 On the same day, a tripartite agreement between Angola, Cuba and South Africa was signed, whereby South Africa agreed to hand control of Namibia to the United Nations.UN Security Council adopted resolution 632 on 16 February 1989 requiring that implementation of UNSCR 435 should officially start on 1 April 1989.AG Pienaar, under the supervision of UN Special Representative Martti Ahtisaari who arrived in Windhoek in April 1989 to head the United Nations Transition Assistance Group, began Namibia's transition to independence.