The Boer War started when Britain annexed parts of South Africa held by Dutch farmers in 1877. The region, called the South African Republic, or the Transvaal Republic, revolted in 1880.
Boer is the Dutch and Afrikaans word for farmer. The British wanted to form and rule a confederation of South African states. When they annexed the Transvaal Republic, it was having financial problems. This made the British believe that annexation would be accepted because people were dissatisfied by the government.
The 1879 Zulu-Anglo War depleted British forces and made war seem more feasible to the Boers. The war started when a Boer man refused to pay extra taxes on his wagon and the British confiscated the wagon. A group of about 100 men took back the wagon by force, and around 9,000 Boers gathered to protest British rule.