Hays Parks is widely regarded as the preeminent authority in the United States on the Law of War (jus in bello). He has held the prestigious Charles H. Stockton Chair of International Law at the Naval War College, been a Professor of International Law at the Army JAG School, and been an adjunct professor at American University School of Law, George Washington National Law Center, and numerous military war colleges. A combat Marine veteran of the Vietnam War (and retired Marine Reserve Colonel), between 1977 and 1979 he served as Head of the Law of War Branch, International Law Division, Office of the Judge Advocate General of the Navy. He then served for twenty-four years as Special Assistant to the Judge Advocate General of the Army for Law of War Matters, before in 2003 becoming Senior Associate Deputy General Counsel, International Affairs Division, Office of General Counsel, Department of Defense—where he also served as Chairman of the DoD Law of War Working Group and is the principal author and editor-in-chief of the not yet released Department of Defense Law of War Manual. Professor Parks has also served as a member of the U.S. delegations (usually as the senior Defense Department representative and often as chairman of the U.S. delegation) to more than forty international conferences and meetings of experts on a wide range of jus in bello issues over the decades. He has received numerous awards and honors for his professional writing (including the top writing awards from the Army JAG School, Air University Review, the U.S. Naval Institute, and the Navy League), the Department of State Superior Honor Award, and the Secretary of Defense Medal for Exceptional Civilian Service.