The Rhodesian Defence Regiment was a unit of the Rhodesian Army formed on 1 January 1978 from existing units known as Reserve Holding Units and Protection Units. The Reserve Holding Units (for support roles) and Protection Units (for escorting supplies in combat zones) contained Rhodesia's coloured (i.e. mixed race) and Asian personnel, including both conscripts & volunteers.
From its formation, the regiment was also used to mobilise white reservists over the age of 38.
References
Rhodesian Defence Regiment Wikipedia(Text) CC BY-SA