26 "Suppose owing to war or political upheavals there is a change of government in some missionary territory, and the request is made or a law is passed that the foreign missionaries of a certain country must leave: suppose again a more unlikely case, that the native population raised to a higher degree of culture and political development, in order to attain its freedom, wants to drive out of their territory all governors, armed forces and missionaries belonging to the occupying foreign power and that it cannot do so otherwise than by force. What then, We ask, would be the disaster that would threaten the Church throughout all that territory, unless full provision has been made for the needs of the Christian populace by a network of native priests throughout the whole country?"
Source: Evangelii Praecones (Vatican.va)