The Atlantic slave trade peaked in the late 18th century when the largest number of slaves were captured on raiding expeditions into the interior of West Africa. These expeditions were typically carried out by African states, such as the Bono State, Oyo empire (Yoruba), Kong Empire, Kingdom of Benin, Imamate of Futa Jallon, Imamate of Futa Toro, Kingdom of Koya, Kingdom of Khasso, Kingdom of Kaabu, Fante Confederacy, Ashanti Confederacy, Aro Confederacy and the kingdom of Dahomey. Europeans rarely entered the interior of Africa, due to fear of disease and moreover fierce African resistance. The slaves were brought to coastal outposts where they were traded for goods. The people captured on these expeditions were shipped by European traders to the colonies of the New World. As a result of the War of the Spanish Succession, the United Kingdom obtained the monopoly ("asiento de negros") of transporting captive Africans to Spanish America. It is estimated that over the centuries, twelve to twenty million people were shipped as slaves from Africa by European traders, of whom some 15 percent died during the terrible voyage, many during the arduous journey through the Middle Passage. The great majority were shipped to the Americas, but some also went to Europe and Southern Africa.