It is impractical for the governor of Texas to operate the military themselves, so their command authority is delegated via commission to the adjutant general.

The department was abolished from February 4, 1856 to April 6, 1860 due a fire on October 10, 1855 that destroyed nearly all records.

The department was again abolished from January 1, 1867 to June 24, 1870 in the aftermath of Texas's failed attempt at seceding from the United States.

During World War I, the Department of Texas was re-designated the Adjutant General Department and again maintained provincial "Home Guard" forces for defense of the state while the Texas National Guard was under federal command.

OAG is the principal staff element of the Adjutant General in the exercise of policy development, planning, resource management, fiscal and program evaluation and oversight, and interface and exchange with other Texas Government departments and agencies, foreign governments, and international organizations, through formal and informal processes.