This war signaled end of Zulu independence, and shouldn't be confused with the Boer Wars (1880-1881 and 1899-1904). It was a complicated transfer of land and succession to King Mpande of Zululand (1840-1872), Boers, the king's sons, and the Utrecht district (read the background here: http://en.wikipedia.org/wiki/Anglo-Zulu_War#Background).
The new king Cetshwayo kaMpande (1872-1879) refused British demands of outrageous reparations for a minor boarder schirmish. In January 1879, a British force under Lieutenant General Frederick Augustus Thesiger, 2nd Baron Chelmsford invaded Zululand. Apparently, even though they declared a state of war to exist when Cetshwayo refused their demands, there was no authorisation by the British Government
Confused? It’s way more complicated than this. But the bottom line is all about colonialism.