“The Genesis of This Little Tablet with My Name”: Francis Lieber and the Wartime Origins of General Orders No. 100

A war in Mexico left Francis Lieber estranged from Charles Sumner. Fifteen years later, another war rekindled their relationship. For nearly forty years, the two men carried on a close friendship and voluminous correspondence—one that began in 1834, long before Massachusetts elected Sumner to the Senate or the German American jurist Lieber settled at Columbia College in New York City. But when on July 4, 1845, Sumner delivered a pacifist harangue against any potential military action against Mexico, Lieber (who eventually opposed the Mexican-American War) dismissed it as “one of the worst reasoned speeches I have ever heard.” Lieber did not hide his opinions from Sumner. Their friendship quickly deteriorated, and for a time they suspended their correspondence altogether. But in late 1860, Lieber, the fierce nationalist, and Sumner, the stalwart abolitionist and Radical Republican, found themselves warmly united again in the Union’s impending war with the Confederacy.¹

Lieber made his greatest contribution to the Union war effort as the principal drafter of one of the more remarkable documents to emerge from the war, Instructions for the Government of Armies of the United States in the Field, promulgated on April 24, 1863, as General Orders No. 100, a succinct and useable summary of the laws of war. A lifetime of study prepared Lieber to draft the code that came to bear his name; the immediate inspiration to do so arose from contingent events on the battlefield throughout the opening eighteen months of the war.² But what exactly motivated Lieber to pester the Lincoln administration to provide Union armies a guide to the laws of war and then, after getting what he asked for, to take up his pen to produce his code?

Unvarnished firsthand accounts of motivations are often hard to come by, but Lieber provided one to his friend Charles Sumner less than a month after the code’s issuance:

The genesis of this little tablet with my name is this: When the war broke out, our government hesitated to exchange prisoners of war fearing that it would amount to an acknowledgement of the rebels. I wrote an article in the Times, to show that this was not the case. At the same time I concluded the lecture on the law of war in the law school. Then came the abuse of flags of truce, the arrogant pretensions of the enemy to lay down absurd rules of the law of war, and then the “guerrilla” business and confusion of ideas. Gen Halleck called upon me, after my correspondence with him, to write a pamphlet on guerrillas, which I did. The fearful abuse of paroling, becoming a premium on cowardice, went on. The Harpers Ferry affair happened. At last I wrote to Halleck that he ought to issue a Code on the Law of Nations so far as it relates to the armies in the field. I was approached, and here is the thing.³

Lieber’s substantial wartime correspondence with Union political and military leaders corroborates what he explained here explicitly. The true “genesis” of his effort to create for soldiers a set of guidelines of just conduct drawn from the laws of war were the three major concerns mentioned in his May 1863 letter to Sumner: prisoner exchanges, guerrilla warfare, and the parole.

The recent literature on Lieber and General Orders No. 100, however, offers a starkly different account of the code’s “genesis” than the one Lieber set forth to Charles Sumner. In this retelling, the inspiration for Lieber’s code rested foremost in emancipation.⁴ As John Fabian Witt argues, “it was the crisis of slavery and emancipation that called forth the Union’s law of war instructions. . . . [I]t was Lincoln’s Emancipation Proclamation that required [the code’s] production.” When Abraham Lincoln committed the Union to emancipation as policy, he “threatened to undermine the very moral structure of just wars” in the preexisting American tradition, Witt explains. Just wars were not supposed to target slavery. It was left for Lieber and others...