The two major Bantu political groupings in West Central Africa centre on the Kongo kingdom and on the Luba-Lunda states. To the south of Kongo and east of Lunda live the Mbundu people who, from the end of the fifteenth century, developed contacts with the Portuguese and eventually became the main link between Western Bantu Africa and Europe. During most of the sixteenth century this relationship was based on trade in slaves. The benefits of this trade enabled the Mbundu to consolidate the small state of Ndongo, on the north side of the Kwanza River, into a moderately powerful kingdom. In the mid-sixteenth century Ndongo prosperity caused a migrant Lunda group called the Imbangala, who had camped on the eastern border of Mbundu country, to attack the Mbundu and make direct contact with the Portuguese. From 1575 the Portuguese embarked on a programme of territorial conquest. This continued through most of the seventeenth century, the great period of the Angolan Wars. The Portuguese suffered many setbacks, the lowest ebb being from 1641 to 1648 when the Dutch temporarily captured and held Luanda. By 1671, however, the independent Mbundu monarch in Ndongo had been eradicated. Thereafter the main African trading states of the area were Matamba and Kasanje on the Kwango River. After the wars the Luanda slave trade declined, North European competition from Loango and Portuguese competition from Benguela caused a serious depression in Mbundu trade during most of the eighteenth century. Only after 1790 were there signs of a revival