Notions of ‘Christendom’ often miss the mark – medieval Europe’s ideas about faith and power weren’t so easy

During the National Prayer Breakfast on Feb. 5, 2026, Paula White-Cain, senior adviser to the White House Office of Faith, introduced President Donald Trump as “the best champion of religion that we now have ever had in the manager branch.” Taking the rostrum after her, Trump declared, “I’ve done more for religion than some other president.”

Should an earthly leader be promoting a heavenly cause? Some of the Americans who say “yes” – in no way all – are likely sympathetic to the ideas and values of Christian nationalism. A blanket term, Christian nationalism ranges in meaning. Some residents might see themselves as Christian nationalists just because they’re Christian and patriotic. Others, nonetheless, assert that the United States is rightfully a Christian nation that should be governed by Christian leaders, ethics and laws.

As a historian, I’m aware that Christian nationalism relies upon a selective and infrequently distorted view of American history. As a historian of the European Middle Ages, specifically, I’m thinking about one other myth of a shared Christian past that seems to lie beneath the surface of some Christian nationalist claims. That’s the thought of the medieval Christian West, also generally known as “Christendom”: a time before the trendy separation of church and state.

1,000 years

What was Christendom? Similar to Christian nationalism, the term can mean various things to different people.

It generally recalls an extended time period – 1,000 years, give or take – between the “fall” of Rome around 500 C.E. and the start of the trendy era around 1500. Christianity dominated European politics, society and culture. The Middle Ages really were an era when kings ruled in Christ’s name, when the popes of Rome commanded obedience from believers around Europe, and when monasteries played an important role within the shaping of values and education.

In recent years, though, I’ve observed puzzling and ahistorical ways in which the concept of Christendom has began to seem in certain corners of conservative political thought. That era of Christian dominion is typically remembered as a lost age of Christian unity, a time when religion and politics were “properly” aligned.

Such views don’t map neatly onto any partisan position or religious affiliation. The Catholic-inspired website The Josias, for instance, a guide “for many who want to bring their faith into the general public square and resist the tides of liberalism, modernism, and ignorance of tradition,” is full of works by medieval thinkers.

In some conservative Protestant circles, one finds yearnings for the creation of a “recent Christendom,” an “American Christendom,” or, as pastor Doug Wilson calls it, “mere Christendom.”

Wilson is the founding father of the Communion of Reformed Evangelical Churches – one in every of which Defense Secretary Pete Hegseth attends. Wilson says that his vision of “mere” Christendom doesn’t entail a return to theocracy but “a network of countries sure together by a proper, public, civic acknowledgment of the Lordship of Jesus Christ, and the elemental truth of the Apostles’ Creed.”

In his 2023 book “The Boniface Option,” minister Andrew Isker calls for Christians to fight for the creation of “recent Christendom.” He also co-authored 2022’s “Christian Nationalism: A Biblical Guide for Taking Dominion and Disciplining Nations.”

From a historical perspective, there are many problems with such views of Christendom. For starters, they erase the truth that, while Christian authorities governed Christian-majority kingdoms throughout the Middle Ages, Europe was also home to Jewish and Muslims communities. They also paper over the proven fact that medieval Christians themselves never reached a consensus over the correct relationship between worldly and spiritual powers – or, as we’d call them today, church and state.

Faith and empire

When I teach on religion and politics, I compare two late ancient thinkers whose works left profound legacies on the medieval world: the primary historian of the church, Eusebius of Caesarea; and the immensely influential theologian, Saint Augustine.

Writing within the fourth century, Eusebius celebrated the reign of the primary Christian Roman emperor, Constantine, who ruled from 306-337. The story of Constantine’s conversion is known. As Eusebius told it, the emperor was marching toward Rome during a civil war when he saw a radiant “cross-shaped” vision within the sky, accompanied by the words “by this conquer.” That night, the “Christ of God” appeared to the emperor in a dream and told him to march to war under that sign, which he did with victory.

From Eusebius’ perspective, there was lots to have fun about Constantine’s reign. Constantine ended the persecution of Christians unleashed by his predecessors. Under his direction, imperial money flooded into clerical hands, followed by a wave of church constructing across the empire. The emperor granted bishops legal privileges and tax exemptions, and he called church councils to resolve disputes over Christian doctrine and organization.

In Eusebius’ eyes, this was all a part of the divine plan. As he wrote, God had intended for the reason that starting for the “two shoots” of the “empire” and the “gospel of Christ” to intertwine, grafted together in harmony. Pagan Rome, Eusebius claimed, had subdued the peoples of the world. Under Constantine, its rule was bringing the “excellent news” of Christianity to all those conquered nations.

This form of boosterism for Christian monarchs, hailed as “champions of the religion,” would endure throughout the Middle Ages and beyond. The Byzantine Empire, the Carolingian Empire, the Holy Roman Empire, Christian kingdoms from England to Armenia: Supporters saw their worldly power as representing the heavenly power of Christ, the “King of kings.” This was, in effect, a form of Christian nationalism before the rise of contemporary nations.

‘Not of this world’

Yet medieval Christian thinkers also maintained skepticism concerning the ability of temporal princes to appreciate God’s kingdom here on Earth.

This is where Augustine, who wrote “The City of God” within the early fifth century, comes into the image. Augustine was a prolific author and immensely complicated thinker whose views modified across the course of his lifetime. Similar to Eusebius, he believed that God determined the fate of all empires and kingdoms, whether Christian or not.

Augustine supported the appropriate of rulers to wage “just wars” and use force to take care of public order. Still, the bishop of Hippo hit the brakes on unbridled enthusiasm for the divinely appointed role of earthly empires and kingdoms, even when their rulers were Christian.

Living through the aftermath of Rome’s plundering in 410 by the Visigoths, Augustine keenly appreciated the proven fact that empires come and go. True happiness for Christian princes didn’t come from in search of their very own personal ends: winning battles, gaining essentially the most territory, leaving their thrones to their heirs, and conquering their enemies. It got here from putting their “power on the service of God’s mercy” and the greater good. “Remove justice,” Augustine asked in “The City of God,” “and what are kingdoms but gangs of criminals on a big scale?”

In Augustine’s view, which profoundly influenced medieval theologians and political thinkers, this world was the transitory “City of Man,” full of love of self and lust for domination. What really mattered was the everlasting “City of God.” There was nothing fallacious with Christian kingdoms, empires and nations, he thought, but there was nothing especially blessed about them, either. After all, hadn’t Jesus said within the Gospels, “My kingdom isn’t of this world”?

There has never been a singular Christian perspective on the connection between faith, power and political identities. There actually wasn’t on the planet of medieval Christendom. To suggest otherwise is a fantasy that misrepresents the sophistication of Christian political thought throughout the Middle Ages – and in the current.