UNION TWELFTH CORPS 20 guns/9,534 men

Henry Slocum was only thirty-six years old, young for a major general, yet at Gettysburg he was the ranking general on the field--even senior to the army's commander, Maj. Gen. George Meade. Physically, he was "small and rather spare, with black straight hair, and beard, which latter is unshaven and thin, large full, quick black eyes, white skin, sharp nose, wide cheek bones, and hollow cheeks and small chin. His movements are quick and angular,--and he dresses with a sufficient degree of elegance," according to Frank Haskell, who sketched him thus at the generals' meeting at Gettysburg. He wore his long hair combed back behind his ears, and had a heavy brown mustache. His manner "inspired faith and confidence," according to those around him, and one noted that his sparkling brown eyes gave him a "magnetic power over his troops." He had risen far on these charismatic qualities in the first two years of the war.

Those qualities, however, masked a careful, even cautious nature. Self-contained and unemotional, a man who loved discipline and order, Slocum was attentive to detail and protocol, sometimes agonizingly so. As a leader of men, Slocum lacked dash. He personified the Old Army way of command, never exceeding his orders. Slocum prided himself on serving throughout the war without friction, and the way he accomplished this was to always avoid assuming responsibility. There was an up-side to this style of leadership, however: in the entire war, the men serving under him never lost a stand of colors or a gun. And once he committed himself to battle, he was one of the army's hardest and toughest fighters.

His whole life had been marked by ability and activity. Slocum was born in a small town in Onondaga County, near Syracuse in upstate New York. He was a superior student, and graduated 7th out of 43 in the West Point Class of 1852, an achievement made even more impressive by the fact that he roomed with Phil Sheridan, who took a full five years to graduate. Commissioned into the artillery, he saw duty against the Seminoles and at Fort Moultrie, South Carolina. Garrison life proved irksome, so in his off hours he occupied his restless mind by studying law. In 1857 he left the army and set up a law practice in Syracuse, where he became county treasurer and state legislator, and served as a colonel of artillery in the militia. Shortly after Fort Sumter's fall, he responded to the call for soldiers and re-entered military service as colonel of the 27th New York Volunteers.

In the first major battle of the war, at Bull Run, he was severely wounded in the thigh at the head of his regiment. While he convalesced, he was promoted to brigadier general, and when the Army of the Potomac was organized into divisions in October 1861 he was put at the head of a brigade. In May 1862, when the Sixth Corps was organized, he was put at the head of its First Division, which he led with distinction in the maelstrom of Gaines' Mill near the end of June. A few days later, on July 4, 1862, Slocum was promoted to major general, at the time the second youngest in the country to attain that rank.

At South Mountain in September Slocum drew further notice when he and his officers overrode their indecisive corps commander, Maj. Gen. William B. Franklin, and charged the Rebels behind a stone wall at Crampton's Gap, routing them and taking four battle flags. Heroes were few in the Army of the Potomac in 1862, and with his Crampton's Gap success fresh in the minds of the army high command, Slocum was promoted to the head of Twelfth Corps in October, replacing General Mansfield, who had been killed at Antietam (where Slocum's division had languished in reserve). Thus, in one of the most meteoric rises of any man in the history of the war, Slocum had gone, in the space of one year from October 1861 to October 1862, from regimental commander to brigade commander to division commander to corps commander. That ascent must have been inspired mostly by Slocum's intelligence, obvious ability, and vigorous personal qualities, because in that entire period his only experience in a major battle had been at Gaines' Mill in the Seven Days.

The Twelfth Corps mercifully arrived too late for the bloodletting at Fredericksburg, so its first battle under Slocum came the following May at Chancellorsville. In fact, in the early stages of that campaign, Slocum was in charge of three corps constituting the entire maneuver element of the army, 46,000 men strong. Slocum's force flawlessly executed a flank march and slipped around and behind Lee, but were told by commanding Maj. Gen. Joe Hooker to wait at Chancellorsville. The Fifth Corps's Maj. Gen. George Meade advised an advance into the advantageous open ground beyond the Wilderness, but to do so would have exceeded Hooker's orders, and this Slocum would not do. In the tragic battle that ensued, Slocum's Twelfth Corps fought hard and well, losing nearly three thousand casualties, 21% of its men.

Slocum was highly critical of Hooker's timidity at Chancellorsville, an opinion which coincided with those in Washington. When the decision was made to change leadership before Gettysburg, it is noteworthy that Slocum, who ranked highest, was not seriously considered for the command of the army. Although he had done nothing to cast doubt on his military abilities, nothing marked him for higher responsibility, either. That post was given to Meade, and Slocum graciously consented to serve under him.

Slocum was an able, if not dashing, corps commander. He had been in command of his corps for eight months, longer than anyone except Sedgwick of the Sixth, and had experience leading his corps in battle at Chancellorsville.

At Gettysburg
Slocum's habit of maneuvering to avoid tough assignments resulted in an unfortunate incident on the first day of fighting at Gettysburg, when the senior commander on the field, Maj. Gen. O.O. Howard, sent a dispatch to Slocum to come forward with the Twelfth Corps to reinforce the outnumbered Union force. Slocum spent the entire afternoon in hesitation, neither bringing forward his corps nor going ahead himself to take command by virtue of his rank. Evidently he judged that Meade's directives for the occupation of the Pipe Creek line were being subverted by this affair near Gettysburg, which seemed to be going very badly. Heads were likely to roll, and he was taking care that his would not be among them. The messenger who brought Howard's request recorded that he thought Slocum's "conduct on this occasion was anything but honorable, soldierly or patriotic." A more aggressive general such as Reynolds, Hancock, or Sickles would have marched to the sound of the guns under these circumstances. Slocum eventually earned the nickname "Slow Come" from unseemly episodes like this one.

Slocum put his corps in motion late in the afternoon, and once on the field about 6:00 P.M., he detached Geary's division to guard the army's left on Little Round Top, detached Williams's division to the army's right around Wolf's Hill, and rode to Cemetery Hill himself, where, as ranking officer, he relieved Maj. Gens. Howard and Hancock as commander of the army on the field. He was in turn relieved when Meade arrived around midnight.

The next morning, July 2, both Twelfth Corps divisions were summoned and posted on Culp's Hill. Slocum contributed to the army's strategy when he advised against an attack Meade was considering from Culp's Hill--Slocum thought the terrain too rugged. Meade had given Slocum command of the "Right Wing" of the army--the Fifth and Twelfth Corps--to make the attack, by virtue of Slocum's seniority. When the attack was called off, however, even though there was no more use for the "Right Wing"--especially after the Fifth Corps was sent to the army's left later in the afternoon--Slocum considered himself "wing commander" for the rest of the battle, and made Brig. Gen. A.S. Williams commander of the Twelfth Corps while he himself continued in his expanded--if imaginary--role.

That afternoon, Longstreet struck hard against the Union left, and Meade summoned assistance from the Twelfth Corps on the right. Somehow between Meade and Slocum it was determined that all but one brigade should be sent to the left--a poor judgment, as it turned out. Immediately after both divisions of the Twelfth Corps had started on their way to the left, Maj. Gen. Edward Johnson's legendary Stonewall Division charged up the Culp's Hill from Rock Creek and crashed into the lone Union brigade remaining on the hill, Brig. Gen. George Greene's New Yorkers. Not able to budge Greene from the crest, they were still able to capture much of the just-abandoned Union breastworks. Slocum knew nothing of this. He was attending the generals' meeting at Meade's headquarters (where he contributed his best epigram of the war when he advised characteristically: "Stay and fight it out.") from shortly after 9:00 P.M. to midnight, and was told afterwards of the new situation. His response was another laconic gem: "Well, drive them out at daylight."

After close planning from Slocum's headquarters on Power's Hill and arduous preparation during the night, the Twelfth Corps did just that, starting with an artillery barrage at daylight on July 3, though it took all morning to force Johnson's veterans back. After the danger on Culp's Hill had passed, Slocum's job at Gettysburg was done. The action passed to the army's center for the final drama--Pickett's Charge.

Meade's report of the battle unintentionally slighted the Twelfth Corps contribution, and Slocum's reputation was not enhanced by Gettysburg. He was fortunate, however, to have avoided the recriminations that would have searched him out if the First and Eleventh Corps had not held on their own on July 1 or if Greene had not held firm on the evening of July 2.

Sent West with his corps in September, Slocum continued in positions of high responsibility for the rest of the war, eventually rising to command of the Army of Georgia under Maj. Gen. William T. Sherman.

For further reading:
Greene, A. Wilson. "Henry W. Slocum and the Twelfth Corps." in Gary Gallagher ed. The Second Day at Gettysburg, Kent, 1992
Hilton, Thomas E., ed., "To the Memory of Henry Slocum: A Eulogy by Oliver O. Howard." Civil War Times Illustrated 21, Mar 1982
Slocum, Charles E. The Life and Services of Major General Henry Warner Slocum. Toledo, 1913

Excerpted from "The Generals of Gettysburg: The Leaders of America's Greatest Battle" by Larry Tagg