The lineage of the 138th Regiment can be traced back to September 1942 when it was formed as the 638th Tank Destroyer Battalion. In 1951, it was re-designated as the 138th Tank Battalion, and in June 1960 re-designated as the 138th Armor Battalion. The 138th Armor Battalion was inactivated and the colors were cased in June 1967.
The Indiana Military Academy was established in 1956 as an Officer Candidate School at Indianapolis. In December 1965, the Indiana Military Academy was moved to Camp Atterbury. After moving to Camp Atterbury, the curriculum was expanded to include Non-commissioned Officer Education Courses and Military Occupational Specialty Qualification Courses.
In 1996, the Indiana Military Academy was reorganized as part of The Army School System and given the designation as the 138th Regiment (Combat Arms). Restructured with a Headquarters and General Studies Battalion, the 138th Regiment was responsible for Combat Arms Training within a region consisting of six states: Indiana, Illinois, Ohio, Michigan, Minnesota and Wisconsin.
Today, the 138th Regiment conducts Officer Candidate School, Warrant Officer Candidate School and Combat Arms Training for Soldiers not only from Indiana but throughout the Army National Guard and Army Reserve.
The distinctive unit insignia (DUI) for the 138th Regiment symbolizes the service of the former organization, the 138th Armor Battalion. It is depicted by the golden leopard springing upon its prey, indicating the unit’s ability to move swiftly and silently while stalking its prey, then striking at the opportune moment with all the power and force at its command. It is felt that the leopard represents the animal most typical of this type of attack-powerful, silent, and swift, who by means of cunning as well as great strength is the greatest of all hunters. The eye of the leopard is emerald green, symbolic of its ability to see and hunt in the dark. Thus, the motto associated with the 138th Regiment is “Seek and Destroy.”