German-born U.S. political philosopher and jurist, best known for formulating the “laws of war.” His Code for the Government of Armies in the Field (1863) subsequently served as a basis for international conventions on the conduct of warfare.

Lieber was educated at the university at Jena. A liberal political activist, he was twice imprisoned under the Prussian government. He fled to England and, in 1827, immigrated to the United States. There he began to compile and edit the first edition of the Encyclopedia Americana (1829–33). He was appointed professor of history and political economics at South Carolina College (Columbia) in 1835 and joined the faculty of Columbia College, New York City, in 1857. During this period he produced two of his most important works, Manual of Political Ethics, 2 vol. (1838–39) and On Civil Liberty and Self-Government, 2 vol. (1853). In his Code for the Government of Armies, drafted for the Union Army during the U.S. Civil War, Lieber recognized the need for a systematic, institutionalized code of behaviour to mitigate the devastation of war, protect civilians, and regulate the treatment of prisoners of war.