Historians usually note the upsurge of religious enthusiasm that greeted the outbreak of war. German preachers, for instance, debated whether they should see the national mood in terms of Transfiguration or of a New Pentecost. All the main combatants deployed Holy War language, particularly the monarchies with long traditions of state establishment — the Russians, Germans, British, Austro-Hungarians, and Ottoman Turks — but also those notionally secular republics: France, Italy, and (later) the United States. What we may miss, though, is just how persistent and overwhelmingly widespread such language was, and how it was reflected in the enormous outpouring of visual imagery.
More specifically, with the obvious exception of the Turks, it was a Christian war. With startling literalism, visual representations in all the main participant nations placed Christ himself on the battle lines, whether in films, posters, or postcards. Jesus blessed German soldiers going into battle; Jesus comforted the dying victims of German atrocities; Jesus personally led a reluctant Kaiser to confront the consequences of his evil policies. Apart from the obvious spiritual figures — Christ and the Virgin — most combatant nations used an iconography in which their cause was portrayed by that old Crusader icon Saint George, and their enemies as the Dragon. Death in such a righteous cosmic war was a form of sacrifice or martyrdom, elevating the dead soldier to saintly status.
In every country, mainstream media stories offered a constant diet of vision and miracle, angels and apocalypse. Angels supposedly intervened to save beleaguered British troops, the Virgin herself appeared to Russians, while Germany claimed to follow the Archangel Michael. Those stories circulated in the first days of the war, and they persisted through the whole struggle, long after we might expect the armies to be wholly focused on the grim realities of front-line life. When the Germans launched their last great offensive in 1918, of course it was called Operation Michael. For the Allies, religious and apocalyptic hopes crested in 1917 and 1918, with the great symbolic victories in the Middle East. Most evocative were the capture of Jerusalem from the Turks, and the decisive British victory at — honestly — Megiddo, the site of Armageddon.
My colleague Philip Jenkins, on his new book The Great and Holy War: How World War I Became a Religious Crusade