In addition to establishing the free burgher system, van Riebeeck and the VOC began to make indentured servants out of the Khoikhoi and the San. They additionally began to import large numbers of slaves, primarily from Madagascar and Indonesia. These slaves often married Dutch settlers, and their descendants became known as the Cape Coloureds and the Cape Malays. A significant number of the offspring from the White and slave unions were absorbed into the local proto-Afrikaans speaking White population. With this additional labour, the areas occupied by the VOC expanded further to the north and east, with inevitable clashes with the Khoikhoi. The newcomers drove the beleaguered Khoikhoi from their traditional lands and destroyed them with superior weapons when they fought back, which they did in a number of major wars and with guerrilla resistance movements which continued into the 19th century. Europeans also brought diseases which had devastating effects against people whose immune system was not adapted to them. Most survivors were left with no option but to work for the Europeans in an exploitative arrangement that differed little from slavery. Over time, the Khoisan, their European overseers, and the imported slaves mixed, with the offspring of these unions forming the basis for today's Coloured population.