One of the youngest major generals and corps commanders in the American Civil War, Henry Slocum led Union troops in many key battles of the Eastern and Western Theaters.
Henry Warner Slocum was born on September 24, 1827 in Delphi Falls, New York, approximately twenty-five miles southeast of Syracuse. He was the sixth of eleven children born to Matthew Barnard Slocum and Mary Ostrander Slocum. Matthew Slocum, a native of in Marietta, Ohio, operated a store in Delphi, to which the family home was attached. When young Henry was not helping out in the family store, he attended the public school in Delphi. Later, Slocum enrolled at Cazenovia Seminary in nearby Madison County, where he prepared for a career as a teacher.
In 1843, Slocum earned a certificate as a public school instructor and took a position as a teacher at a one-room school in nearby Woodstock. Using his wages, Slocum returned to Cazenovia, where he met and became engaged to Clara Rice. For the next four years, Slocum spent his time teaching, attending the Albany Normal School, and working at the family store.
In 1848, Congressman Daniel F. Gott secured an appointment for Slocum to the United States Military Academy. Slocum passed the entrance examination and entered the Academy on July 1, 1848. Among Slocum's classmates were future Union generals, George Crook, Alexander McCook, and David S. Stanley. Slocum's roommate during part of his stay at West Point was Philip H. Sheridan, who graduated one year after Slocum. During his four years at the Academy, Slocum proved to be an excellent student, graduating seventh in his class of forty-three cadets, on July 1, 1852.
Immediately following his graduation, Slocum was brevetted to second lieutenant with the 1st U.S. Artillery and sent to Florida to campaign against the Seminole Indians. Remaining in Florida only briefly, Slocum was sent with his unit to Fort Moultrie at Charleston, South Carolina in 1853. After arriving at Charleston, Slocum secured private quarters and then returned to New York, where he married Clara Rice on February 19, 1854. The couple remained married for forty years and produced four children, three of whom survived to adulthood.
Upon his return to Charleston for garrison duty, Slocum began studying law in his spare time. On March 3, 1855, he was promoted to first lieutenant. A year later, hostilities with the Seminoles erupted again. When Slocum's unit was ordered to deploy to Florida, Slocum chose to resign his commission on October 31, 1856, rather than to be separated from his family or subject them to the diseases inherent to a tropical climate.
Slocum returned to New York in 1856 and apprenticed with his brother-in-law in Syracuse, while he completed his law studies. He passed the bar examination in 1857. The next year, Slocum was admitted to the New York State Bar, and he established a law firm with his nephew, Thomas L. R. Morgan, in Syracuse. While practicing law, Slocum also began speculating in real estate and other businesses.
Opposed to slavery, Slocum became active in politics as a member of the fledgling Republican Party while living in Syracuse. On November 2, 1858, voters from the Second District elected Slocum to a seat in the New York State Assembly.
As sectional tensions increased on the national stage, Slocum joined the New York State Militia in 1859. Commissioned as a colonel, he spent the next two years training the state's soldiers in artillery tactics.
By the end of 1859, Slocum had his fill of Albany politics. He chose not to run for reelection to the state legislature. Instead, he returned to Syracuse, where voters elected him to the office of Onondaga County Treasurer. He served in that office until the beginning of the Civil War, when the men of New York's 27th Infantry Regiment elected him as their colonel. He received his commission on May 21, 1861.
The unit was mustered into service in the volunteer army on July 5, 1861 and ordered to Washington, D.C., in time to participate in the Battle of Bull Run I (July 21, 1861). During the battle, Slocum was seriously wounded in his right thigh, forcing him to be hospitalized. He then returned home for six weeks of recuperation. While he was away from his regiment, Slocum was promoted to major general of volunteers on August 9, 1861.
Slocum rejoined his unit in Washington on September 10, 1861. During Major General George B. McClellan's Peninsula Campaign (March 17–August 14, 1862), Slocum commanded the 2nd Brigade of the 1st Division of the 1st Corps of the Army of the Potomac from March until May. During the early part of the campaign, Slocum was engaged at the Siege of Yorktown (April 5-May 4, 1862). In May, he was placed in command of the 1st Division of the 6th Corps. During the Seven Days Battles, Slocum's men were engaged during the Battle of Gaines' Mill (June 27, 1862), the Battle of Glendale (June 30, 1862), and the Battle of Malvern Hill (July 1, 1862). On July 4, 1862, Slocum was promoted to major general. At thirty-four years of age, he was one of the youngest major generals in the Union army during the war.
At the conclusion of the Seven Days Battles, President Lincoln and General-in-Chief-of-Army Henry Halleck recalled the Army of the Potomac from the Virginia Peninsula on August 3, 1862. A few weeks later, Slocum's division covered the retreat of Major General John Pope's Army of Virginia, following the Confederate victory at the Battle of Bull Run II (August 28 to 30, 1862).
Emboldened by the Rebel victory at the Second Battle of Bull Run (August 28 to 30, 1862), Confederate commander Robert E. Lee decided to take the war to Northern soil in the late summer of 1862. On September 4, the Army of Northern Virginia began crossing the Potomac River, entering Maryland. On September 14, 1862, Slocum's division attacked D.H. Hill's division guarding Crampton's Gap through South Mountain. The Yankees quickly seized the gap and sent the Rebel defenders scurrying down the western side of the mountain. Despite Slocum's success, his wing commander, Major General William B. Franklin, did not follow up on the Union victory in time to deter Lee's advancement through Maryland.
At the Battle of Antietam (September 17, 1862), Major General George McClellan, commander of the Army of the Potomac, held Slocum's division in reserve. During the bloody engagement, the 12th Corps commander, Brigadier-General Joseph K. Mansfield, was mortally wounded. One month later, on October 15, 1862, Slocum was assigned to replace Mansfield as 12th Corps commander. At thirty-five years of age, Slocum became one of the youngest corps commanders in the volunteer army during the war.
In January 1863, Major General Joseph Hooker replaced Burnside as commander of the Army of the Potomac. In late April, Hooker divided his army into wings and initiated a plan to get to the rear of the Army of Northern Virginia. He placed Slocum in charge of the army's right wing, consisting of the 5th, 11th, and 12th Corps. On April 26, the right wing crossed the Rappahannock and Rapidan Rivers. The left wing crossed the Rappahannock River downstream and entrenched when it encountered bad weather and nearly impenetrable thickets. Upon seeing the Union left wing stopped, Lee decided to send the bulk of his army against Slocum's wing. On May 2, Stonewall Jackson marched his corps of approximately twenty-eight thousand men around Hooker's right flank. Late in the afternoon, Jackson's troops slammed into the unsuspecting Union army, and the entire right flank collapsed within a quarter of an hour. Despite the huge numerical superiority of his army, Hooker became unnerved and ordered his troops to fall back. Slocum's wing suffered a significant number of casualties at the Battle of Chancellorsville, losing nearly thirty percent of its soldiers. Convinced that Hooker's ineptitude was responsible for the severe casualties, as well as for losing the battle, Slocum joined a group of Hooker's subordinates who lobbied for Hooker's dismissal.
Hooker's waning support and stubborn personality soon led to his demise. On June 28, 1863, Hooker attended a strategy meeting with President Lincoln and General-in-Chief Henry W. Halleck. When a dispute arose regarding the disposition of troops at Harper's Ferry, Hooker offered to resign his command. Lincoln quickly accepted Hooker's resignation as commander of the Army of the Potomac and selected Major General George G. Meade to replace him. Slocum's relatively young age may have been a major factor in convincing the president to pass over Slocum despite the fact that Slocum outranked Meade in seniority (Slocum was promoted to major general on July 4, 1862-–Meade achieved the rank on November 29, 1862).
Slocum's first test under Meade's command came at the Battle of Gettysburg (July 1-July 3, 1863). His actions on the first day of the engagement left him open to criticism from his peers and, later, from historians. While marching his corps toward Gettysburg, Slocum stopped at a prearranged site approximately five miles southeast of town on the morning of July 1, despite claims from subordinate officers that there was clear evidence that a battle was being waged. Starting at 1:00 p.m., Slocum received several requests from Major General Oliver O. Howard to advance to Gettysburg in support of the 11th Corps, which was heavily engaged. Slocum vacillated and did not proceed to Gettysburg until late in the afternoon, despite the fact that he would have been the senior general on the battlefield. As a result, Slocum did not reach the town and take control of the forces there until nearly 6:00 p.m.–-after the 11th Corps had suffered heavy losses. His dilatory behavior later earned Slocum the derogatory nickname, "Slow Come."
Slocum commanded the troops at Gettysburg until approximately midnight, when Meade arrived on the scene. During the remainder of the battle, Slocum and his men performed admirably. On the afternoon of July 2, when Meade ordered Slocum to deploy all of the 12th Corps to the Union right, Slocum convinced Meade to allow him to keep one brigade on Culp's Hill. The decision later proved to be beneficial, as Brigadier-General George S. Greene's brigade withstood several spirited Confederate assaults on the strategic elevation.
Following the Union victory at the Battle of Gettysburg, the 11th and 12th Corps were detached from the Army of the Potomac. They were sent west under the command of Major General Joseph Hooker in support of the Army of the Cumberland, which was under siege at Chattanooga, Tennessee, following the Confederate victory at the Battle of Chickamauga (September 19-20, 1863). Still sour from his experience at Chancellorsville, Slocum met with President Lincoln on September 28, 1863 and threatened to resign his commission if forced to serve again under Hooker. Sensitive to the possibility of losing a valued general, Lincoln assured Slocum that he would be given a command independent of Hooker. The result was that Slocum was ordered to guard the Nashville & Chattanooga Railroad with one division of the 12th Corps. The remainder of the 12th Corps fought with Hooker during the Chattanooga Campaign.
On April 27, 1864, with the endorsement of William T. Sherman and Ulysses S. Grant, Slocum was assigned to command the Military District of Vicksburg. He held that position until August, when he received command of the 20th Army Corps following the death of Major General James B. McPherson during the Battle of Atlanta. When the Georgia capital fell into Union hands on September 2, 1864, Slocum's troops were the first to enter the city.
After occupying Atlanta, Sherman received approval from Grant to embark upon the “March to the Sea” that would make “Georgia howl.” On November 9, 1864, Sherman issued Special Field Orders No. 120, establishing the chain-of-command, objectives, and directives for the Savannah Campaign. Sherman divided his forces into two wings. Slocum commanded the left wing, which consisted of the 14th and 20th Corps, along with part of the Army of the Cumberland's cavalry. These men met little resistance as they cut a swath of destruction from west to east across Georgia and captured the city of Savannah on December 21.
On February 1, 1865, Sherman embarked on a campaign through the Carolinas with the objective of cutting off supplies and reinforcements to Robert E. Lee's Army of Northern Virginia facing Grant's Army of the Potomac near Richmond, Virginia. Once again, Slocum's forces served as the left wing of Sherman's army group.
On March 16 1865, Slocum's men attacked General Joseph Johnston's entrenched Rebels north of Averasboro, North Carolina. Slocum's soldiers flanked the Confederates, forcing them to withdraw to a second defensive line. The Grey Coats made a brief stand at the second line, before falling back to their third and final line of defense. Despite several Union assaults, the Confederates held their position until nightfall and, then, withdrew to Bentonville under the cover of darkness.
By mid-March, Johnston had assembled an army of perhaps twenty-one thousand soldiers at Bentonville. On March 19, 1865, Johnston decided to make a stand, entrenching his army at Cole's Plantation, blocking the road to Goldsboro. Once again, Slocum's wing was the target. That afternoon, Johnston launched an assault on the Federals, forcing them to fall back temporarily. By nightfall, Slocum's men checked the Rebel advance, and the first day of fighting at the Battle of Bentonville ended in a stalemate. On the next day, Federal reinforcements arrived, and Slocum gradually pushed Johnston's men back. Johnston held on until March 21, when he withdrew during the night.
A few days after the Battle of Bentonville, Sherman contacted General Grant requesting that Slocum's wing (the 14th and 20th Army Corps) be separated from the Army of the Cumberland and designated as the newly created Army of Georgia. On March 28, 1865, the War Department issued General Orders No. 51 granting Sherman's request. The Army of Georgia went on to occupy Goldsborough and to capture Raleigh in April. Slocum was also present on April 16, 1865, when Johnston surrendered the troops under his command to Sherman near Durham, North Carolina.
After Johnston's surrender, Slocum went on to lead the Army of Georgia during the Grand Review of the Armies in the nation's capital in May 1865. Afterwards, he returned to New York on leave, before briefly commanding the Department of the Mississippi from June 29 to September 16, 1865.
On September 28, 1865, Slocum resigned from the army and returned to his home state and settled in Brooklyn, where he resumed his law career. In November 1868, voters of New York's Third District elected Slocum to a seat in the U.S. House of Representatives as a member of the Democratic Party. Slocum served in the 41st and 42nd Congresses (March 4, 1869-March 3, 1873) but was not a candidate for reelection in 1872. Instead, Slocum returned to New York, where he founded the Brooklyn Crosstown Railroad, which later became the Brooklyn and Coney Island Railroad Company. In 1876, Slocum received an appointment as president of New York's department of city works. He served in that office until 1883, when he returned to the House of Representatives for the 48th Congress (March 4, 1883 to March 4, 1885) as an at-large representative from New York.
In 1893, Slocum retired as president of the Brooklyn and Coney Island Railroad Company. One year later, he contracted a case of pneumonia in early April. Slocum died of heart failure caused by this illness on April 14, 1894 at his home in Brooklyn. His remains were interred at Greenwood Cemetery in the same city.
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"Henry Warner Slocum," Ohio Civil War Central, 2021, Ohio Civil War Central. 31 Jul 2021 <http://www.ohiocivilwarcentral.com/entry.php?rec=1307>
"Henry Warner Slocum." (2021) In Ohio Civil War Central, Retrieved July 31, 2021, from Ohio Civil War Central: http://www.ohiocivilwarcentral.com/entry.php?rec=1307
- Ambrose E. Burnside
- Army of Georgia
- Army of Northern Virginia
- Army of the Cumberland
- Army of the Potomac (USA)
- Army of Virginia
- Battle of Antietam
- Battle of Atlanta
- Battle of Bentonville
- Battle of Bull Run I
- Battle of Chancellorsville
- Battle of Gaines' Mill
- Battle of Gettysburg
- Battle of Malvern Hill
- Chattanooga Campaign
- David S. Stanley
- General Orders, No. 181 (U.S. War Department)
- General Orders, No. 238 (U.S. War Department)
- General Orders, No. 5 (U.S. War Department)
- General Orders, No. 51 (U.S. War Department)
- General Orders, No. 96 (U.S. War Department) (1863)
- George B. McClellan
- George Crook
- George G. Meade
- Henry W. Halleck
- James B. McPherson
- Joseph Hooker
- Oliver O. Howard
- Peninsula Campaign
- Robert E. Lee
- Savannah Campaign
- Seven Days Battles
- Siege of Yorktown
- Ulysses S. Grant
- William B. Franklin
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