How do you know?
The Pope tried to stop World War One during the fighting, but does anyone remember? Popes have tried to stop many wars since then. They issue statements calling for peace.
But since, as Stalin observed, the Pope has no divisions, these papal statements are mocked or ignored. Or castigated for not taking one or the other side.
Plenty of “Catholics” in the Vatican were more than willing to help the Ustashe in Croatia during WWII.