Lieber Code Definition: The 1863 military code of conduct written by Francis Lieber at the request of US President Abraham Lincoln. Formally known as the Instructions for the Government of Armies of the United States in the Field.The author of this army field manual was Dr. Francis Lieber; thus the name commonly given to the manual. According to George Davis:"The efforts of Dr. Lieber were so far in advance of the times that the conferences at The Hague held over a generation later, could only approve and adopt his work, without adding materially to its humane requirements."Some of the innovations include a definition for prisoner of war and a prohibition of assassination. References:Davis, George, The Prisoner of War, 7 AJIL 521 (1913), at page 530.Lieber Code, available online as of June 21, 2011, at www.civilwarhome.com/liebercode.htm Categories & Topics: Military Law Dictionary Find you are constantly looking up definitions? Try our search provider (works in most modern browsers) If you find an error or omission in Duhaime's Legal Dictionary, or if you have legal term suggestion, we'd love to hear from you!