The song was first adopted by the Viet Cong forces when they proclaimed a provisional government in 1969 in the areas they controlled. After the fall of the capital Saigon to the Communist Viet Cong forces, “Release the South” became the anthem of South Vietnam until the unification of Vietnam was completed one year later. The anthem was written by the same person who wrote the anthem of the previous democratic South Vietnam government, only this work was written after he became a Communist.
Special thanks to: Wilson Lin for some of this information.