He was President of the South African Republic (1857–71), having followed his father, Andries Pretorius, in the Great Trek. After fighting the Zulu, he became one of the four Transvaal commandant-generals, and was elected President. He was also elected President of the Orange Free State (1859–63). His claim to diamond fields (1867) on the Vaal River brought him into conflict with British interests. Following the annexation of the Transvaal by Britain in 1877 he was imprisoned. With the outbreak of the First Boer War (1880–81) he proclaimed with Kruger and Joubert a new Boer republic (January 1881). After the victory of Majuba Hill, he was a signatory of the Treaty of Pretoria, which re-established the independent states of Transvaal and Orange Free State.