From Augustine to Chivalry: The Theological Foundations of Just War

The medieval period witnessed a paradoxical relationship between Christianity and warfare. While the faith preached peace, the 4th-century theologian Augustine of Hippo formulated the doctrine of bellum justum (just war), which became foundational for Christian rulers. According to this principle, war became permissible when waged to restore peace after unjust aggression – particularly when defending Christian lands against invaders or rebels. The biblical injunction from Matthew 5:9 (“Blessed are the peacemakers”) was reinterpreted to justify military action when peacemaking failed.

By the 11th century, these ideas had evolved into the chivalric code, establishing rules for honorable combat. Knights were expected to spare non-combatants – especially women, children, clergy, and the infirm – unless they aided enemies. This ethical framework drew heavily from Old Testament narratives like Joshua’s conquests, where divine intervention sanctioned warfare (Joshua 10:12). The New Testament’s apparent pacifism, exemplified by Jesus rebuking Peter in Gethsemane (Matthew 26:52), was reinterpreted to mean clergy shouldn’t bear arms personally but should spiritually oversee warfare.

The Two Swords and Sacred Violence

The “Two Swords Theory” became crucial in medieval Christian political thought. The spiritual sword (excommunication and sacramental control) belonged to the Church, while the temporal sword (physical force) rested with secular rulers. However, reformist clerics argued the Church should direct both, making warfare a sacred act when properly authorized.

Pre-battle rituals exemplified this fusion:
– Fasting and collective prayer
– Priestly blessings over armies
– Recitation of Psalm 20 (“Some trust in chariots… but we trust in the Lord”)
– Post-victory celebrations modeled on Joshua’s conquests

These practices created a religious framework for violence that would culminate in the Crusades.

Millennial Fervor and the Road to Clermont

The 11th century saw widespread apocalyptic expectations across Western Europe. Several factors fueled this atmosphere:
– Growing devotion to Jerusalem (evidenced by naming girls “Jerusalem”)
– Surge in pilgrimages (a 1054 group numbered 3,000; 7,000 Germans traveled in 1064-65)
– Reports of Muslim atrocities against Eastern Christians (like the 1086 Sagrajas battlefield desecration)

Pope Gregory VII (1073-85) first envisioned a holy army to rescue Eastern Christians, but the Investiture Controversy prevented action. His successor Urban II (1088-99) inherited both Gregory’s vision and a network of monastic-noble alliances forged through the Peace and Truce of God movements. These relationships, based on mutual prayer and protection, provided the social infrastructure for crusading.

The Fateful Sermon at Clermont

On November 27, 1095, Urban II’s sermon at Clermont ignited history’s most consequential call to arms. While the exact wording is lost, key elements emerged:
– Emphasis on aiding Eastern Christians
– Vague promises of spiritual rewards
– The crowd’s spontaneous cry: “Deus vult!” (God wills it!)

The Pope framed the expedition as:
– A just war against unjust aggression
– An alternative to damnable local warfare
– A penitential pilgrimage with arms

This novel fusion of pilgrimage and holy war created unprecedented enthusiasm, though practical concerns soon surfaced about costs, distance, and burial far from home.

The People’s Crusade: Zeal and Tragedy

Before the organized noble forces departed in August 1096, several popular crusades erupted with disastrous results:

### The Rhineland Pogroms
Count Emicho of Flonheim’s forces perpetrated horrific anti-Jewish violence across German cities:
– Massacres in Speyer, Worms, and Mainz
– Forced conversions in Regensburg
– Jewish communities responding with martyrdom, including parents killing children

These events profoundly impacted Jewish-Christian relations and inspired new Jewish pietist movements like the Hasidim.

### Military Disasters
– Walter Sansavoir’s and Peter the Hermit’s groups reached Constantinople but were destroyed in Anatolia
– Gottschalk’s and Volkmar’s bands were annihilated in Hungary

The Princes’ Crusade: Conquest and Aftermath

The properly organized crusade (1096-99) achieved remarkable success:

### Key Campaigns
– 1097: Nicaea captured through Byzantine-crusader cooperation
– 1097: Victory at Dorylaeum
– 1098: Epic siege and miraculous relief of Antioch (including discovery of the Holy Lance)
– 1099: Jerusalem captured July 15 with horrific slaughter

### Establishment of Crusader States
– County of Edessa (first founded)
– Principality of Antioch
– Kingdom of Jerusalem (with Godfrey of Bouillon as Advocate)

### Military Orders Emerge
– Knights Hospitaller (founded c. 1099)
– Knights Templar (founded 1119-20)

These orders blended monasticism with knighthood, creating a new model of religious warfare.

Legacy of the First Crusade

The Crusade’s success had profound consequences:

### Spiritual Impact
– Reinforced belief in divine favor for reformed Christianity
– Created lasting pilgrimage traditions
– Inspired generations of crusading narratives

### Social Transformations
– Nobles fabricated crusading ancestors to enhance status
– Military orders became powerful international institutions
– Jewish communities developed new martyrdom traditions

### Political Ramifications
– Strengthened papal authority
– Complicated Christian-Jewish relations for centuries
– Established crusading as an enduring ideal

The First Crusade transformed medieval society’s relationship with violence, creating institutions and ideologies that would shape European history for generations. Its paradoxical blend of piety and brutality remains one of history’s most compelling examples of how faith can both inspire and justify warfare.