Black Zimbabweans had been fighting for their rights for many decades. Opposition parties formed, such as the Zimbabwe African Peoples Union (ZAPU) under Joshua Nkomo. In 1963, this party split and the more radical wing formed the Zimbabwe African National Union (ZANU). Guerrilla warfare broke out, turning into civil war in the 1970s.
The Lancaster House Agreement ended biracial rule in Zimbabwe Rhodesia following negotiations between representatives of the Patriotic Front (PF), consisting of ZAPU (Zimbabwe African Peoples Union) and ZANU (Zimbabwe African National Union) and the Zimbabwe Rhodesia government, represented at that time by Bishop Abel Muzorewa and Ian Smith. It was signed on 21 December 1979.
In the early 1970s, informal attempts at settlement were renewed between the United Kingdom and the Rhodesian administration. Following the April 1974 coup in Portugal and the resulting shifts of power in Mozambique and Angola, pressure on the Smith regime to negotiate a peaceful settlement increased. In addition, sporadic antigovernment guerilla activity, which began in the late 1960s, increased dramatically after 1972, causing destruction, economic dislocation, casualties, and a slump in white morale. In 1974, the major African nationalists groups--the Zimbabwe African Peoples Union (ZAPU) and the Zimbabwe African National Union (ZANU), which split away from ZAPU in 1963--were united into the "Patriotic Front" and combined their military forces, at least nominally.