 Racist ideology thus helped legitimize the conquest and incorporation of foreign territories into an empire, which were regarded as a humanitarian obligation partially as a result of these racist beliefs.However, during the 19th century, Western European colonial powers were involved in the suppression of the Arab slave trade in Africa, as well as in the suppression of the slave trade in West Africa.Some Europeans during the time period objected to injustices that occurred in some colonies and lobbied on behalf of aboriginal peoples.