Sigrid Undset said this quote
“ It seems to her [Saint Catherine of Siena] that the devil has this world in his power, not by his own will, for he is powerless, but through our help because we obey him. The evil aroma rising from the ... wars which are waged by Christians against Christians, are the same as war against God. ... Peace, peace, for the sake of the love of the crucified Christ, and not war; that is the only solution. ”