Lieber was one of the last known people to possess the infamous Dahlgren Affair papers. Shortly after obtaining them, Lieber was ordered to give them to Secretary of War Edwin M. Stanton, who likely disposed of them, as they have not been seen since. Diplomacy From 1870 until his death in New York City, aged 72, Francis Lieber served as a diplomatic negotiator between the United States and Mexico. He was chosen, with the united approval of the United States and Mexico, as final arbitrator in important cases pending between the two countries. This work was not completed at his death. Lieber was a member of the French Institute and of many learned societies in the United States and elsewhere. Family His son Oscar Montgomery Lieber was a geologist. During the Civil War, he was killed in action as a member of the Confederate army. A second son, Hamilton Lieber (7 June 1835, Philadelphia, Pennsylvania – 18 October 1876, Baden-Baden, Germany), entered the volunteer army at the beginning of the civil war as 1st lieutenant, 9th Illinois Regiment, and was badly wounded at Fort Donelson. Afterward, he was appointed a captain in the veteran reserve corps, and served during the draft riots in New York City in 1863. In 1866, he was made a captain and military storekeeper in the regular army, and was retired on account of disabilities contracted in the line of duty. A third son, Guido Norman Lieber, was a United States Army lawyer and jurist. During the Civil War, he served in the Union army and later became Judge Advocate General of the United States Army. Influence In 2015, the United States Department of Defense published its Law of War Manual. Francis Lieber is cited after Hugo Grotius and Emer de Vattel and before Hersch Lauterpacht as a subsidiary means and an authority in determining the rules of law of war. Works Encyclopaedia Americana (Editor, 1829–1851) The Stranger in America (2 vols., 1833–35) Letters to a Gentleman in Germany, written after a Trip from Philadelphia to Niagara (1834) A Manual of Political Ethics (2 vols. 8vo, Boston, 1838), adopted by Harvard College as a text book, and commended by Kent and Story Legal and Political Hermeneutics, or Principles of Interpretation and Construction in Law and Politics (1838) Laws of Property: Essays on Property and Labor (18mo, New York, 1842) The West and Other Poems (1848) (2