12 As a matter of fact, there have never been lacking, either in ancient or in more recent times, those who tried to subjugate the peoples by the use of arms; on the other hand, We have never ceased to promote a true peace. The Church desires to win over peoples and to educate them to virtue and right social living, not by means of arms but with the truth. For "the weapons of our warfare are not carnal, but mighty to God" (II Cor . 10, 4).
Source: Summi Maeroris (Vatican.va)