This essay focuses on the political and religious action of one of the most influential princes of the Church during the First World War. Regarded as a patriot and leading figure of the liberal ecclesiastical area, the Cardinal-Archbishop of Pisa Pietro Maffi kept a low profile during the period of Italian neutrality, praying for peace and telling the faithful to stay calm. Italy's declaration of war on the Austro-Hungarian Empire brought drastic change: Maffi became the symbol of the union between faith and patriotism, repeatedly stating that the Italian cause was not only just but also sacred. After the defeat of Caporetto, he advocated resistance at all costs and stressed the bond between religion and the nation, turning the war into a crusade. The case of Maffi shows the complexity of the Catholic attitude towards the conflict, seen both as the result of the apostasy of the modern world and as a vital opportunity to rebuild the Christian society destroyed by the principles of 1789.