Francis Lieber

Francis Lieber (Franz Lieber, 18 March 1798 –2 October 1872) was a jurist and political philosopher commissioned by the U.S. Army to write the ''Instructions for the Government of the Armies of the United States in the Field'' (General Orders No. 100, 24 April 1863), the Lieber Code of military law that governed the battlefield conduct of the Union Army during the American Civil War (1861-1864).

The Lieber Code was the first codification of the customary law and the laws of war governing the battlefield conduct of an army in the field, and later was a basis for the Hague Conventions of 1899 and 1907 and for the Geneva Conventions. Provided by Wikipedia