19 September 1974
The South African Prime Minister, B.J. Vorster wished the new Mozambique government well. Voster however, warned that South Africa will have to act in self-defence if Mozambique makes its territory available to guerrilla forces as a base for attacks. This came after a coup in Portugal in 1974 forced the Portuguese to leave Mozambique. The new government, led by Samora Machel, took over on June 25, 1975. Machel became independent Mozambique's first President until his death on 20 October 1986. In 1981, 13 exiled members of the African National Congress (ANC) were killed in Matola, Mozambique.This was the first open act of war by the apartheid government against Mozambique. Three years later (March 1984), the Nkomati Accord, was signed. In this agreement both countries resolved not to harbour hostile forces or allow their countries to be used as launching pads for attacks on one another. Mozambique agreed to expel the ANC from their country while South Africa agreed to cease its support of RENAMO, an anti-government guerrilla organisation in Mozambique.      
References

O’Malley P. ‘1974’, from Nelson Mandela Centre of Memory and Dialog, [online], Available at www.nelsonmandela.org [Accessed: 18 September 2013)|Blue Footprints, History and Politics Mozambique, [online], Available at www.bluefootprints.com [Accessed: 18 September 2013]