Although the Civil War is generally viewed as a conflict between white Anglo-Saxon Protestants, a close examination reveals an interesting ethnic makeup among Johnny Rebs and Billy Yanks alike. Traditional groups such as the Scots-Irish and ‘Pennsylvania’ Germans could be found on both sides. Many Southern soldiers from both ethnicities in the Shenandoah Valley shared cultural, economic and kinship ties with the same groups in south-central Pennsylvania. The influx of immigrants from Germany and Catholic Ireland was well represented, particularly in the North, with units such as the Irish Brigade and the German 5th Maryland (Union) and 20th New York. All these units acquitted themselves well at Antietam.

The famed Iron Brigade boasted Germans, Norwegians and Métis (men of French Canadian and Indian descent). Indeed, recent research by Iron Brigade scholar Lance Herdegen has uncovered the existence of at least two mulattos who passed for whites and were serving in the ranks. Jews could be found in both armies. The 5th Maryland (Union), made up almost entirely of German immigrants, fought at Bloody Lane. Their commander was Major Leopold Blumenberg, a Jewish immigrant from East Prussia. Among the Confederates opposing the 5th Maryland in the Sunken Road was the 12th Alabama. Captain Adolph Proskauer, another Jewish immigrant from Prussia, served with the 12th and was seriously wounded in the battle.

Even a solid ‘Anglo’ command like the Texas Brigade had its minorities. Captain Decimus et Ultimus Barziza of Company C, 4th Texas, was the son of Italian immigrants. His name in Latin means ‘the tenth and the last’ (apparently his mother had had enough of child rearing when he came along). Both Louisiana brigades in Lee’s army were very cosmopolitan. Besides Louisiana French of both Creole and Acadian (Cajun) descent, the ranks were filled with men from all over the world. One study has shown that at least 24 nationalities were represented in these regiments, including Greeks, Italians, Mexicans, Brazilians and men from Martinique. The 12th South Carolina contained a number of Catawba Indians.

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The Army of the Potomac
McClellan’s army was put together in an amazingly short time in early September 1862 at Rockville, Md. But this new Army of the Potomac was an amalgam of a number of different commands. It was certainly not the same force that had nearly captured Richmond in the Peninsula campaign, nor was it the Army of the Potomac that would gain victory and fame at Gettysburg and other places. At Antietam McClellan had the II, V and VI corps of his original Army of the Potomac. Three corps from Pope’s ill-fated Army of Virginia were also in the fold. They became the I, XI and XII corps. While the XI Corps was kept back to guard Washington, the other two played key roles in opening the Battle of Antietam. The IX Corps was comprised of Maj. Gen. Ambrose Burnside’s unattached Carolina Expeditionary Force and the Kanawha Division.

The corps system was a Napoleonic innovation. The great emperor of France devised it as a miniature army containing three infantry divisions, artillery and cavalry. Such an organization provided simplification of command at the army level and flexibility in combat power. It was a major reason for the success of Napoleon Bonaparte’s armies. Up to the time of the Civil War, the U.S. Army had been too small to make the corps system practical. But by 1861-62 the corps had become the building block of the huge forces being raised by both sides.

The quality of command and combat efficiency made the Army of the Potomac, numbering about 86,000, a patchwork force. The average Union regiment at Antietam had 346 men. Many of the new regiments had around 800 men. Such was the case with the 125th Pennsylvania. When the 125th engaged Brig. Gen. Jubal Early’s Confederates in the West Woods, the Rebels thought that they were up against an entire Yankee brigade.

About one-fourth of McClellan’s force was made up of raw recruits. These included ‘nine-month men’ who were raised to cover the shortages caused by the War Department’s premature and overoptimistic closing of recruiting offices that summer. Eighteen of these new regiments, about 15,000 men, became part of the army just prior to the march to Antietam. Another 5,000 new recruits were added to the ranks of existing regiments as replacements. The nine-month regiments, as well as the replacements, lacked training and hindered the army by slowing it down on the march. Their ignorance of drill and firearms proved fatal at the tactical level.

McClellan’s lieutenants were a mixed lot when it came to combat experience and competence. Half of his corps commanders were new to that level of command, including I Corps commander Maj. Gen. Joseph Hooker. ‘Fighting Joe’ was a West Point graduate and one of the most aggressive commanders on the field that day. The I Corps had been part of Pope’s Army of Virginia (as the III Corps) and contained some of the best fighting units in the army, such as the famed Iron Brigade and the Pennsylvania Reserves. Excellent combat commanders could be found here, including Brig. Gen. John Gibbon, commander of the Iron Brigade; Maj. Gen. George G. Meade, later the army commander; and Brig. Gen. George Lucas Hartsuff, a veteran of the Second Seminole War.

At 65, II Corps commander Edwin V. Sumner was the oldest active corps commander in the Civil War. He had 43 years of experience in the Army, including several tours of duty in the West and distinguished service in the Mexican War. He had led the II Corps in the Peninsula campaign, where he was wounded twice. Sumner, an aggressive field commander, had the potential at Antietam to turn Lee’s left flank. But instead the iron dice of war were thrown, and luck was with the Confederates. Sumner led his 2nd Division to destruction in the so-called West Woods Massacre. His command was the largest on the field, with more than 15,000 men. This corps represented the best and the worst of the Army of the Potomac’s combat efficiency. Major General Israel Richardson led the 1st Division. Nicknamed ‘Fighting Dick,’ this veteran of the Seminole and Mexican wars was an aggressive commander. His veteran units, such as the Irish Brigade, made possible the Union breakthrough at the Sunken Road. Richardson remains one of the great ‘what ifs’ of Antietam. He was actively seeking additional troops and artillery to follow up on the breakthrough when an artillery shell mortally wounded him. The 3rd Division was commanded by Brig. Gen. William H. French, whose experience was as a brigade commander. Incredibly, this division had been put together on the march only 16 hours before the battle. Nine out of its 10 regiments had not seen any major combat.

Fitz John Porter, the V Corps commander, had great potential from the start. The New Englander ranked eighth in his West Point class of 1845 and won several brevets for gallantry in the Mexican War. Later he taught artillery at West Point and served as Albert Sidney Johnston’s adjutant in the Utah Expedition. On the Peninsula, Porter led a division of the III Corps and later the V Corps. He had success at Mechanicsville, Gaines’ Mill and Malvern Hill. Upon the withdrawal of the Army of the Potomac from the Peninsula, Porter and his corps were attached to the Army of Virginia just in time for the disastrous Second Manassas campaign. There, he was blamed by Pope for failure to provide proper support and brought up on court-martial charges. Initially relieved of command, he was reinstated through the personal intercession of McClellan with President Lincoln. For more than a century, armchair generals have believed that the V Corps could have been McClellan’s weapon of final destruction against Lee at Antietam. But the two veteran divisions of Porter’s command had suffered severe attrition both on the Peninsula and at Second Manassas. A third division, under Brig. Gen. Andrew Humphreys, was on the march to reinforce Porter, but arrived the day after the battle. Its combat effectiveness was dubious, since the entire division was made up of nine-month regiments.

Like Porter, VI Corps commander Maj. Gen. William Franklin was also up on court-martial charges for disobedience at Second Manassas. Franklin had been trained at West Point as an engineer and graduated first in the class of 1843. As the VI Corps commander, he lacked the aggression needed for combat operations. At Crampton’s Gap on September 14, 1862, his trepidation resulted in the failure to raise the siege of Harpers Ferry. Conversely, at Antietam he would unsuccessfully seek permission from McClellan to launch an attack against the Confederate left in the afternoon. Most of his men would not be engaged in the battle.

The foundation of the Union IX Corps at Antietam was Burnside’s Expeditionary Force, which had successfully conducted amphibious operations in North Carolina during the first half of 1862. This unit returned to Virginia for Second Manassas and was augmented with Brig. Gen. Jacob Cox’s Kanawha Division, which had been operating in the Kanawha Valley of western Virginia. On September 14, McClellan put his old friend Burnside in charge of the right wing of his army, consisting of the I and IX corps, leaving Maj. Gen. Jesse Reno in charge of the latter command. Upon Reno’s death at South Mountain, Cox took over temporary command of the IX Corps.

At Antietam McClellan abruptly abandoned this arrangement, sending Hooker with the I Corps toward the Confederate left flank, independent of Burnside. Thus ‘Burn,’ as he was known to friends, was left with only his old command. This rankled Burnside, and some historians believe it caused him to move sluggishly in his effort to take the stone bridge that now bears his name. The IX Corps contained many combat-seasoned units, but it also had its share of green troops. Accordingly, one of these regiments, the 16th Connecticut, wilted when Confederate Maj. Gen. A.P. Hill’s reinforcements arrived on the field. Their inexperience under fire was a factor in the collapse of Burnside’s final attack late in the afternoon.

The weakest link in McClellan’s chain of command was Brig. Gen. J.K.F. Mansfield. This 59-year-old commander had an impressive military résumé. Ranking second in the West Point class of 1822, he spent his early military career constructing defenses of the Southern coast. In the Mexican War he won several brevets for gallantry and occasionally led troops in combat. In 1853 he was appointed to the staff rank of colonel in the inspector general’s department, a position he held until the beginning of the war. When the fighting broke out, he spent most of his time on garrison duty. He was tapped to command the XII Corps two days before Antietam. This would be one of the few times he would ever lead men in battle, and the corps was the largest combat entity he had ever commanded. Mansfield did not survive his first large command. He was one of six general officers, three from each side, killed or mortally wounded at Antietam.

The XII Corps contained the largest component of nine-month regiments, five of them concentrated mostly in the 1st Brigade of the 1st Division. It was also the smallest corps in the army, fielding less than 8,000 men. These apparent deficiencies were offset by the presence of Brig. Gen. George S. Greene and his division — a seasoned command led by an experienced commander. With around 1,700 men, Greene held a pocket in the Confederate lines near the Dunker Church for more than two hours. Unsupported and low on ammunition, he ultimately was forced to abandon his position.

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