Complex sentence: The Transvaal was colonised by Boer settlers who exited the British-dominated Cape Colony in the 1830s and 1840s in the Great Trek and established several republics outside British control-after the British occupation of the former Dutch colony in 1795 and again in 1806.
Split into simpler sentences: The Transvaal was colonised by Boer settlers who left the British-dominated Cape Colony in the 1830s and 1840s in what came to be known as the Great Trek. The emigrating Boers established several republics to the north, outside British control-after the British occupation of the former Dutch colony in 1795 and again in 1806.