman arrived with his 20 , 000 men of the Army of the Tennessee in mid - November . Grant , Sherman , and Thomas planned a double envelopment of Bragg ' s force , with the main attack by Sherman against the northern end of Missionary Ridge , supported by Thomas in the center and by Hooker , who would capture Lookout Mountain and then move across the Chattanooga Valley to Rossville , Georgia , and cut off the Confederate retreat route to the south . On November 23 , Sherman ' s force was ready to cross the Tennessee River . Grant ordered Thomas to advance halfway to Missionary Ridge on a reconnaissance in force to determine the strength of the Confederate line , hoping to ensure that Bragg would not withdraw his forces and move in the direction of Knoxville , Tennessee , where Maj . Gen . Ambrose Burnside was being threatened by a Confederate force under Lt . Gen . James Longstreet . Thomas sent over 14 , 000 men toward a minor hill named Orchard Knob and overran the Confederate defenders . Grant changed his orders and instructed Thomas ' s men to dig in and hold the position . Surprised by Thomas ' s move and realizing that his center and right might be more vulnerable than he had thought , Bragg quickly readjusted his strategy . Bragg assigned Col . Warren Grigsby ' s brigade of Kentucky cavalry to picket the Tennessee river northeast of Chattanooga and ordered Brig . Gen . Marcus Joseph Wright to bring his brigade of Tennessee infantry from Cleveland , Tennessee , by train to Chickamauga Station . He recalled all units he had recently ordered to Knoxville if they were within a day ' s march . Maj . Gen . Patrick R . Cleburne ' s division returned after dark from Chickamauga Station , interrupting the process of boarding the trains . Bragg began to reduce the strength on his left by withdrawing Maj . Gen . William H . T . Walker ' s division from the base of Lookout Mountain and placing them on the far right of Missionary Ridge , just south of Tunnel Hill . He assigned Lt . Gen . William J . Hardee to command his now critical right flank , turning over the left flank to Maj . Gen . Carter L . Stevenson . Bragg ' s concern for his right proved justified and his decisions were fortuitous . In the center , Maj . Gen . John C . Breckinridge ordered his men to begin fortifying the crest of Missionary Ridge , a task that Bragg had somehow neglected for weeks . Unable to decide whether to defend the base or the crest of the Ridge , the divisions of Brig . Gens . William B . Bate and J . Patton Anderson were ordered to move half of their divisions to the crest , leaving the remainder in the rifle pits along the base . James L . McDonough wrote of the upper entrenchments , " Placed along the physical crest rather than what is termed the military crest . . . these works severely handicapped the defenders . " November 24 was dark , with low clouds , fog , and drizzling rain . Sherman ' s force crossed the Tennessee River successfully in the morning then took the set of hills at the north end of Missionary Ridge , although he was surprised to find that a valley separated him from the main part of the ridge . Alerted by Grigsby ' s cavalry that the enemy had crossed the river in force , Bragg sent Cleburne ' s division and Wright ' s brigade to challenge Sherman . After skirmishing with the Confederates , Sherman ordered his men to dig in on the hills he had seized . Cleburne , likewise , dug in around Tunnel Hill . At the same time , Hooker ' s command succeeded in the Battle of Lookout Mountain and prepared to move east toward Bragg ' s left flank on Missionary Ridge . The divisions of Stevenson and Cheatham retreated behind Chattanooga Creek , burning the bridges behind them . On the night of November 24 , Bragg asked his two corps commanders whether to retreat or to stand and fight . Cleburne , concerned about what Sherman had accomplished , expected Bragg to retreat . Hardee also counseled retreat , but Breckinridge convinced Bragg to fight it out on the strong position of Missionary Ridge . Accordingly , the troops withdrawn from Lookout Mountain were ordered to the right wing to assist in repelling Sherman . Opposing forces . Grant ' s Military Division of the Mississippi assembled the following forces at Chattanooga : Bragg ' s Army of Tennessee had the following forces available in Chattanooga : On November 5 , Bragg had seriously weakened his forces by sending Longstreet ' s Corps , commanded by Lt . Gen . James Longstreet , with the divisions of Maj . Gen . Lafayette McLaws and Brig . Gen . Micah Jenkins ( Hood ' s Division ) , against Maj . Gen . Ambrose Burnside near Knoxville . On November 22 , Bragg had further weakened his forces by ordering the division of Maj . Gen . Simon B . Buckner to reinforce Longstreet at Knoxville . Battle . On November 25 , Grant ' s plan concentrated on the attack by Sherman against Bragg ' s right flank at Tunnel Hill . He gave a supporting role to Thomas : Grant had no particular expectation for Hooker other than to divert Bragg ' s attention by continued demonstrations on Lookout Mountain . However , Thomas wanted support on his flank and called Hooker to cross the valley and demonstrate against Bragg ' s left flank directly at the Rossville Gap . Sherman at Tunnel Hill . In a letter to his brother , Sherman wrote : Sherman had about 16 , 600 men in the three divisions of Brig . Gens . Morgan L . Smith , John E . Smith , and his foster brother and brother - in - law Hugh Ewing , and three regiments of Col . Adolphus Buschbeck ' s brigade from the XI Corps ; Hardee had about 9 , 000 Confederates in the divisions of Cleburne and Walker with another 4 , 000 soon to arrive in Stevenson ' s division . Sherman also had Jefferson C . Davis ' s division guarding his rear ; likewise Hardee had Benjamin F . Cheatham ' s division in reserve . However , at dawn , when Sherman initially planned to attack , he was opposed by three small brigades under Cleburne — about 4 , 000 men — and only the Texas brigade of Brig . Gen . James A . Smith was actually positioned on Tunnel Hill . But seemingly unnerved by his incorrect positioning , Sherman delayed well past his orders to attack at dawn . He selected just two brigades from Ewing ' s division to attack . Brig . Gen . John M . Corse would approach from the north , Col . John M . Loomis from the northwest , across the open fields between the railroads . Sherman ordered Corse ' s brigade , with a detachment from Joseph A . J . Lightburn ' s brigade , to attack along the narrow length of Tunnel Hill . Col . John M . Loomis ' s brigade , supported by Bushbeck , would move across the open fields on the west of the ridge while Brig . Gen . Giles A . Smith ' s brigade would move through the valley on the east side of the ridge . The brigades of Brig . Gen . Charles L . Matthies and Col . Green B . Raum were held in reserve to follow up any successful attack ; the brigades of Cols . Joseph R . Cockerill and Jesse I . Alexander would hold the heights seized the day before . Corse drove off the Confederate skirmish line and seized some half - built defensive works at the north end of Tunnel Hill . Continuing over the crest of the hill , Corse charged Cleburne ' s main position but was repulsed . After several attempts , Sherman gave up on attacking from Corse ' s position and the fighting shifted to the west side of the ridge . Loomis had advanced to the railroad in front of the ridge where he skirmished with Walker ' s division . Bushbeck , followed by Matthies and then Raum were sent up the west slope of Tunnel Hill between Loomis and Corse . Cleburne ' s salient began to feel the pressure and it came close to breaking . Hardee fed in reinforcements from Stevenson ' s division , and Cleburne ordered a general counterattack . Charging down the hill at 4 p . m . , the Confederates routed Sherman ' s men , who were too tired and low on ammunition to resist , and captured numerous Federal prisoners . Sherman ' s attack came to a halt , a tactical failure in which he lost almost 2 , 000 casualties but committed only a fraction of his available force in a direct assault on a strong position , rather than attempting to outflank Bragg . Military historian David Eicher called this Sherman ' s " worst experience as a commander , first miscalculating the terrain and then stumbling through a prolonged , unsuccessful , and needless attack . " On the other hand , Steven E . Woodworth judged that " Cleburne was in fine form today , deftly shifting troops around his hilltop position and skillfully judging when and where to launch limited counterattacks — often leading them himself . " An alternative view has been expressed by B . H . Liddell Hart , who contends that Sherman did not commit his entire force because he was expecting Bragg to attack him to dislodge the Union force from a threatening position . He " gave the Confederates several hours in which to attack them and when he saw that they showed no signs of accepting the invitation , he made it more pressing by launching three brigades against their position . But his real desire is unmistakably established by the fact that he kept three brigades to hold his own ridge , with five more in reserve behind . " Thomas ' s assault on the Confederate center . At around 2 : 30 p . m . , Grant spoke with Brig . Gen . Thomas J . Wood , a classmate of his from West Point . " General Sherman seems to be having a hard time , " Grant observed . " It seems as if we ought to go help him . " He decided to send Wood ' s and Maj . Gen . Philip H . Sheridan ' s divisions against the Confederate rifle pits at the base of the ridge , hoping to concern Bragg and relieve the pressure on Sherman . Grant suggested his idea to Thomas , but personal relations between the two generals were chilly during the campaign and Thomas rebuffed Grant ' s idea — he had no intention of attacking until he was assured that Hooker was successfully attacking the enemy ' s flank . Meanwhile , IV Corps commander Maj . Gen . Gordon Granger was nearby , completely absorbed in the activities of a battery of artillery . Irritated , Grant asked Thomas to order Granger to " take command of his own corps . And now order your troops to advance and take the enemy ' s first line of rifle pits . " At 3 p . m . Thomas passed the order to Granger , but incredibly , Granger ignored the order and resumed commanding the battery of artillery . After a further scolding from Grant , Granger finally issued orders to Wood and Sheridan . Messengers also went to Brig . Gens . Absalom Baird and Richard W . Johnson of Maj . Gen . John M . Palmer ' s XIV Corps , ordering them to move upon hearing the rapid , successive discharge of six artillery pieces . Thomas deployed 23 , 000 men in four divisions with brigades in line — from left to right ( north to south ) , the divisions of Baird ( brigades of Col . Edward H . Phelps , Col . Ferdinand Van Derveer , and Brig . Gen . John B . Turchin ) , Wood ( brigades of Brig . Gens . Samuel Beatty , August Willich , and William B . Hazen ) , Sheridan ( brigades of Brig . Gen . George D . Wagner , Col . Charles G . Harker , and Col . Francis T . Sherman ) , and Johnson ( brigades of Col . William L . Stoughton and Brig . Gen . William P . Carlin ) . Each brigade consisted of two lines , one behind the other , with skirmishers leading the way . There were about 14 , 000 Confederates defending the center of the ridge against which Thomas ' s men marched , overlapping just slightly the Union approach . From right to left ( north to south ) were Cheatham ' s division ( brigades of Brig . Gens . Edward C . Walthall , John C . Moore , and John K . Jackson ) , Hindman ' s division ( commanded by Brig . Gen . J . Patton Anderson , brigades of Brig . Gens . Alfred J . Vaughan , Zachariah C . Deas , and Arthur M . Manigault ) , Breckinridge ' s division ( commanded by Brig . Gen . William B . Bate , brigades of Brig . Gen . Joseph H . Lewis , Col . R . C . Tyler , and Brig . Gen . Jesse J . Finley ) , and Stewart ' s division ( brigades of Col . Randall L . Gibson , Brig . Gen . Otho F . Strahl , Brig . Gen . Marcellus A . Stovall , and Col . James T . Holtzclaw ) . At about 3 : 40 p . m . , the signal guns fired before Baird could brief Turchin . Some regimental officers claimed to get conflicting orders from the same brigadier . When asked where he was to stop , Willich told one officer , " I don ' t know , at Hell , I expect . " Sheridan sent an orderly back to Granger inquiring whether the objective was the base or the top of the ridge , but the signal guns fired before he got an answer . Wagner , Turchin , and Carlin thought they were supposed to carry the ridge top . Most officers were guided only by what the units on either side of them did . The 9 , 000 Confederates holding the rifle pits at the base of the ridge were also plagued by conflicting orders . Some were ordered to fire a volley then retreat , others to hold their ground . Those who stayed to fight were swamped by Union numbers . The Union tide was irresistible , with charging men shouting , " Chickamauga ! Chickamauga ! " Many of the Confederates were captured while the rest started the 5 – 600 - foot climb to the ridge top in fear of being shot in the back . Those who escaped were completely winded by the effort and in no shape to defend themselves for several minutes . The 100 Confederate cannons initially hit few of their enemies during the Union rush , but once the Union soldiers stopped at the rifle pits , they began to zero in on them . The Confederate riflemen also poured in their fire . Some Union unit commanders moved their men forward to get out of the worst fire . Willich ' s skirmishers started up the ridge without orders . Deciding that following them was preferable to being massacred in the rifle pits , Willich gave orders to advance , although several of his units were already doing so . Seeing this , Hazen and Beatty also ordered their first lines up . When Wood reached the rifle pits , the men in the second line begged him to order them up as well . Wood sent them forward . Grant was shocked when he saw the Union troops climbing the ridge . He asked first Thomas then Granger who had given the orders . Neither general claimed responsibility , but Granger replied , " When those fellows get started all hell can ' t stop them . " Granger then sent a courier to Wood allowing him permission to take the ridge top , if he thought it possible . Several messengers went out at about this time with differing orders , leading to more confusion . On the far left Phelps and Van Derveer captured the rifle pits and held their position . Having negotiated some rough ground , Turchin ' s brigade lagged behind . But as soon as his men overran the rifle pits , the " Mad Russian " immediately urged his men up the ridge . Before Baird could send his other two brigades , he received an order to halt . Wagner ' s and Harker ' s men started climbing soon after Wood ' s brigades . Wagner got halfway up before he received an order that he was to stop at the base of the ridge . He ordered his men to pull back . As they did , they suffered heavy losses from the elated Confederate defenders . Wagner ' s brigade suffered more casualties , around 22 % , than any other brigade in the assault . When Wagner and some of Harker ' s men returned to the rifle pits they saw that Wood ' s division on their left and units of their own division on the right were still moving uphill . Disgusted that a rival division was getting ahead , Wagner sent his second line up the ridge . Sheridan soon ordered Harker back up also . To their right , Francis Sherman ' s brigade faced an entrenched line about one - half of the way up the ridge and had hard going . On the far right , Johnson ' s two brigades faced determined resistance at the rifle pits and were slow in starting up the ridge . The Confederate line first cracked at Bird ' s Mill Road , at about 5 p . m . One of Willich ' s regiments , joined by two of Hazen ' s , worked its way within 50 yards of the Confederate breastworks . Protected by a roll of ground , they crept closer , then with a rush they leaped over the works belonging to Col . William F . Tucker ' s brigade . Surprised , the nearest defenders surrendered or fled for their lives . Alertly , the Union field officers swung their regiments to the right and left and began rolling up the Confederate line . Tucker bravely rallied his men , but by this time Willich and Hazen ' s men were flooding over the breastworks . Since Bragg had not provided for a tactical reserve , his defenses were only a thin crust . To seal off the breach , the Southern generals were placed on the horns of a dilemma . When they found Union troops on their flank , they had to pull regiments out of their defense line for a counterattack . This weakened the main line of resistance just as the Union brigades to their front were swarming up to the crest . Once atop the ridge , Hazen swung his brigade south . The Confederate lines in this direction were held by Brig . Gen . Alexander W . Reynolds ' s brigade , whose men had to endure a hard climb from the base of the ridge . Hit in front and flank , most of Reynolds ' s tired men melted away . Continuing south , Hazen flanked Col . R . C . Tyler ' s brigade of Bate ' s division out of position , allowing Wagner ' s brigade to reach the crest . Bate ' s Florida brigade was soon driven away , allowing Harker ' s men to reach the top . Col . Randall L . Gibson ' s brigade was defeated by Francis Sherman ' s men . Dogged by tough resistance and very steep slopes , Johnson ' s two brigades took the longest to climb the ridge , Carlin ' s men finally reaching the top around 5 : 30 p . m . Seeing that his position was hopeless , Stewart pulled the brigades of Brig . Gens . Otho F . Strahl and Marcellus A . Stovall off the ridge . Meanwhile , Willich wheeled to the north and began crushing the flank of Anderson ' s division . Willich ' s success assisted Beatty ' s brigade to get to the top . The two brigades first drove off Brig . Gen . Arthur M . Manigault ' s men and continued rolling north . As they came up the ridge , the Union brigades of Turchin , Van Derveer , and Phelps ( who was killed near the crest ) added their weight to the assault against the Confederate brigades of Brig . Gens . Zachariah C . Deas , Alfred J . Vaughan , and John K . Jackson . Some Confederate soldiers resisted stubbornly , but many panicked and ran when they realized that Union troops were bearing down on them from the flank . Often , the Southern infantry fled before the supporting artillerists could escape with their cannons . In this manner , Anderson ' s entire division and Cheatham ' s left flank brigades of Brig . Gens . Jackson and Moore were routed . The northward Federal advance was only stopped by the stout fighting of Walthall ' s brigade and nightfall . Cheatham , Gist , Stevenson , and Cleburne were able to get their divisions away more or less intact , although the Confederate soldiers were demoralized or chagrined by their defeat . The Army of the Cumberland ' s ascent of Missionary Ridge was one of the war ' s most dramatic events . Military historians Herman Hattaway and Archer Jones contend that the Battle of Missionary Ridge was " the war ' s most notable example of a frontal assault succeeding against entrenched defenders holding high ground . " A Union officer remembered that By 6 p . m . , the center of Bragg ' s line had broken completely and fled in panic , requiring the abandonment of Missionary Ridge and a headlong retreat eastward to South Chickamauga Creek . The sole exception to the panicked flight was Cleburne ' s command , his division augmented by two brigades from another division . As the only command not in complete disarray , it was the last unit to withdraw and formed the rearguard of Bragg ' s army as it retreated eastward . Only Sheridan tried to pursue beyond Missionary Ridge , but he finally gave up late that night when it was clear that he was not being supported by either Granger or Thomas . Hooker at Rossville Gap . After Maj . Gen . Joseph Hooker ' s command left Lookout Mountain at about 10 a . m . and moved east , they encountered a significant obstacle . The bridge across Chattanooga Creek , about a mile from Rossville Gap , had been burned by the Confederates as they withdrew the night before and the creek was running high . Brig . Gen . Peter J . Osterhaus assigned a 70 - man pioneer unit to start rebuilding the bridge while men of the 27th Missouri created a rickety footbridge and began crossing one by one . Hooker decided to leave his guns and wagons behind so that all of his infantry could cross first , but his advance was delayed about three hours and he did not reach Rossville Gap until 3 : 30 p . m . Breckinridge was absent while the Union attack wrecked his corps . Worried about his left flank , he rode to the end of his line in the early afternoon . At 3 : 30 p . m . , about the time Thomas launched his four - division attack on Missionary Ridge , Breckinridge visited Stewart ' s left flank brigade of Col . James T . Holtzclaw , whose commander pointed to the southwest where Hooker ' s men were busily bridging Chattanooga Creek . Concerned about Rossville Gap , which lay undefended beyond his left flank , Breckinridge ordered Holtzclaw to send a couple of regiments to hold the position . It was too late ; by the time the Southerners reached the gap , Osterhaus ' s division had already marched through . Lt . J . Cabell Breckinridge , the general ' s son and aide - de - camp , rode into a group from the 9th Iowa and was captured . Hooker quickly faced his troops to the north and organized a three - pronged attack . He sent Osterhaus along a trail east of Missionary Ridge , Cruft onto the ridge itself , and Geary along the western face of the ridge . Holtzclaw faced his men south and put up a fight , but Cruft and Osterhaus soon began herding the outnumbered Confederates north along Missionary Ridge . Hearing a tremendous racket to the north , Breckinridge finally rode off to find out what was wrong . As Holtzclaw retreated before Hooker ' s command , he eventually bumped into Col . Anson G . McCook ' s 2nd Ohio of Carlin ' s brigade , now astride the ridge . Surrounded by superior forces on four sides , approximately 700 of Holtzclaw ' s men surrendered . Aftermath . During the night , Bragg ordered his army to withdraw toward Chickamauga Station on the Western & Atlantic Railroad ( currently the site of Lovell Air Field ) and the following day began retreating from there toward Dalton , Georgia , in two columns over two routes . The pursuit ordered by Grant was effectively thwarted by Cleburne ' s defense at the Battle of Ringgold Gap . Casualties for the Union Army during the Battles for Chattanooga ( Orchard Knob , Lookout Mountain , and Missionary Ridge ) amounted to 5 , 824 ( 753 killed , 4 , 722 wounded , and 349 missing ) of about 56 , 000 engaged ; Confederate casualties were 6 , 667 ( 361 killed , 2 , 160 wounded , and 4 , 146 missing , mostly prisoners ) of about 44 , 000 . Southern losses may have been higher ; Grant claimed 6 , 142 prisoners . In addition , the Union Army seized 40 cannons and 69 limbers and caissons . When a chaplain asked General Thomas whether the dead should be sorted and buried by state , Thomas replied " Mix ' em up . I ' m tired of states ' rights . " The Confederate enthusiasm that had risen so high after Chickamauga had been dashed at Chattanooga . One of the Confederacy ' s two major armies was routed . The Union now held undisputed control of the state of Tennessee , including Chattanooga , the " Gateway to the Lower South . " The city became the supply and logistics base for Sherman ' s 1864 Atlanta Campaign , as well as for the Army of the Cumberland , and Grant had won his final battle in the West prior to receiving command of all Union armies in March 1864 .