20 This situation has come about from a number of causes, which are in general the outcome of rather recent historical events, and it has further been influenced to some extent by the conduct of certain nations that glory in the fact that the light of Christianity illuminates their annals. There is every reason, therefore, why We should be subject to no small anxiety with regard to the fortunes of Catholicism in Africa. There is every reason too why all the Church's children should clearly realize their serious obligation to give more effective assistance to the missionaries. This they must do at the opportune moment in order that the message of saving truth may be brought to what is called "darkest" Africa, where some 85,000,000 people still sit in the darkness of idolatry.
Source: Fidei Donum (Vatican.va)