The "Gukurahundi" ended with the signing of the Unity Accord on 22 December 1987. The accord, signed by Prime Minister Mugabe and ZAPU leader Joshua Nkomo merged ZANU and ZAPU into the Zimbabwe African National Union – Patriotic Front, or ZANU–PF. On 18 April 1988, Mugabe announced amnesty for all dissidents, and in return, Nkomo called on them to lay down their arms. In the late 1980s, a series of court cases exposed the existence of apartheid South African spies within the CIO, who played a significant role in causing the "Gukurahundi" by providing distorted intelligence reports and purposely inflaming ethnic tensions. These spies, white holdovers from the Rhodesian era, contributed to South Africa's interest in destabilizing Zimbabwe. In particular, they sought to damage ZAPU and ZIPRA, which maintained close ties to the African National Congress, the leading anti-apartheid group fighting the government in South Africa. Mnangagwa admitted that the South Africa had a "major implant in intelligence under Smith" and that "they initially left these implants." Asked why these agents were allowed to remain the CIO, he responded "We had no choice. We could not allow our whole intelligence capability to collapse overnight."