Battle of Gettysburg , First Day The First Day of the Battle of Gettysburg during the American Civil War took place on July 1 , 1863 , and began as an engagement between isolated units of the Army of Northern Virginia under Confederate General Robert E . Lee and the Army of the Potomac under Union Maj . Gen . George G . Meade . It soon escalated into a major battle which culminated in the outnumbered and defeated Union forces retreating to the high ground south of Gettysburg , Pennsylvania . The first - day battle proceeded in three phases as combatants continued to arrive at the battlefield . In the morning , two brigades of Confederate Maj . Gen . Henry Heth ' s division ( of Lt . Gen . A . P . Hill ' s Third Corps ) were delayed by dismounted Union cavalrymen under Brig . Gen . John Buford . As infantry reinforcements arrived under Maj . Gen . John F . Reynolds of the Union I Corps , the Confederate assaults down the Chambersburg Pike were repulsed , although Gen . Reynolds was killed . By early afternoon , the Union XI Corps had arrived , and the Union position was in a semicircle from west to north of the town . The Confederate Second Corps under Lt . Gen . Richard S . Ewell began a massive assault from the north , with Maj . Gen . Robert E . Rodes ' s division attacking from Oak Hill and Maj . Gen . Jubal A . Early ' s division attacking across the open fields north of town . The Union lines generally held under extremely heavy pressure , although the salient at Barlow ' s Knoll was overrun . The third phase of the battle came as Rodes renewed his assault from the north and Heth returned with his entire division from the west , accompanied by the division of Maj . Gen . W . Dorsey Pender . Heavy fighting in Herbst ' s Woods ( near the Lutheran Theological Seminary ) and on Oak Ridge finally caused the Union line to collapse . Some of the Federals conducted a fighting withdrawal through the town , suffering heavy casualties and losing many prisoners ; others simply retreated . They took up good defensive positions on Cemetery Hill and waited for additional attacks . Despite discretionary orders from Robert E . Lee to take the heights " if practicable , " Richard Ewell chose not to attack . Historians have debated ever since how the battle might have ended differently if he had found it practicable to do so . Morning . Defense by Buford ' s cavalry . On the morning of July 1 , Union cavalry in the division of Brig . Gen . John Buford were awaiting the approach of Confederate infantry forces from the direction of Cashtown , to the northwest . Confederate forces from the brigade of Brig . Gen . J . Johnston Pettigrew had briefly clashed with Union forces the day before but believed they were Pennsylvania militia of little consequence , not the regular army cavalry that was screening the approach of the Army of the Potomac . General Buford realized the importance of the high ground directly to the south of Gettysburg . He knew that if the Confederates could gain control of the heights , Meade ' s army would have a hard time dislodging them . He decided to utilize three ridges west of Gettysburg : Herr Ridge , McPherson Ridge , and Seminary Ridge ( proceeding west to east toward the town ) . These were appropriate terrain for a delaying action by his small division against superior Confederate infantry forces , meant to buy time awaiting the arrival of Union infantrymen who could occupy the strong defensive positions south of town , Cemetery Hill , Cemetery Ridge , and Culp ' s Hill . Early that morning , Reynolds , who was commanding the Left Wing of the Army of the Potomac , ordered his corps to march to Buford ' s location , with the XI Corps ( Maj . Gen . Oliver O . Howard ) to follow closely behind . Confederate Maj . Gen . Henry Heth ' s division , from Lt . Gen . A . P . Hill ' s Third Corps , advanced towards Gettysburg . Heth deployed no cavalry and led , unconventionally , with the artillery battalion of Major William J . Pegram . Two infantry brigades followed , commanded by Brig . Gens . James J . Archer and Joseph R . Davis , proceeding easterly in columns along the Chambersburg Pike . Three miles ( 5 km ) west of town , about 7 : 30 a . m . , Heth ' s two brigades met light resistance from cavalry vedette s and deployed into line . Eventually , they reached dismounted troopers from Col . William Gamble ' s cavalry brigade . The first shot of the battle was claimed to be fired by Lieutenant Marcellus E . Jones of the 8th Illinois Cavalry , fired at an unidentified man on a gray horse over a half - mile away ; the act was merely symbolic . Buford ' s 2 , 748 troopers would soon be faced with 7 , 600 Confederate infantrymen , deploying from columns into line of battle . Gamble ' s men mounted determined resistance and delaying tactics from behind fence posts with rapid fire from their breech - loading carbine s . It is a modern myth that they were armed with multi - shot repeating carbines . Nevertheless , they were able to fire two or three times faster than a muzzle - loaded carbine or rifle . Also , the breech - loading design meant that Union troops did not have to stand to reload and could do so safely behind cover . This was a great advantage over the Confederates , who still had to stand to reload , thus providing an easier target . But this was so far a relatively bloodless affair . By 10 : 20 a . m . , the Confederates had reached Herr Ridge and had pushed the Federal cavalrymen east to McPherson Ridge , when the vanguard of the I Corps finally arrived , the division of Maj . Gen . James S . Wadsworth . The troops were led personally by Gen . Reynolds , who conferred briefly with Buford and hurried back to bring more men forward . Davis versus Cutler . The morning infantry fighting occurred on either side of the Chambersburg Pike , mostly on McPherson Ridge . To the north , an unfinished railroad bed opened three shallow cuts in the ridges . To the south , the dominant features were Willoughby Run and Herbst Woods ( sometimes called McPherson Woods , but they were the property of John Herbst ) . Brig . Gen . Lysander Cutler ' s Union brigade opposed Davis ' s brigade ; two of Cutler ' s regiments were north of the Pike , two to the south . To the left of Cutler , Brig . Gen . Solomon Meredith ' s Iron Brigade opposed Archer . General Reynolds directed both brigades into position and placed guns from the Maine battery of Capt . James A . Hall where Calef ' s had stood earlier . While the general rode his horse along the east end of Herbst Woods , shouting " Forward men ! Forward for God ' s sake , and drive those fellows out of the woods , " he fell from his horse , killed instantly by a bullet striking him behind the ear . ( Some historians believe Reynolds was felled by a sharpshooter , but it is more likely that he was killed by random shot in a volley of rifle fire directed at the 2nd Wisconsin . ) Maj . Gen . Abner Doubleday assumed command of the I Corps . On the right of the Union line , three regiments of Cutler ' s brigade were fired on by Davis ' s brigade before they could get into position on the ridge . Davis ' s line overlapped the right of Cutler ' s , making the Union position untenable , and Wadsworth ordered Cutler ' s regiments back to Seminary Ridge . The commander of the 147th New York , Lt . Col . Francis C . Miller , was shot before he could inform his troops of the withdrawal , and they remained to fight under heavy pressure until a second order came . In under 30 minutes , 45 % of Gen . Cutler ' s 1 , 007 men became casualties , with the 147th losing 207 of its 380 officers and men . Some of Davis ' s victorious men turned toward the Union positions south of the railroad bed while others drove east toward Seminary Ridge . This defocused the Confederate effort north of the pike . Archer versus Meredith . South of the pike , Archer ' s men were expecting an easy fight against dismounted cavalrymen and were astonished to recognize the black Hardee hat s worn by the men facing them through the woods : the famous Iron Brigade , formed from regiments in the Western states of Indiana , Michigan , and Wisconsin , had a reputation as fierce , tenacious fighters . As the Confederates crossed Willoughby Run and climbed the slope into Herbst Woods , they were enveloped on their right by the longer Union line , the reverse of the situation north of the pike . Brig . Gen . Archer was captured in the fighting , the first general officer in Robert E . Lee ' s army to suffer that fate . Archer was most likely positioned around the 14th Tennessee when he was captured by Private Patrick Moloney of Company G . , 2nd Wisconsin , " a brave patriotic and fervent young Irishman . " Archer resisted capture , but Moloney overpowered him . Moloney was killed later that day , but he received the Medal of Honor for his exploit . When Archer was taken to the rear , he encountered his former Army colleague Gen . Doubleday , who greeted him good - naturedly , " Good morning , Archer ! How are you ? I am glad to see you ! " Archer replied , " Well , I am " not " glad to see " you " by a damn sight ! " Railroad cut . At around 11 a . m . , Doubleday sent his reserve regiment , the 6th Wisconsin , an Iron Brigade regiment , commanded by Lt . Col . Rufus R . Dawes , north in the direction of Davis ' s disorganized brigade . The Wisconsin men paused at the fence along the pike and fired , which halted Davis ' s attack on Cutler ' s men and caused many of them to seek cover in the unfinished railroad cut . The 6th joined the 95th New York and the 84th New York ( also known as the 14th Brooklyn ) , a " demi - brigade " commanded by Col . E . B . Fowler , along the pike . The three regiments charged to the railroad cut , where Davis ' s men were seeking cover . The majority of the 600 - foot ( 180 m ) cut ( shown on the map as the center cut of three ) was too deep to be an effective firing position — as deep as 15 feet ( 4 . 5 m ) . Making the situation more difficult was the absence of their overall commander , General Davis , whose location was unknown . The men of the three regiments nevertheless faced daunting fire as they charged toward the cut . The 6th Wisconsin ' s American flag went down at least three times during the charge . At one point Dawes took up the fallen flag before it was seized from him by a corporal of the color guard . As the Union line neared the Confederates , its flanks became folded back and it took on the appearance of an inverted V . When the Union men reached the railroad cut , vicious hand - to - hand and bayonet fighting broke out . They were able to pour enfilading fire from both ends of the cut , and many Confederates considered surrender . Colonel Dawes took the initiative by shouting " Where is the colonel of this regiment ? " Major John Blair of the 2nd Mississippi stood up and responded , " Who are you ? " Dawes replied , " I command this regiment . Surrender or I will fire . " Dawes later described what happened next : Despite this surrender , leaving Dawes standing awkwardly holding seven swords , the fighting continued for minutes more and numerous Confederates were able to escape back to Herr Ridge . The three Union regiments lost 390 – 440 of 1 , 184 engaged , but they had blunted Davis ' s attack , prevented them from striking the rear of the Iron Brigade , and so overwhelmed the Confederate brigade that it was unable to participate significantly in combat for the rest of the day . The Confederate losses were about 500 killed and wounded and over 200 prisoners out of 1 , 707 engaged . Midday lull . By 11 : 30 a . m . , the battlefield was temporarily quiet . On the Confederate side , Henry Heth faced an embarrassing situation . He had been under orders from General Lee to avoid a general engagement until the full Army of Northern Virginia had concentrated in the area . But his excursion to Gettysburg , ostensibly to find shoes , was essentially a reconnaissance in force conducted by a full infantry division . This indeed had started a general engagement and Heth was on the losing side so far . By 12 : 30 p . m . , his remaining two brigades , under Brig . Gen . J . Johnston Pettigrew and Col . John M . Brockenbrough , had arrived on the scene , as had the division ( four brigades ) of Maj . Gen . Dorsey Pender , also from Hill ' s Corps . Hill ' s remaining division ( Maj . Gen . Richard H . Anderson ) did not arrive until late in the day . Considerably more Confederate forces were on the way , however . Two divisions of the Second Corps , commanded by Lt . Gen . Richard S . Ewell , were approaching Gettysburg from the north , from the towns of Carlisle and York . The five brigades of Maj . Gen . Robert E . Rodes marched down the Carlisle Road but left it before reaching town to advance down the wooded crest of Oak Ridge , where they could link up with the left flank of Hill ' s Corps . The four brigades under Maj . Gen . Jubal A . Early approached on the Harrisburg Road . Union cavalry outposts north of the town detected both movements . Ewell ' s remaining division ( Maj . Gen . Edward " Allegheny " Johnson ) did not arrive until late in the day . On the Union side , Doubleday reorganized his lines as more units of the I Corps arrived . First on hand was the Corps Artillery under Col . Charles S . Wainwright , followed by two brigades from Doubleday ' s division , now commanded by Brig . Gen . Thomas A . Rowley , which Doubleday placed on either end of his line . The XI Corps arrived from the south before noon , moving up the Taneytown and Emmitsburg Roads . Maj . Gen . Oliver O . Howard was surveying the area from the roof of the Fahnestock Brothers ' dry - goods store downtown at about 11 : 30 when he heard that Reynolds had been killed and that he was now in command of all Union forces on the field . He recalled : " My heart was heavy and the situation was grave indeed , but surely I did not hesitate a moment . God helping us , we will stay here till the Army comes . I assumed the command of the field . " Howard immediately sent messengers to summon reinforcements from the III Corps ( Maj . Gen . Daniel E . Sickles ) and the XII Corps ( Maj . Gen . Henry W . Slocum ) . Howard ' s first XI Corps division to arrive , under Maj . Gen . Carl Schurz , was sent north to take a position on Oak Ridge and link up with the right of the I Corps . ( The division was commanded temporarily by Brig . Gen . Alexander Schimmelfennig while Schurz filled in for Howard as XI Corps commander . ) The division of Brig . Gen . Francis C . Barlow was placed on Schurz ' s right to support him . The third division to arrive , under Brig . Gen . Adolph von Steinwehr , was placed on Cemetery Hill along with two batteries of artillery to hold the hill as a rallying point if the Union troops could not hold their positions ; this placement on the hill corresponded with orders sent earlier in the day to Howard by Reynolds just before he was killed . However , Rodes beat Schurz to Oak Hill , so the XI Corps division was forced to take up positions in the broad plain north of the town , below and to the east of Oak Hill . They linked up with the I Corps reserve division of Brig . Gen . John C . Robinson , whose two brigades had been sent forward by Doubleday when he heard about Ewell ' s arrival . Howard ' s defensive line was not a particularly strong one in the north . He was soon outnumbered ( his XI Corps , still suffering the effects of their defeat at the Battle of Chancellorsville , had only 8 , 700 effectives ) , and the terrain his men occupied in the north was poorly selected for defense . He held out some hope that reinforcements from Slocum ' s XII Corps would arrive up the Baltimore Pike in time to make a difference . Afternoon . In the afternoon , there was fighting both west ( Hill ' s Corps renewing their attacks on the I Corps ) and north ( Ewell ' s Corps attacking the I and XI Corps ) of Gettysburg . Ewell , on Oak Hill with Rodes , saw Howard ' s troops deploying before him , and he interpreted this as the start of an attack and implicit permission to set aside Gen . Lee ' s order not to bring about a general engagement . Rodes attacks from Oak Hill . Rodes initially sent three brigades south against Union troops that represented the right flank of the I Corps and the left flank of the XI Corps : from east to west , Brig . Gen . George P . Doles , Col . Edward A . O ' Neal , and Brig . Gen . Alfred Iverson . Doles ' s Georgia brigade stood guarding the flank , awaiting the arrival of Early ' s division . Both O ' Neal ' s and Iverson ' s attacks fared poorly against the six veteran regiments in the brigade of Brig . Gen . Henry Baxter , manning a line in a shallow inverted V , facing north on the ridge behind the Mummasburg Road . O ' Neal ' s men were sent forward without coordinating with Iverson on their flank and fell back under heavy fire from the I Corps troops . Iverson failed to perform even a rudimentary reconnaissance and sent his men forward blindly while he stayed in the rear ( as had O ' Neal , minutes earlier ) . More of Baxter ' s men were concealed in woods behind a stone wall and rose to fire withering volleys from less than away , creating over 800 casualties among the 1 , 350 North Carolinians . Stories are told about groups of dead bodies lying in almost parade - ground formations , heels of their boots perfectly aligned . ( The bodies were later buried on the scene , and this area is today known as " Iverson ' s Pits " , source of many local tales of supernatural phenomena . ) Baxter ' s brigade was worn down and out of ammunition . At 3 : 00 p . m . he withdrew his brigade , and Gen . Robinson replaced it with the brigade of Brig . Gen . Gabriel R . Paul . Rodes then committed his two reserve brigades : Brig . Gens . Junius Daniel and Dodson Ramseur . Ramseur attacked first , but Paul ' s brigade held its crucial position . Paul had a bullet go in one temple and out the other , blinding him permanently ( he survived the wound and lived 20 more years after the battle ) . Before the end of the day , three other commanders of that brigade were wounded . Daniel ' s North Carolina brigade then attempted to break the I Corps line to the southwest along the Chambersburg Pike . They ran into stiff resistance from Col . Roy Stone ' s Pennsylvania " Bucktail Brigade " in the same area around the railroad cut as the morning ' s battle . Fierce fighting eventually ground to a standstill . Heth renews his attack . Gen . Lee arrived on the battlefield at about 2 : 30 p . m . , as Rodes ' s men were in mid - attack . Seeing that a major assault was underway , he lifted his restriction on a general engagement and gave permission to Hill to resume his attacks from the morning . First in line was Heth ' s division again , with two fresh brigades : Pettigrew ' s North Carolinians and Col . John M . Brockenbrough ' s Virginians . Pettigrew ' s Brigade was deployed in a line that extended south beyond the ground defended by the Iron Brigade . Enveloping the left flank of the 19th Indiana , Pettigrew ' s North Carolinians , the largest brigade in the army , drove back the Iron Brigade in some of the fiercest fighting of the war . The Iron Brigade was pushed out of the woods , made three temporary stands in the open ground to the east , but then had to fall back toward the Lutheran Theological Seminary . Gen . Meredith was downed with a head wound , made all the worse when his horse fell on him . To the left of the Iron Brigade was the brigade of Col . Chapman Biddle , defending open ground on McPherson Ridge , but they were outflanked and decimated . To the right , Stone ' s Bucktails , facing both west and north along the Chambersburg Pike , were attacked by both Brockenbrough and Daniel . Casualties were severe that afternoon . The 26th North Carolina ( the largest regiment of the army with 839 men ) lost heavily , leaving the first day ' s fight with around 212 men . Their commander , Colonel Henry K . Burgwyn , was fatally wounded by a bullet through his chest . By the end of the three - day battle , they had about 152 men standing , the highest casualty percentage for one battle of any other regiment , North or South . One of the Union regiments , the 24th Michigan , lost 399 of 496 . It had nine color bearers shot down , and its commander , Col . Henry A . Morrow , was wounded in the head and captured . The 151st Pennsylvania of Biddle ' s brigade lost 337 of 467 . The highest ranking casualty of this engagement was Gen . Heth , who was struck by a bullet in the head . He was apparently saved because he had stuffed wads of paper into a new hat , which was otherwise too large for his head . But there were two consequences to this glancing blow . Heth was unconscious for over 24 hours and had no further command involvement in the three - day battle . He was also unable to urge Pender ' s division to move forward and supplement his struggling assault . Pender was oddly passive during this phase of the battle ; the typically more aggressive tendencies of a young general in Lee ' s army would have seen him move forward on his own accord . Hill shared the blame for failing to order him forward as well , but he claimed illness . History cannot know Pender ' s motivations ; he was mortally wounded the next day and left no report . Early attacks XI Corps . Maj . Gen . Oliver O . Howard of the XI Corps had a difficult defensive problem . He had only two divisions ( four brigades ) to cover the wide expanse of featureless farmland north of town . He and Maj . Gen . Carl Schurz , temporarily in command of the corps while Howard was in overall command on the field , deployed the division of Brig . Gen . Alexander Schimmelfennig on the left and Brig . Gen . Francis C . Barlow on the right . From the left , the brigades were Schimmelfennig ' s ( under Col . George von Amsberg ) , Col . Włodzimierz Krzyżanowski , Brig . Gen . Adelbert Ames , and Col . Leopold von Gilsa . Howard recalled that he selected this line as a logical continuation of the I Corps line formed on his left . This decision has been criticized by historians , such as Edwin B . Coddington , as being too far forward , with a right flank vulnerable to envelopment by the enemy . ( Coddington suggests that a more defensible line would have been along Stevens Run , about 600 feet north of the railroad , a shorter line to defend , with better fields of fire , and with a more secure right flank . ) Making the Federal defense more difficult , Barlow advanced farther north than Schimmelfennig ' s division , occupying a 50 - foot ( 15 m ) elevation above Rock Creek named Blocher ' s Knoll ( known today as Barlow ' s Knoll ) . Barlow ' s justification was that he wanted to prevent Doles ' s Brigade , of Rodes ' s division , from occupying it and using it as an artillery platform against him . General Schurz claimed afterward that Barlow had misunderstood his orders by taking this position . ( In Schurz ' s official report , however , he states that Barlow " had been directing the movements of his troops with the most praiseworthy coolness and intrepidity , unmindful of the shower of bullets around , " and " was severely wounded , and had to be carried off the battle - field . " ) By taking the knoll , Barlow was following Howard ' s directive to obstruct the advance of Early ' s division , and in doing so , deprive him of an artillery platform , as von Steinwehr fortified the position on Cemetery Hill . The position on the knoll turned out to be unfortunate , as it created a salient in the line that could be assaulted from multiple sides . Schurz ordered Krzyżanowski ' s brigade , which had heretofore been sitting en masse at the north end of town ( without further order to position from Schurz ) forward to assist Barlow ' s two brigades on the knoll , but they arrived too late and in insufficient numbers to help . Historian Harry W . Pfanz judges Barlow ' s decision to be a " blunder " that " ensured the defeat of the corps . " Richard Ewell ' s second division , under Jubal Early , swept down the Harrisburg Road , deployed in a battle line three brigades wide , almost a mile across ( 1 , 600 m ) and almost half a mile ( 800 m ) wider than the Union defensive line . Early started with a large - scale artillery bombardment . The Georgia brigade of Brigadier - General John B . Gordon was then directed for a frontal attack against Barlow ' s Knoll , pinning down the defenders , while the brigades of Brigadier - General Harry T . Hays and Colonel Isaac E . Avery swung around their exposed flank . At the same time the Georgians under Doles launched a synchronized assault with Gordon . The defenders of Barlow ' s Knoll targeted by Gordon were 900 men of von Gilsa ' s brigade ; in May , two of his regiments had been the initial target of Thomas J . " Stonewall " Jackson ' s flanking attack at Chancellorsville . The men of the 54th and 68th New York held out as long as they could , but they were overwhelmed . Then the 153rd Pennsylvania succumbed . Barlow , attempting to rally his troops , was shot in the side and captured . Barlow ' s second brigade , under Ames , came under attack by Doles and Gordon . Both Union brigades conducted a disorderly retreat to the south . On the left flank of the XI Corps , the attack focused on Gen . Schimmelfennig ' s division . They were subjected to a deadly artillery crossfire from Rodes ' and Early ' s batteries , and as they deployed they were attacked by Doles ' infantry . Early ' s troops were able to employ a flanking attack and roll up the division from the right , and they fell back in confusion toward the town . A desperate counterattack by the 157th New York from von Amsberg ' s brigade was surrounded on three sides , causing it to suffer 307 casualties ( 75 % ) . Gen . Howard , witnessing this disaster , sent forward an artillery battery and an infantry brigade from von Steinwehr ' s reserve force , under Col . Charles Coster . Coster ' s battle line just north of the town in a brickyard was overwhelmed by Hays and Avery . He provided valuable cover for the retreating soldiers , but at a high price : of Coster ' s 800 men , 313 were captured , as were two of the four guns from the battery . The collapse of the XI Corps was completed by 4 p . m . , after a fight of less than an hour . They suffered 3 , 200 casualties ( 1 , 400 of them prisoners ) , about half the number sent forward from Cemetery Hill . The losses in Gordon ' s and Doles ' s brigades were under 750 . Rodes and Pender break through . Rodes ' s original faulty attack at 2 : 00 had stalled , but he launched his reserve brigade , under Ramseur , against Paul ' s Brigade in the salient on the Mummasburg Road , with Doles ' s Brigade against the left flank of the XI Corps . Daniel ' s Brigade resumed its attack , now to the east against Baxter on Oak Ridge . This time Rodes was more successful , mostly because Early coordinated an attack on his flank . In the west , the Union troops had fallen back to the Seminary and built hasty breastworks running north - south before the western face of Schmucker Hall , bolstered by 20 guns of Wainwright ' s battalion . Dorsey Pender ' s division of Hill ' s Corps stepped through the exhausted lines of Heth ' s men at about 4 : 00 p . m . to finish off the I Corps survivors . The brigade of Brig . Gen . Alfred M . Scales attacked first , on the northern flank . His five regiments of 1 , 400 North Carolinians were virtually annihilated in one of the fiercest artillery barrages of the war , rivaling Pickett ' s Charge to come , but on a more concentrated scale . Twenty guns spaced only apart fired spherical case , explosive shells , canister , and double canister rounds into the approaching brigade , which emerged from the fight with only 500 men standing and a single lieutenant in command . Scales wrote afterwards that he found " only a squad here and there marked the place where regiments had rested . " The attack continued in the southern - central area , where Col . Abner M . Perrin ordered his South Carolina brigade ( four regiments of 1 , 500 men ) to advance rapidly without pausing to fire . Perrin was prominently on horseback leading his men but miraculously was untouched . He directed his men to a weak point in the breastworks on the Union left , a gap between Biddle ' s left - hand regiment , the 121st Pennsylvania , and Gamble ' s cavalrymen , attempting to guard the flank . They broke through , enveloping the Union line and rolling it up to the north as Scales ' s men continued to pin down the right flank . By 4 : 30 p . m . , the Union position was untenable , and the men could see the XI Corps retreating from the northern battle , pursued by masses of Confederates . Doubleday ordered a withdrawal east to Cemetery Hill . On the southern flank , the North Carolina brigade of Brig . Gen . James H . Lane contributed little to the assault ; he was kept busy by a clash with Union cavalry on the Hagerstown Road . Brig . Gen . Edward L . Thomas ' s Georgia Brigade was in reserve well to the rear , not summoned by Pender or Hill to assist or exploit the breakthrough . Union retreat . The sequence of retreating units remains unclear . Each of the two corps cast blame on the other . There are three main versions of events extant . The first , most prevalent , version is that the fiasco on Barlow ' s Knoll triggered a collapse that ran counterclockwise around the line . The second is that both Barlow ' s line and the Seminary defense collapsed at about the same time . The third is that Robinson ' s division in the center gave way and that spread both left and right . Gen . Howard told Gen . Meade that his corps was forced to retreat only because the I Corps collapsed first on his flank , which may have reduced his embarrassment but was unappreciated by Doubleday and his men . ( Doubleday ' s career was effectively ruined by Howard ' s story . ) Union troops retreated in different states of order . The brigades on Seminary Ridge were said to move deliberately and slowly , keeping in control , although Col . Wainwright ' s artillery was not informed of the order to retreat and found themselves alone . When Wainwright realized his situation , he ordered his gun crews to withdraw at a walk , not wishing to panic the infantry and start a rout . As pressure eventually increased , Wainwright ordered his 17 remaining guns to gallop down Chambersburg Street , three abreast . A . P . Hill failed to commit any of his reserves to the pursuit of the Seminary defenders , a great missed opportunity . Near the railroad cut , Daniel ' s Brigade renewed their assault , and almost 500 Union soldiers surrendered and were taken prisoner . Paul ' s Brigade , under attack by Ramseur , became seriously isolated and Gen . Robinson ordered it to withdraw . He ordered the 16th Maine to hold its position " at any cost " as a rear guard against the enemy pursuit . The regiment , commanded by Col . Charles Tilden , returned to the stone wall on the Mummasburg Road , and their fierce fire gave sufficient time for the rest of the brigade to escape , which they did , in considerably more disarray than those from the Seminary . The 16th Maine started the day with 298 men , but at the end of this holding action there were only 35 survivors . For the XI Corps , it was a sad reminder of their retreat at Chancellorsville in May . Under heavy pursuit by Hays and Avery , they clogged the streets of the town ; no one in the corps had planned routes for this contingency . Hand - to - hand fighting broke out in various places . Parts of the corps conducted an organized fighting retreat , such as Coster ' s stand in the brickyard . The private citizens of Gettysburg panicked amidst the turmoil , and artillery shells bursting overhead and fleeing refugees added to the congestion . Some soldiers sought to avoid capture by hiding in basements and in fenced backyards . Gen . Alexander Schimmelfennig was one such person who climbed a fence and hid behind a woodpile in the kitchen garden of the Garlach family for the rest of the three - day battle . The only advantage that the XI Corps soldiers had was that they were familiar with the route to Cemetery Hill , having passed through that way in the morning ; many in the I Corps , including senior officers , did not know where the cemetery was . As the Union troops climbed Cemetery Hill , they encountered the determined Maj . Gen . Winfield Scott Hancock . At midday , Gen . Meade was nine miles ( 14 km ) south of Gettysburg in Taneytown , Maryland , when he heard that Reynolds had been killed . He immediately dispatched Hancock , commander of the II Corps and his most trusted subordinate , to the scene with orders to take command of the field and to determine whether Gettysburg was an appropriate place for a major battle . ( Meade ' s original plan had been to man a defensive line on Pipe Creek , a few miles south in Maryland . But the serious battle underway was making that a difficult option . ) When Hancock arrived on Cemetery Hill , he met with Howard and they had a brief disagreement about Meade ' s command order . As the senior officer , Howard yielded only grudgingly to Hancock ' s direction . Although Hancock arrived after 4 : 00 p . m . and commanded no units on the field that day , he took control of the Union troops arriving on the hill and directed them to defensive positions with his " imperious and defiant " ( and profane ) persona . As to the choice of Gettysburg as the battlefield , Hancock told Howard " I think this the strongest position by nature upon which to fight a battle that I ever saw . " When Howard agreed , Hancock concluded the discussion : " Very well , sir , I select this as the battle - field . " Brig . Gen . Gouverneur K . Warren , chief engineer of the Army of the Potomac , inspected the ground and concurred with Hancock . Evening . Gen . Lee also understood the defensive potential to the Union army if they held the high ground of Cemetery Hill . He sent orders to Ewell to " carry the hill occupied by the enemy , if he found it practicable , but to avoid a general engagement until the arrival of the other divisions of the army . " In the face of this discretionary , and possibly contradictory , order , Ewell chose not to attempt the assault . One reason posited was the battle fatigue of his men in the late afternoon , although " Allegheny " Johnson ' s division of Ewell ' s Corps was within an hour of arriving on the battlefield . Another was the difficulty of assaulting the hill through the narrow corridors afforded by the streets of Gettysburg immediately to the north . Ewell requested assistance from A . P . Hill , but that general felt his corps was too depleted from the day ' s battle and General Lee did not want to bring up Maj . Gen . Richard H . Anderson ' s division from the reserve . Ewell did consider taking Culp ' s Hill , which would have made the Union position on Cemetery Hill untenable . However , Jubal Early opposed the idea when it was reported that Union troops ( probably Slocum ' s XII Corps ) were approaching on the York Pike , and he sent the brigades of John B . Gordon and Brig . Gen . William " Extra Billy " Smith to block that perceived threat ; Early urged waiting for Johnson ' s division to take the hill . After Johnson ' s division arrived via the Chambersburg Pike , it maneuvered toward the east of town in preparation to take the hill , but a small reconnaissance party sent in advance encountered a picket line of the 7th Indiana Infantry , which opened fire and captured a Confederate officer and soldier . The remainder of the Confederates fled and attempts to seize Culp ' s Hill on July 1 came to an end . Lee ' s order has been criticized because it left too much discretion to Ewell . Numerous historians and proponents of the Lost Cause movement ( most prominently Jubal Early , despite his own reluctance to support an attack at the time ) have speculated how the more aggressive Stonewall Jackson would have acted on this order if he had lived to command this wing of Lee ' s army , and how differently the second day of battle would have proceeded with Confederate artillery on Cemetery Hill , commanding the length of Cemetery Ridge and the Federal lines of communications on the Baltimore Pike . Stephen W . Sears has suggested that Gen . Meade would have invoked his original plan for a defensive line on Pipe Creek and withdrawn the Army of the Potomac , although that movement would have been a dangerous operation under pressure from Lee . Most of the rest of both armies arrived that evening or early the next morning . Johnson ' s division joined Ewell and Maj . Gen . Richard H . Anderson ' s joined Hill . Two of the three divisions of the First Corps , commanded by Lt . Gen . James Longstreet , arrived in the morning . Three cavalry brigades under Maj . Gen . J . E . B . Stuart were still out of the area , on a wide - ranging raid to the northeast . Gen . Lee sorely felt the loss of the " eyes and ears of the Army " ; Stuart ' s absence had contributed to the accidental start of the battle that morning and left Lee unsure about enemy dispositions through most of July 2 . On the Union side , Meade arrived after midnight . The II Corps and III Corps took up positions on Cemetery Ridge , and the XII Corps and the V Corps were nearby to the east . Only the VI Corps was a significant distance from the battlefield , marching rapidly to join the Army of the Potomac . The first day at Gettysburg — more significant than simply a prelude to the bloody second and third days — ranks as the 23rd biggest battle of the war by number of troops engaged . About one quarter of Meade ' s army ( 22 , 000 men ) and one third of Lee ' s army ( 27 , 000 ) were engaged . Union casualties were almost 9 , 000 , Confederate slightly more than 6 , 000 .