Kongo, which had been in contact with the Portuguese since 1482, held a monopoly on trade with this country. When a NDongo's leader, or "ngola", tried to break this monopoly, this led to war, in which the Bakongo were defeated in 1556. NDongo was now independent, and directly confronted Portugal's colonialism. It allied itself with Matamba against the country in 1590, but was defeated in 1614. Now, NDongo itself became a target for the slave trade, and its population fled in large numbers to neighbouring states.