In 1914, today was a day of peace in Europe before war began--it was a Thursday--and the next day, the Austro-Hungarian Empire declared war on Serbia. On Saturday, July 29, Austria started bombing Belgrade, and Russia mobilized against Austria. The day after that, Austria and Russia started mobilizing against each other. On July 31, Germany issued an ultimatum to Russia and another one to France--step by step, day by day, the great powers of Europe moved closer and closer to waging war against one another.
The video above, from the Catholic News Services, emphasizes the efforts of Pope Benedict XV, elected in September of 1914 after the death of Pope Pius X, to negotiate peace at the beginning of the war--a Christmas truce in 1914--and a just peace at the end of the war. He was consistently ignored, as this EWTN page notes:
In his November 1, 1914 encyclical Ad Beatissimi Apostolorum (Appealing for Peace), he reached out to the Patriarchs, Primates, Archbishops, Bishops, and Other Local Ordinaries in Peace and Communion with the Apostolic See to remind themselves and their communities of their Christian brotherhood:
He discussed the various evils of the day (besides the war) and how they contributed to the unrest that led to the war, including atheism, greed, racial hatred, contempt of laws and authority, etc. He urges the bishops and the patriarchs and bishops to be unified, charitable to each other, and to pray: