Cross-posted at the blog of the Abraham Lincoln Institute for the Study of Leadership and Public Policy
Recent years have seen a number of solid historical books on the scope of war’s destructiveness and the forces that either escalate it or rein it in. Mark Grimsley’s Hard Hand of War was one of the seminal works in this scholarly conversation; other contributors have included Mark Neely and Wayne Lee. John Fabian Witt is the latest historian to examine Americans’ attempts to regulate and legitimize warfare in Lincoln’s Code: The Laws of War in American History. His portrayal of the history of rules to govern nations and individuals at war leaves the reader with the distinct impression that such rules have exacerbated warfare’s violence as often as they have reined it in.
The regulation of war has been an important force in American history from its very beginnings. The American Revolutionaries prided themselves on adherence to the mores of restrained, civilized war that were fashionable during the Enlightenment, and with independence won, the country’s leaders expended considerable effort upholding the right of neutral shipping as a component of the law of nations.
War raised legal questions involving the behavior of individual soldiers and civilians as well as countries. When American troops campaigning in Mexico found themselves subject to attack by guerrillas, and as U.S. reprisals against Mexicans threatened to escalate this conflict to frightening levels, the novel situation of dealing with military transgressions overseas led American commanders to develop important innovations, particularly the use of military commissions to try enemy personnel.
But it was the Civil War which proved to be especially fertile ground for the growth of military law. In Witt’s portrayal, Lincoln and his advisers emerge as consummate pragmatists, shifting from one set of standards for conducting war to the other depending on the Union’s particular needs at any given time. This flexibility led to some thorny contradictions; subjecting the Confederacy to a blockade was a convenient means of employing commonly recognized principles of the law of nations, but also made it difficult to prosecute blockade runners as illegitimate pirates. 
A thorough and systematic presentation of the rules governing Union armies emerged out of the messy nature of this war that was both a contest between parties claiming the status of sovereign nations and a rebellion by one section against the rest of the country. The man responsible for crafting it was Francis Leiber, a Prussian immigrant to the U.S. and military philosopher whose notions of the boundaries of proper behavior in war differed markedly from those of most eighteenth-century thinkers. Whereas Enlightenment thinkers believed that an army gained its legitimacy from its conduct rather than the cause for which it fought, Leieber argued that proper ends could legitimate extreme means. Lieber was also a proponent of the idea that sharp wars were ultimately more humane because their severity convinced a foe to yield quickly and thus saved lives, a stance shared by some of the Union’s most prominent leaders (including hard war practitioner William T. Sherman). When the Confederacy began incorporating partisan guerrillas into its regular forces, the Union government tapped Lieber to create guidelines for determining the status of prisoners. In Dec. 1862, Union authorities turned to him again, this time to craft a more comprehensive code of regulations to govern the behavior of armies in the field. The result became General Order No. 100, which turned Lieber’s notions of aggressive, pragmatic warfare into official Union policy.
This aggressive turn to the Union war effort developed alongside Lincoln’s policy of emancipation. War had been a corrosive agent against slavery since the time of the Revolution and the War of 1812, but to Americans of the time, the loss of their slaves ran counter to contemporary notions of the sanctity of civilian property in war. But the exigencies of the Civil War allowed Lincoln to take the extraordinary measure of freeing slaves in rebellious territory. This extreme act, which prompted howls of outrage from earlier Americans who saw their slaves abscond with British armies, became justifiable within the framework of an aggressive war effort because it served a laudable end. Emancipation thus conformed to Lieber’s concept of aggressive war measures legitimized by the goal in sight.
The same notion of aggressive war was practiced by Judge Advocate General Joseph Holt, who upheld Lincoln’s use of war powers and the use of military commissions to try those accused of transgressing the laws of war. Most of these commissions tried guerrillas and non-combatants instead of Union soldiers, and for a wide variety of offenses. The pragmatic philosophy of aggressive war out of military necessity also lay behind Sherman’s destructive march to the Georgia coast and then into South Carolina.
Lieber’s Code outlasted the war it was created to regulate. The expansion of the scope of military authority shaped post-war policies regarding the treatment of Lincoln’s assassins, prominent ex-Confederates, and the former Confederate states as a whole. The U.S. also found an aggressive military code useful in dealing with Indians. Whereas earlier American armies used the notion of Indians as outside the customs of civilized war to justify harsh measures against them, after the Civil War the use of military commissions legitimized the use of the death penalty against these enemies whose exact status was open to question. Thus the code gave official backing to the killing of captured foes, an act that earlier armies had handled in an extralegal manner. Similarly, American troops in the Philippines invoked the standards contained in Lieber’s code to justify an aggressive imperial war in that island nation, even as some of them transgressed that code with the use of torture, which Lieber himself had refused to include in his range of permissible behaviors. And it was not only Americans who found in the laws of war a pretext for harshness, as European statesmen used the Lieber Code as the basis for a new body of international military laws. Leaders of the strong, modern nations of the late nineteenth and early twentieth centuries balked at the notion of circumscribing their armies with strict standards of behavior, but were open to Lieber’s more aggressive approach.
Witt thus puts the evolution of war-making during the Civil War within a broad historical context, both backward into the Enlightenment and forward into the modern era. Lincoln’s Code demonstrates how the use of emancipation, military courts, the Anaconda Plan, and Sherman’s “hard war” developed out of questions that arose early in American history, and how consequential the Civil War proved to be on several different political, legal, and moral fronts.
Some of the most prominent recent scholarship on the destructive nature of the Civil War has emphasized that destruction’s limits rather than its scale; the “hard war” was an escalation, but it was neither wanton nor unrestrained. Witt’s emphasis is more on what the aggressive code of war allowed than on what it prohibited. Time and again, he explains how politicians and commanders found that laws of war actually magnified their power and the power of the armies under their authority. Laws and regulations were ambiguous in their effects; they drew lines which armies are not allowed to cross, but the very act of drawing lines legitimized behaviors on the other side of them.
The law of war, as Witt presents it, has therefore served to give official sanction to the escalation of violence as well as condemn it. In this age when American leaders are once again grappling with issues relating to soldiers, enemy combatants, and civilian populations, scholarly attention to the problem of regulating a government’s power to wage war is especially timely. Lincoln’s Code is a comprehensive, readable, and incisive examination of this problem’s historical dimensions.
