In the summer of 1914, when Europe went to war, its churches declared holy crusades. Over the next four years the horrors of trench warfare, gas attacks and suicidal marches into machine-gun fire destroyed the credibility of the churches that had promised battlefield glory for God and country. One hundred years later, World War I stands as a warning against enlisting religious faith in the service of armed violence.

Several countries saw the war as a fulfillment of their unique and righteous destinies, writes Philip Jenkins in The Great and Holy War: How World War I Became a Religious Crusade (HarperOne, 2014). The language of holy war poured from Germany’s pulpits. “Come, Sword, you are to me the revelation of the Spirit,” declared a Lutheran pastor, Franz Koehler.

U.S. Christians who at first wanted no part of the Old World’s carnage quickly fell in line when their own nation issued a call to arms. “Across the religious spectrum, most Christians (and Jews) expressed clear antiwar views when the European conflict broke out in 1914,” Jenkins writes. Even late in 1916 churches still spoke out against war. But by the time the U.S. entered the war in April 1917, “American clergy yielded nothing to their foreign counterparts in their willingness to transform the cross into the bayonet. . . . Some of the most militant voices were penitent former pacifists.”

And what of those who persisted in pacifism? The war brought persecution, particularly in the Midwest, where Mennonite immigrants who still spoke German, the language of the enemy, became targets of hatred and violence. Suspected or proven arson fires destroyed Mennonite churches in Fair­view, Mich., and Inola, Okla., and the main building at Tabor College in Hillsboro, Kan. Mobs terrorized Mennonites who refused to buy war bonds, nearly lynching their victims in Kansas and Montana.

Pacifist conscripts reported to military camps and hoped for the best. Many suffered physical abuse, especially those who refused to wear the uniform or follow orders. “You can’t imagine how it is to be hated,” wrote David Koehn and William Frantz from Camp Greenleaf in Georgia. “If it wasn’t for Christ, it would be impossible.” Two Hutterite brothers, Joseph and Michael Hofer, died at Fort Leavenworth in Kansas after enduring abuse and torture. Duane C.S. Stoltzfus tells their story in Pacifists in Chains: The Persecution of Hutterites During the Great War (Johns Hopkins, 2013). The army clothed Joseph Hofer’s dead body in the military uniform he had refused to wear.

“Against considerable odds,” writes Gerlof D. Homan in American Mennonites and the Great War (Herald, 1994), “most Mennonite draftees remained faithful to nonresistance.” About 10 percent accepted regular military service rather than noncombatant roles. Overall, Homan concludes, the war strengthened Mennonite pacifism. It also gave U.S. Mennonites “living examples of Christian heroism in the face of persecution,” James C. Juhnke writes in A People of Two Kingdoms (Faith and Life, 1975). One could hardly have expected them to “challenge the myth of the Great American Crusade,” he says, because they lacked “the political sophistication to challenge the assumptions of the warmaking country.” Are we wiser now?