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;
Field officer Field officer A field officer, field-grade officer, or senior officer is an army, Marine, or air force commissioned officer senior in rank to a company officer but junior to a general officer. In most armies this corresponds to the ranks of major, lieutenant colonel and colonel, or their equivalents. Some countries also include brigadier in the definition. Historically, a regiment or battalion's field officers made up its command element. In the Canadian Armed Forces, the equivalent of field officers are senior officers (); they include the army and air force ranks of Major, Lieutenant-Colonel, and Colonel, and the naval ranks