Earlier this month, the Leonine Walls reappeared in commentary about the current conflict with Iran — cited as evidence that the papacy has always understood the Muslim world as a threat, and that the Pope's refusal to align with either side in the Iran war amounts to a kind of historical betrayal. The argument is neat. It is also about nine centuries too short.
Pope Leo IV ordered the construction of those walls in 848 AD, in the years after a Saracen raid on St Peter's Basilica. That raid was real. The threat was real. But the walls built in its aftermath went on to face Lombard princes, Holy Roman Emperors, French armies, mercenary bands hired by rival Italian factions, and — most humiliatingly — the forces of a Catholic king. In 1527, Charles V's troops sacked Rome. The destruction was vast. The perpetrators were, by confession, Christian.
What the walls actually record is something far less legible than the story currently being told about them: the Vatican has spent the better part of two millennia navigating enemies of every faith, ideology, and allegiance. The institution's survival has depended less on religious solidarity than on the kind of political calculation that makes modern commentators deeply uncomfortable.
Eamon Duffy's Saints and Sinners, the most authoritative single-volume history of the papacy, traces this with clarity — an institution that allied with Frankish warlords, excommunicated Holy Roman Emperors, and financed military campaigns that had as much to do with territorial ambition as theological conviction. The popes who built walls were the same popes who negotiated treaties with the powers those walls were built against.
The medieval encounter between Christian and Muslim worlds was, in any case, nothing like the binary it has become in contemporary usage. Thomas Asbridge's The Crusades is one of the few popular histories to approach this seriously — reconstructing the conflict from both sides, and finding in the process that the boundaries between cooperation and warfare were consistently blurred. Saladin released prisoners. Crusader lords maintained treaties with Muslim neighbours when it suited them. The lines drawn on modern maps of grievance rarely correspond to those that existed on the ground in 1099, or 1187, or 1291.
Jonathan Phillips' Holy Warriors goes further, tracing the long afterlife of the crusading idea — how it was romanticised, politicised, and repeatedly reinvented from the twelfth century to the twentieth. The word "crusade" entered modern political language through nineteenth-century romanticism, not medieval theology. When it surfaces today, it carries that accumulated distortion with it.
The Leonine Walls still stand. But the history encoded in them is not a simple argument about civilisational allegiance. It is a record of an institution that survived by being more complicated than any single reading of it allows.
Further Reading
Saints and Sinners: A History of the Popes — Eamon Duffy. The standard account of the papacy from its origins to the present day; rigorous on the institution's political entanglements as well as its spiritual ones.
The Crusades — Thomas Asbridge. A dual-perspective history of the medieval conflict for the Holy Land, tracing the logic of both crusade and jihad without flattening either.
Holy Warriors — Jonathan Phillips. Traces the crusading idea from Pope Urban II to the modern era, and examines how a medieval concept was repeatedly rewritten for political purposes.