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Lincoln Changes the Rules of War

By John Fabian Witt
6/12/2017 • American History Magazine

In the summer of 1862, President Abraham Lincoln was as “inconsolable as I could be and live.” General George McClellan had bungled an opportunity to capture the Confederate capital at Richmond and the Army of the Potomac was now in full retreat. The fate of the Union hung in the balance as Lincoln pondered what to do next.

IN JULY, LINCOLN TRAVELED TO HARRISON’S Landing cautious general. McClellan, anticipating Lincoln would blame him for not pressing an all-out offensive on Richmond, greeted him with a prepared statement on the standards of civilized war. on Virginia’s James River to meet with his  McClellan’s letter was a near perfect summary of the rules of war as perceived by both Union and Confederate officers trained at West Point. The current conflict, McClellan wrote, “should be conducted upon the highest principles known to Christian Civilization.” It “should not be a war looking to the subjugation” of a people, but rather a war “against armed forces and political organizations.” Most important, “neither confiscation of property” nor the “forcible abolition of slavery should be contemplated for a moment.”

The letter had a powerful effect on Lincoln, but not the one McClellan intended. Five days later, Lincoln confided to Secretary of State William Seward and Secretary of the Navy Gideon Welles his conclusion that liberating the slaves “was a military necessity absolutely essential for the salvation of the Union.” Emancipation could help cripple the economic foundation of the South. It might also inspire freed slaves to provide support or even fight for the Union Army. The next week, Lincoln dropped his bombshell in a Cabinet meeting. He proposed “as a fit and necessary military measure” for restoring the Union that “all persons held as slaves” within the Confederacy on January 1, 1863, “shall then, thenceforward, and forever, be free.”

We celebrate the Emancipation Proclamation 150 years later as the beginning of the end of slavery in America. But it also marks a generally overlooked turning point in the history of warfare. At the Union Army’s nadir, Lincoln chose to abandon what he called the “rose water” approach to war, advocated by McClellan and others, in favor of a more aggressive strategy that his critics and supporters alike feared might lead to a slave uprising and an indiscriminate bloodbath. To help justify that strategy, the Lincoln White House turned to Francis Lieber, a Prussian-American legal scholar, to draw up a code of laws for armies in battle.

The code Lincoln approved soon after he issued the Emancipation Proclamation is the foundation of the modern laws of war, including the Geneva Conventions of 1949. In it, Lieber drew a sharp distinction between men at arms and noncombatants, and included humanitarian provisions that protected prisoners and prohibited torture and assassinations. But he also validated Lincoln’s decision to wage a less constrained war. The code authorized the destruction of civilian property, the trapping and forced return of civilians to besieged cities, and the starving of noncombatants. It permitted summary field execution of enemy guerrillas. Essentially, the code provided Lincoln a rationale for using almost any measure necessary to secure the ends of war. “To save the country,” Lieber wrote, “is paramount to all other considerations.”

Lincoln and Lieber’s code of war was not just a list of prescriptions. It was a way to advance the Emancipation Proclamation and arm the 200,000 black soldiers who would help end slavery once and for all. It summed up tensions that have been inherent in the law of war in American history from the Revolution to the present. And during the past century and a half, the rules of war embodied in that code have been tools for vindicating the destiny of the nation.


NO NATION IN THE HISTORY of the world has made rules governing the conduct of armies in war more central to its founding self-image than the United States. In the fiery peroration of the Declaration of Independence, Thomas Jefferson charged that George III had “plundered our Seas” and “ravaged our Coasts, burnt our Towns, and destroyed the Lives of our People.”

During the Revolution, George Washington ordered the distribution of Articles of War to every soldier under his command and required that each man sign a copy of rules that included provisions designed to limit harm to civilians. He also issued frequent warnings to his soldiers not to pillage sites they captured. On New Year’s Day 1777, days after the Continental Army’s celebrated Christmas Day crossing of the Delaware and victory at Trenton, he issued an order prohibiting the plunder of “any person whatsoever,” loyalist or revolutionary. “Humanity and tenderness to women and children,” he told his men, would “distinguish brave Americans” from the “infamous mercenary ravagers” of the British forces.

In the Virginia constitution, written a month after the Declaration of Independence, Jefferson accused King George of war crimes, saying he induced “our negroes to rise up against us.” The catalyst for this indictment was a proclamation a year earlier by the fourth earl of Dunmore, the last royal governor of Virginia, which sent tremors through the colony’s plantations. “All indentured Servants, Negroes, or others” belonging to rebels, Dunmore announced, would be freed if they were “able and willing to bear arms” for the British. General Henry Clinton, the commander of the British Army, later expanded the declaration to all rebellious colonies, and over the course of the American Revolution some 20,000 slaves made their way to British camps and served as laborers or soldiers.

From the perspective of Jefferson and other founders, the liberation and arming of slaves in war was the ultimate sign of British savagery. The bloody slave insurrections in Haiti following the American Revolution heightened fears in the young republic that turning slaves against their masters in wartime could lead to mass slaughter and atrocities. In the War of 1812, Chesapeake planters were terrified when the British commandeered slaves and used them as guides and soldiers in subsequent raids on their old plantations. When John Quincy Adams negotiated peace between Britain and the United States in the Treaty of Ghent in 1814, he spluttered in indignation at these British incursions upon the plantations of the South. Slaves, he said, were private property, and American slaveholders were thereby “entitled by the laws of war” to protest against their capture and emancipation at the hands of British soldiers.

Abortive slave uprisings during the antebellum years, ranging from the shadowy conspiracy led by a Virginia slave named Gabriel in 1800 to Nat Turner’s Rebellion in 1831, fanned fears that the suppressed fury of slaves might burst into the open with the outbreak of civil war. Union leaders understood the risks at issue. From the moment Confederate batteries fired on Fort Sumter in April 1861, Lincoln insisted the war was about saving the Union, not freeing the slaves. Even into the summer and fall of 1862, many of his military commanders and close advisers worried that turning slaves against their masters during the war could lead to horrific violence.

Indeed, when Lincoln told his Cabinet he planned to issue an emancipation proclamation, they counseled caution. Secretary of State Seward, a strong antislavery man, argued that issuing such a decree from a position of weakness would look desperate and, Lincoln later recalled, “would be considered our last shriek.” At Seward’s urging, Lincoln put off moving forward with the plan for emancipation until after a Union victory on the battlefield. That grim victory finally came amid 22,700 combined Union and Confederate casualties at Antietam on September 17—the deadliest single day of the war.

The Emancipation Proclamation overturned 90 years of tradition among both Southerners and Northerners of trying to remove slaves from the calculus of war. Lincoln could have taken the opportunity to disavow the laws of war altogether, to insist that the slaveholding South had no legitimate claim to the privileges of a civilized sovereign state. But he did not. Instead of abandoning the law, he chose to transform it. The code he approved recharacterized emancipation not as anathema to the laws of civilized war but required by them.


FRANCIS LIEBER, THE POLITICAL EXILE from Prussia who drafted the code, knew war as well as anyone of his generation. In 1815, he had been shot in the neck and left for dead on the field as he and his comrades chased Napoleon back to Paris during the Waterloo Campaign. In the 1820s, he joined romantic adventurers like Lord Byron in fighting for Greek independence against the Turks, and later fled Europe for the United States, where he settled in South Carolina and then eventually moved to New York. When the Civil War began in 1861, his three sons split their allegiances between North and South. His oldest boy, Oscar, fought with a South Carolina unit known as Hampton’s Legion until he was killed in the spring of 1862, cursing his father from his deathbed as a traitor to the South. A second son, Hamilton, lost his right arm fighting for the Union in the desperate battle at Fort Donelson in February of the same year. “War,” Lieber wrote, “has thus knocked very loudly at our door.” Lieber’s youngest child, Norman, served in the Union Army as a judge advocate.

Despite tragic personal consequences, Lieber understood that war was sometimes necessary to bring moral progress to the world. The master principle that animated his code was the same one that justified Lincoln’s Emancipation Proclamation: Virtually any use of force was permissible if required by military necessity. At least 10 provisions of the code related to emancipation or the rights of black soldiers, more than dealt with all other classic conduct of war subjects, such as torture, civilian targets, wounded soldiers, hospitals and spies, combined. Lieber’s text empowered victorious armies to abolish slavery. It defended the rights of black soldiers, insisting that the laws of war made “no distinction of color” and announcing that mistreatment of prisoners by one side licensed retaliation by the other. In early May 1863, Lincoln issued Lieber’s code as General Orders No. 100 to the Union Army. A Union officer in charge of prisoner exchanges shared it with his Confederate counterpart and declared that its terms would serve as the rules of war for the remainder of the conflict.


THE CONFEDERATE REACTION was instantaneous and unsparing. Secretary of War James Seddon argued that the code’s military necessity principle meant an army could either fight with “faith” and “honor” or behave like the “barbarous hordes” of the Middle Ages, committing “acts of atrocity and violence” that would “shock the moral sense of civilized nations.” Meanwhile, a controversy over black soldiers in Union uniform heated up. President Jefferson Davis had declared that the Confederacy would treat black soldiers not as prisoners of war, but as slaves in unlawful insurrection, subject to execution or re-enslavement. White Union officers in black regiments, Davis claimed, were participants in a vast conspiracy to turn the slaves of the Confederacy against their masters. They, too, would be subject to execution. Under pressure from free blacks like Frederick Douglass, Lincoln responded by reaffirming that General Orders No. 100 protected the rights of black soldiers. An additional order issued on July 31 adopted the language Lieber had first drafted to threaten retaliation for any Union soldier executed or sold into slavery by the South. Confederate soldiers in Union hands, Lincoln announced, would be executed or put to hard labor.

By supporting the Union’s position on black prisoners of war, the code of 1863 helped to shape the remaining two years of the conflict. When the Lincoln administration stood up for the rights of black soldiers, prisoner exchanges broke down irretrievably. The Confederate officer in charge of prisoner exchanges, Robert Ould, said that Southerners would “die in the last ditch” before they agreed to treat blacks as regular soldiers. With exchanges at a standstill, conditions in prisoner of war camps on both sides quickly deteriorated. Populations spiked at already overcrowded camps such as Andersonville in the South and Elmira in the North. All told, 56,000 prisoners of war died in enemy custody during the war, most of them casualties of the halt in exchanges that Lincoln’s code of war helped to bring about.

General Orders No. 100 figured in the war in other ways as well. It became, for example, a field guide for the 1,000 Civil War military commissions charging men (and a few women) with violations of the laws of war.

At the same time, Lincoln turned to the code of war to sanction the new and more forceful strategy that accompanied emancipation. In this regard, Sherman’s March to the Sea in 1864 was the practical embodiment of the new code. Lieber had authorized vast destruction when necessary to advance the war effort. Now Sherman promised to “make a wreck of the road and of the country” as he went, to destroy Atlanta, and to “cripple [the South’s] military resources,” all the while “smashing things to the sea.” Sherman was not so much betraying the laws of war as he was vindicating the vision of just wars that Lincoln had developed in the summer of 1862. For Lincoln had come to think that while just wars must observe limits, those limits could not be handcuffs. Just wars were worth winning.


IN MANAGING THE FALLOUT from emancipation, Lincoln and his administration called forth a new blueprint for war that is at the core of a complex body of international law today. These rules mark the outer boundaries of morally acceptable behavior, just as they did in Lincoln’s time—putting torture beyond the pale, for example. They have their domestic uses too. Modern presidents, Republican and Democrat alike, have invoked them to bolster expansive conceptions of the power of the executive branch in armed conflicts. They serve as the basis for the criminal prosecution of al-Qaeda members and associated forces in military commissions at Guantánamo Bay. At the same time, they help mobilize opposition to the use of force, both domestically and abroad.

Regulating warfare is always rife with unsatisfactory moral compromises. But Lincoln successfully struck a balance, not by running away from the rules of war, but by engaging them and recrafting them for the harsh realities of civil war. He did not let high humanitarian ideals obstruct his pursuit of the just end of restoring the Union. Nor did he let his commitment to winning the war overwhelm moral limits on its conduct. On the contrary, Lincoln turned this moment of distress into one of the war’s lasting legacies.


John Fabian Witt is Allen H. Duffy Class of 1960 Professor of Law at Yale Law School. His latest book is Lincoln’s Code: The Laws of War in American History.

Originally published in the February 2013 issue of American History. To subscribe, click here.

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