Did wars such as the Anglo-Zulu War, the Boer War, and the First Matabele War cause the British to decolonize?
These wars, while bloody, did not lead to decolonization, in fact they strengthened the grip of the British Empire on African territories. The Zulu War (1879), which was sparked by British attempts to consolidate their control of South Africa, led to the fragmentation of a formerly consolidated Zulu people into multiple chiefdoms, a situation which weakened their ability to resist British rule. Similarly, the Matabele War (1893) led to the destruction of the Matabele nation by the Royal South African Company, giving the British control over most of what is now Zimbabwe.
While the Zulu and Matabele Wars were fought in an effort to subjugate native African peoples, the Boer Wars, (1899-1902) were fought against the Afrikaners, who were white descendants of Dutch settlers. The British crushed Boer resistance, bringing the Transvaal under their control. Each of these wars involved immense loss of life, especially among African people, but they did not lead to decolonization, which would not take place until after World War II. Rather they strengthened the British presence on the African continent and convinced many British imperialists that they were inherently superior to colonial peoples, who they could rightfully exploit.