General Orders, No. 100

Published by the U.S. War Department in the middle of the Civil War, General Orders, No. 100 is regarded by many historians as the world's first official set of ethical guidelines about military conduct in the field. It is credited with influencing the subsequent development of international law about the rules of war.

The driving force behind General Orders, No. 100 was Francis Lieber, a German American professor of law at Columbia College (now Columbia University). In August 1862, Union general in chief Henry W. Halleck asked Lieber for his views on guerrilla warfare. Lieber obliged him with a thick manuscript that, predictably given both his strong proUnion sympathies and the existing laws and customs of war, stacked the deck against guerrilla tactics. According to Lieber, “Partisans”—officially authorized troops who merely adopted irregular tactics—were entitled to be treated as ordinary belligerents only if they carried their weapons openly and wore distinguishing identification (such as armbands). But “self-constituted guerrillas”—i.e., nearly all of them—were simply “freebooters,” “brigands,” or “assassins,” and entitled to nothing but execution. Halleck thanked Lieber for the treatise and ordered 5,000 copies for distribution to the Union Army. The treatise provided legal justification for the retaliatory tactics that Union field commanders had already begun to adopt.

In November 1862 Lieber wrote Halleck urging creation of a comprehensive set of guidelines for Union armies. Halleck responded by creating a committee consisting of Lieber and four generals, but the generals let Lieber do all the work. The result, published by the adjutant general's office on April 24, 1863, as General Orders, No. 100, was entitled, “Instructions for the Government of Armies of the United States in the Field.” It ran to 9,000 words and was divided into 10 sections. Six of these addressed guerrilla activity, flags of truce, surrender, prisoner exchange, and the like. Another condemned “assassination,” proclaiming a combatant or individual to be an “outlaw” and authorizing his death without due process. The rest covered such broad issues as military necessity, protection of noncombatants, war crimes, and the definition of insurrection, civil war, and rebellion.

[Page 305]“Military necessity,” the code asserted, “consists in the necessity of those measures which are indispensable for securing the ends of the war, and which are lawful according to the modern law and usages of war,” and specifically included “all destruction of property … and of all withholding of sustenance or means of life from the enemy; of the appropriation of whatever an enemy's country affords necessary for the subsistence and safety of the Army.” Citizens of an enemy country, it continued, were themselves enemies, and as such were subject to “the hardships of the war” (Hartigan, 48, 49).

Noncombatants were to be protected in their persons and “strictly private property” but this rule did not interfere with “the right of the victorious invader to tax the people or their property, to levy forced loans, to billet soldiers, or to appropriate property, especially houses, lands, boats or ships, and the churches, for temporary and military uses” (Hartigan, 52).

In its definition of the terms insurrection, civil war, and rebellion, the order explained that a rebellion was “an insurrection of large extent, and is usually a war between the legitimate government of a country and portions of provinces of the same who seek to throw off their allegiance to it and set up a government of their own” (Hartigan, 70). For that reason, in the parlance of General Orders, No. 100, the Civil War is officially known as “The War of the Rebellion.”

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