Pope Paul VI
Mense Maio §10
Mense Maio: On Prayers During May for Preservation of Peace
10 But peace, Venerable Brothers, is not solely the work of man. It is also, and primarily, a gift from God. Peace comes from heaven. It will truly reign among men when we have finally proved ourselves worthy to receive this gift from Almighty God. Just as the happiness and destiny of nations are in His power, so also are the hearts of men. And so we shall obtain this lofty benefit by praying to God; by praying with constancy and watchfulness, as the Church has been wont to do from her very beginning; by praying, in particular, for the intercession and protection of the Blessed Virgin Mary, who is the Queen of peace.
Source: Mense Maio (Vatican.va)