"Historiography has established though, that at least since the 18th century people in the Western part of the Bahr El Ghazal river system area were constantly on the move because of external pressures.Social groups were rather small and shifted frequently to avoid attacks from powerful neighbours who already possessed European weapons and forcefully expanded the trans-Saharan and Nilotic trading networks into the hinterlands for the exploitation of copper, ivory, ostrich feathers and slaves.