Why has Pope Francis declared October an Extraordinary Month of Mission? One reason is that he wanted to mark the 100th anniversary of an apostolic letter that guided the Church’s missionary work throughout the 20th century. Maximum illud was certainly an influential text. Like many Vatican documents, it took its name from its opening words, in which Pope Benedict XV recalled “that momentous and holy charge” in St Mark’s Gospel: “Go into the whole world and preach the Gospel to all creation.” But this month is not only about commemorating a far-sighted letter that distanced the Church from colonial powers in missionary lands. It is also about giving new momentum to Catholic missions around the world.