History of the Office of The Inspector General of the United States Army (IG January 10, 1863April 1, 1864; January 2, 1881March 8, 1885) was assigned as the "de facto" head of the Office of the Inspector General, which, until then had not existed. 2 major generals, 7 brigadier generals, 18 colonels, 118 lieutenant colonels, and 149 majors of the regular army served inspector duty during the Civil War. On January 22, 1866, a War Department order established the duties of the inspector general as: In July 1866, the number of inspectors general with the rank of colonel was fixed at four; assistant inspectors general with the rank of lieutenant colonel at three;
Lieutenant colonel (United States) 1791, there was only one lieutenant colonel in the US Army (Josiah Harmar), who acted as the army's commanding officer. In the Continental Army aides to the Commander in Chief, viz., Lieutenant General George Washington, were lieutenant colonels. Additionally, certain officers serving under the Adjutant General, Inspector General, and Judge Advocate General, ranked as lieutenant colonels. During the 19th century, lieutenant colonel was often a terminal rank for many officers, since the rank of "full colonel" was considered extremely prestigious reserved only for the most successful officers. Upon the outbreak of the Civil War, the rank of lieutenant colonel became