March 31, 1863: Halleck Instructs Grant
On March 31, 1863, Henry W. Halleck wrote an “unofficial letter” to Ulysses S. Grant “as a personal friend and as a matter of friendly advice.” As is often the case in communications between a superior and his subordinate—Halleck was general-in-chief of the Union army, Grant the commander of the Army of Tennessee—the “friendly advice” concerned serious matters: the policy of the Lincoln administration toward slavery and emancipation, the obligation of military officers to faithfully execute government policy, and the essential nature of the war against the Confederacy.
From the beginning of the conflict slaves had sought freedom by seeking refuge with the Union army. In May 1861 General Benjamin F. Butler made the ad hoc decision to shelter fugitives who fled to Union lines from their work on Confederate fortifications. His actions received legislative endorsement in August of that year when Congress passed a confiscation act emancipating slaves being used to militarily aid the rebellion. But the confiscation act provided no guidance as to how the army should treat fugitives from the border states, or escaped slaves from the seceded states whose owners professed loyalty to the Union. In March 1862, Congress adopted a new article of war prohibiting military and naval officers from returning fugitives.
Left unresolved was the question of whether the army should actively encourage slaves to come within its lines, or to what extent the Union should embrace emancipation as a means of war. Many conservative officers abhorred the notion of waging war against slavery. In a letter he presented to President Lincoln on July 8, 1862, George B. McClellan, the commander of the Army of the Potomac, insisted that “the forcible abolition of slavery” should not “be contemplated for a moment,” and warned that any “declaration of radical views, especially upon slavery, will rapidly disintegrate our present Armies.” The war, McClellan wrote, “should not be, at all, a War upon population; but against armed forces and political organizations.” When Lincoln issued the preliminary Emancipation Proclamation, McClellan described it as “inaugurating servile war” in a letter to a prominent New York Democrat.
Halleck, unlike McClellan, accepted the necessity of emancipation as a war measure, and wanted to make sure that Grant accepted it as well. Believing that his army could neither provide for nor safely transport black refugees, Grant had issued orders on February 12, 1863, prohibiting them from coming into the Union camps along the Mississippi near Vicksburg. In his “unofficial letter,” Halleck bluntly expressed what the administration now expected: “It is the policy of the Government to withdraw from the enemy as much productive labor as possible. So long as the rebels retain and employ their slaves in producing grains, &c., they can employ all the whites in the field. Every slave withdrawn from the enemy is equivalent to a white man put hors de combat.” Grant was to “withdraw from the use of the enemy all the slaves you can,” and to employ them as laborers, teamsters, cooks, and, “as far as practicable,” as soldiers. It was Grant’s responsibility to see that administration policy was carried out, irrespective of the personal opinions of the officers under his command, and to appreciate the urgent nature of the struggle they were now engaged in:
The character of the war has very much changed within the last year. There is now no possible hope of reconciliation with the rebels. The Union party in the South is virtually destroyed. There can be no peace but that which is forced by the sword. We must conquer the rebels or be conquered by them. The North must conquer the slave oligarchy or become slaves themselves—the manufacturers mere “hewers of wood and drawers of water” to Southern aristocrats.
Grant complied with Halleck’s directives, reversing his earlier instructions excluding fugitives from the army lines and energetically assisting Adjutant General Lorenzo Thomas in his efforts to recruit black troops in the Mississippi Valley. Unlike McClellan, Grant increasingly understood that the Confederacy could not be defeated by a war waged purely “against armed forces and political organizations,” but only by a war aimed at the foundations of southern society.
 Henry W. Halleck to Ulysses S. Grant, March 31, 1863, in The Civil War: The Third Year Told by Those Who Lived It, ed. Brooks D. Simpson (New York: The Library of America, 2013), 107.
 George B. McClellan to Abraham Lincoln, July 7, 1862, in The Civil War: The Second Year Told by Those Who Lived It, ed. Stephen W. Sears (New York: The Library of America, 2012), 307–308.
 George B. McClellan to William H. Aspinwall, September 26, 1862, in The Civil War: The Second Year Told by Those Who Lived It, ed. Stephen W. Sears (New York: The Library of America, 2012), 540.
 Henry W. Halleck to Ulysses S. Grant, March 31, 1863, in The Civil War: The Third Year Told by Those Who Lived It, ed. Brooks D. Simpson (New York: The Library of America, 2013), 105–106.
 Ibid., 106.
Aaron Sheehan-Dean is the Eberly Family Professor of Civil War History at West Virginia University.