Condemnations of war are easy to find. Social critics, politicians, and even generals speak out against it. The philosopher John Stuart Mill noted that it is an “ugly thing.” Georges Clemenceau, who was Prime Minister of France during World War I, believed that war is “too serious a matter to leave to soldiers.” War is a “racket,” according to Marine Corps Major General Smedley D. Butler, who was twice awarded the Congressional Medal of Honor. But war is also fascinating and alluring. During one battle General Robert E. Lee, remarked: “It is well that war is so terrible, or we would grow too fond of it.”

War is also an integral part of human society and inherently tied to politics. One might teach most of Western history as the preparation for war, the actual war, the recovery from the war, and the preparation for the next war. In addition to the Civil War, the United States has been involved in at least thirteen major foreign wars covering about one-fifth of the nation’s history. This does not include innumerable campaigns, battles, and wars with American Indian nations. To these large-scale military conflicts we must add bellicose moments and events that involved ground and naval conflict and some casualties, but stopped just short of a full-scale war; the use of the national armed forces to suppress domestic insurrections; and numerous military adventures of varying lengths in China, Mexico, Nicaragua, Haiti, the Dominican Republic, the Soviet Union, Lebanon, Grenada, Kosovo, Libya, and elsewhere. With this history in mind, one could argue that years of peace—when no American troops were killed or killed anyone else in combat—are far less common than years in which there was lethal combat involving Americans. The United States has not declared war since World War II ended in 1945, but since then more than 100 thousand US servicemen and servicewomen have died in combat and nearly 300 thousand have been wounded.

The history of European nations is even bloodier, and if the use of European troops outside the continent in worldwide conflicts, colonial wars, insurrections, and rebellions is included, this history is more gruesome still. In just ten years (1914–1919, 1939–1945) of the first half of the twentieth century Europe itself was the scene of the slaughter of about sixty million people. Twenty-first-century Europeans praise themselves for not having had a major war for more than a half century. Europe had never achieved this level of peace in the previous millennium. But such self-congratulatory hubris ignores conflicts in Cyprus, Northern Ireland, the former Yugoslavia, Hungary, and Chechnya as well as the use of European troops in Korea, Indochina, Malaysia, Egypt, Algeria, all over sub-Saharan Africa, Kuwait, the Falklands (or Malvinas), Iraq, Afghanistan, Mali, and other places.

Military conflict is a manifestation of politics and public policy. The great military theorist Carl Philipp Gottfried von Clausewitz succinctly made the point: “War is merely the continuation of policy by other means.” Mao Tse-Tung, who understood the power of force as well as anyone, believed that “politics is war without bloodshed while war is politics with bloodshed.”

Whether seen as policy, politics, or both, as General William Tecumseh Sherman reminded the world, “War is hell.” Most modern nations, while maintaining armies and engaging in armed conflict for defense or as a “continuation of policy,” have simultaneously tried to reduce the destruction and human costs of warfare borne by both soldiers and civilians. Leaders, diplomats, generals, and scholars have also tried to develop “rules” for warfare to eliminate unnecessary violence, destruction, and suffering, and to protect, as much as possible, the lives and property of noncombatants. The law of war has also incorporated rules to protect the lives of captured soldiers and regulate their treatment, ban the use of some kinds of weapons (such as poisons, small explosive projectiles, mustard gas, or serrated bayonets), and prohibit certain kinds of behavior (such as shooting at someone under a flag of truce when forces are not engaged in combat, torture, and targeted assassinations).

The law of war was developed to rein in the horror of war— to make it less “hell[ish],” in Sherman’s terms. But ironically these humanitarian restraints have condoned massive destruction of property and the killing of large numbers of human beings. As George C. Scott succinctly put it in his brilliant cinematic portrayal of General George S. Patton, “No bastard ever won a war by dying for his country. He won it by making the other poor dumb bastard die for his country.” War in the end is about making the other “poor bastards” die for their country. The law of war is about regulating the carnage, controlling and reducing the horror, and limiting the destruction. But the law of war neither prevents nor condemns war per se, and thus condones, or at least allows, much of the killing or the devastation that goes with it.

in the context of Professor John Fabian Witt’s recent book, Lincoln’s Code: The Laws of War in American History. The heart of this book focuses on the American Civil War, and especially on the first serious attempt to provide a practical code for the law of war—Francis Lieber’s short tract, Instructions for the Government of Armies of the United States in the Field, better known as the Lieber Code. Lieber wrote the Lieber Code (he was technically part of the committee but everyone agrees it was his work) at the request of Major General Henry W. Halleck, the general-in-chief of the United States Army. The document was “approved by the President of the United States,” and then issued by the War Department as General Order No. 100. The War Department distributed copies to all officers. While written as a Civil War regulation, the Lieber Code remained in force into the twentieth century and became the basis of future international agreements on the law of war. Thus, while the Lieber Code is at the heart of Professor Witt’s project, his book offers much more, including a serious and significant history of the law of war in the preceding centuries.

Let me start out by noting that this is an elegantly written, engaging book with an enormous amount of terrific information and analysis. I have some major disagreements with Witt on some issues, and as I set out in Part VI of this Review, I believe he misunderstands Lincoln on emancipation and fails to consider the importance of the Constitution in shaping both emancipation and the Lieber Code. Similarly, as I set out in Part VIII, I think Witt incorrectly blames the Lieber Code for the horrendous behavior of the United States Army in the years after the Civil War. But, despite these reservations, I think this is a must read for anyone interested in the law of war, the history of warfare, or modern issues of warfare and terrorism. It ought to be required reading in courses dealing with public international law and issues of war and peace.

My goal in the rest of this Review is to explain the significance and the content of the Lieber Code, to place it in the context of both the American Civil War and the development of the modern law of war, and to offer an analysis and critique of Professor Witt’s work. Slavery is central to Witt’s book and to my argument here. Witt argues that slavery was a driving force in American foreign and military policy from the Revolution to the Civil War (p 77). He further argues that it was a central part of the Lieber Code (p 227). Witt is right on both counts, although he surprisingly never comes to terms with why slavery was central to American policy. Nor does he ever grapple with the constitutional issues that limited Lincoln’s options on emancipation. In the end, slavery helped shape the Lieber Code, but in ways that are more complicated than Witt describes.

While Witt argued that slavery was the motivation for the Lieber Code, as I note later in this Review, this overstates the case. Those who commissioned the code—most notably General Henry W. Halleck—were concerned with many issues of how to regulate an American army marching across the southern United States. The Lincoln War Department was deeply concerned about the treatment of prisoners of war, the disposition of civilian (nonslave) property, and maintaining discipline in the army. Finally, beyond slavery the administration was deeply concerned about the treatment of captured black soldiers and the behavior of its army—and the Confederate army—towards civilians.