I just found Quod Iam Diu on your website, CM.  This is about a peace conference to follow the first World War.  You take excerpts from the second paragraph but I will print the whole paragraph.

Quod Iam Diu, Benedict XV:

"Words, then, are not required to show how great need they have of being illuminated from on high that they may carry out their great task well. And, as their decisions will be of supreme interest to all humanity, there is no doubt that Catholics, for whom the support of order and civil progress is a duty of conscience, must invoke Divine assistance for all who take part in the peace conference. We desire that that duty be brought before all Catholics. Therefore, Venerable Brothers, in order that there may come from the Congress shortly to be held that great gift of heaven, true peace founded on the Christian principles of justice, that enlightenment from the Heavenly father may descend on them, it shall be your care to order public prayers in each parish of your dioceses in the way you may think most convenient. As for Us, representing, however unworthily, Jesus Christ, King of Peace, We shall exert all the influence of Our Apostolic Ministry that the decisions which are to be taken to ensure for ever in the world [ !!!!!! ] the tranquility of order and concord be willingly accepted and faithfully carried out by Catholics everywhere."

CM says that simply to hope for peace to be brought to the world through other means than the Catholic religion is heresy, and quotes Pius X.  Apparently he thinks that Benedict XV was talking about the League of Nations, but, from Wikipedia --

"Benedict rejected the League of Nations as a secular organisation that was not built on Christian values."

So Quod Iam Diu is calling for a peace conference to end the war, but we cannot read into it that it gave implicit support to the League of Nations.  Both sides in the war had Catholics on them, although one side ultimately was really fighting for ʝʊdɛօ-Masonry -- the Allies.  

Therefore, it can't be said that he is calling for a non-Catholic peace in those strict terms.  It was more like a peace of deceived Catholics that he invoked, since the end of World War I marked a victory of ʝʊdɛօ-Masonry.  Benedict XV used the phrase "Christian justice" instead of Catholic justice, as if to rub this in.  

The underlined and bolded words and sentences in the encyclical sound Masonic, and it's very likely his sympathies were against the Church.  But did he teach heresy?  I still haven't seen it.  Just the fact that he didn't explain how Fɾҽҽmαsσɳɾყ triggered the war, though, is suspicious -- and Pius X also falls under that suspicion.  Since the fortunes of the papacy and of the Church really relied on Austria winning this war, how come the Popes didn't throw their full weight behind their cause?  Was it peer pressure since Italy was on the side of the Allies?

Man oh man, can the devil weave a tangled web.