William M. Davis, who was appointed Inspector General in February, 2006, served with the U.S. Army's 173rd Airborne Brigade in Viet Nam. After returning state-side, he began a 26 year career with the Illinois State Police, from which he retired as a Lieutenant Colonel. IG Davis, to date the longest serving Inspector General for this agency, was Inspector General from February 21, 2006 through July 31, 2012.