The Portuguese and Spanish became great colonizing nations at the end of the Middle Ages. Portuguese colonization, which received impetus from the development of greatly improved methods of navigation, began with the establishment of trading ports in Africa and the East, while the Spanish concentrated most of their efforts in the Americas. Both the Spanish and the Portuguese exercised strict governmental control over their colonies and used them primarily as a basis for rich commerce with the parent government. They discouraged them from becoming economically self-sufficient.