On 10 FEB 1941, the Defense Act (H.B. No. 45) authorized a volunteer militia. Volunteers from the Plains and High Plains area were constituted as the 39th Battalion of the Texas Defense Guard. Volunteers from far West Texas were constituted as the 34th Battalion. These units remained active throughout World War II and in 1943 the 48th Legislature changed the name of the Defense Guard to Texas State Guard.

After the Texas State Guard was inactivated on 28 AUG 1947 (AGTX-GO 21), the 50th Legislature re-authorized the Texas State Guard Reserve Corps on 26 JAN 1948 (AGTX-GO 4) and the unit reformed and designated the 1st Regiment. In 1958 the unit was re-designated the 5th Military Defense Group and in 1965 renamed the 5th Military Police Group.

When the Texas State Guard reorganized on 1 JUL 1993 the state defense force from West Texas was designated as the 39th Brigade and the name Roughnecks reclaimed for the unit. On 10 Nov 1994 the far West Texas battalions were reorganized into the 9th Brigade but this unit was re-incorporated into the 39th Brigade on 20 May 1999.