Ngoma is believed to have come to southern Africa during the western Bantu migration that began around 2000 BCE and was further influenced by the eastern Bantu migration that occurred until 500 CE. The practice has evolved along with the social problems of its users. In pre-colonial form ngoma songs dealt mainly with issues of hunting. Over time the system adapted to include the introduction of guns, and later the racial and class struggles of practitioners under colonial rule. In Zimbabwe, the civil war experience led to a revival of ngoma practice with a new emphasis on the spirits of the victims of war. The service allowed the sangoma to help people cope with their own violent acts as well as those they had fallen victim to. An example of this is the Tsonga who believe that one of the main alien spirits that can bestow powers of clairvoyance and the ability to detect witchcraft is the Ndau Spirit. The Ndau spirit possesses the descendants of the Gaza soldiers who had slain the Ndau and taken their wives. Once the Ndau spirit has been converted from hostile to benevolent forces, the spirits bestow the powers of divination and healing on the n'angna.