7 The First World War involved many countries all over the world and caused grievous losses to many individuals and nations. When it finally ended, Benedict XV's Apostolic Letter (l4) (which We mentioned above), like the exalted invitation of a fatherly voice, enflamed the souls of all Catholics to expand peacefully the Kingdom of God, the only one, We say, which can give and secure permanent peace and prosperity to all men, children of their Heavenly Father. From that time, during forty very active years, the works and undertakings of the heralds of the Gospel have been flourishing and producing increasingly abundant fruits every day; and the most noteworthy result is the fact that a local hierarchy and clergy have been increasingly developed in the mission areas.
Source: Princeps Pastorum (Vatican.va)