Why did the Catholic Church declare a ban on crossbows in the Middle Ages?

First appearing in Europe during the 10th century, the crossbow offered a significant advantage over traditional longbows due to its mechanical design.

Unlike the longbow, which required years of training and physical strength, the crossbow was much easier to use and required less physical exertion.

By 1139, its effectiveness had become increasingly evident, as its ability to pierce armor and deliver deadly precision made it a formidable tool on the battlefield. 

As the centuries passed, the crossbow became commonly used in sieges and large-scale battles.

By the 12th century, it had spread across Europe, becoming a preferred weapon in armies like those of the Normans and the French.

The crossbow’s compact design made it perfect for defensive positions and castle sieges, where soldiers could fire bolts from behind cover with devastating effect.

Moreover, the weapon’s ability to reload without standing up provided soldiers with an additional layer of protection.

In battles like the Siege of Acre in 1189, crossbowmen played a decisive role in holding off enemy forces.

The crossbow’s ability to project power from a distance proved essential, as it leveled the playing field between peasants and knights in a way that had previously been unimaginable. 

Often, the Church found itself in the delicate position of balancing its Christian doctrine with the realities of conflict in a deeply fragmented Europe.

On one hand, the Church preached peace and unity among Christian nations, but on the other, it recognized the unavoidable nature of war in defending territories and political power.

As wars raged between kings and nobles, the Church's leaders, from popes to bishops, attempted to exert moral authority, by condemning violence while sanctioning certain conflicts as necessary for the ‘greater good’. 

When wars broke out between Christian kingdoms, the Church viewed them with a wary eye.

Rather than viewing violence as inherently righteous or honorable, the Church sought to minimize unnecessary bloodshed.

The ‘Peace of God’ and ‘Truce of God’ movements, which emerged in the 10th and 11th centuries, aimed to limit fighting by forbidding combat on holy days and encouraging nobles to protect the weak, including women, children, and clergy.

In particular, Popes like Urban II, who was responsible for calling the First Crusade in 1095, promoted religious wars as a way to redirect aggression away from fellow Christians and toward enemies of the faith. 

Religious wars like this received full Church support because they transformed warfare into a righteous act.

In these cases, the Church reframed the act of fighting as a moral duty, even promising spiritual rewards such as indulgences for those who took up arms.

In particular, the Knights Templar and the Teutonic Order, who were formed during the Crusades, represented the merging of religious devotion and military power, both blessed and guided by the Church.

However, not all conflicts received such moral approval. Civil wars between Christian kings, like the 12th-century Anarchy between Stephen of Blois and Empress Matilda, received disapproval from religious leaders who lamented the needless loss of life and division it caused. 

By the high Middle Ages, the Church had become deeply enmeshed in the political and military affairs of Europe.

Through its involvement in coronations, alliances, and treaties, the papacy often played the role of mediator or arbitrator in disputes between Christian rulers.

Popes like Innocent III, who reigned from 1198 to 1216, wielded political power through excommunications, interdicts, and even crusades to pressure kings into submission or reconciliation.  

It was a previous pope though, Innocent II, who was elected in 1130, who faced a turbulent and divided Christendom.

His reign began during a schism when rival claimant Antipope Anacletus II contested the papacy, which split the loyalties of European rulers and clergy.

For nearly a decade, Innocent struggled to assert his legitimacy, supported by influential allies such as Bernard of Clairvaux and King Lothair III of Germany, who helped secure his position.

By 1138, with the death of Anacletus II, Innocent II solidified his authority over the papal throne, but Europe remained embroiled in conflict.

Amid these challenges, Innocent called the Second Lateran Council in 1139, where he intended to address the disunity plaguing the Church. 

When the council convened, Innocent II sought to strengthen the Church’s control over Christian behavior, particularly with regard to violence.

At its conclusion, the council issued a decree that banned the use of crossbows, as well as other weapons like the longbow, against fellow Christians. 

When the Church banned the crossbow in 1139, it did so in response to the weapon’s unparalleled deadly power and its implication on feudal society.

Throughout the Middle Ages, knights had represented the apex of military might, relying on their expensive armor, warhorses, and combat training to dominate the battlefield.

Crossbows, however, allowed for a commoner to fell a knight from a distance. This undermined the very notion that the aristocracy held a divine or natural advantage in war.

The Church feared that this shift in power could destabilize society. 

In addition, the brutality of the weapon, which killed without the need for close combat or chivalric engagement, conflicted with the Church’s views on honorable warfare.

By allowing common soldiers to kill from a distance, the crossbow diminished the perceived valor and honor of hand-to-hand combat, where knights could prove their bravery.

This shift away from personal combat toward impersonal killing was seen as morally corrosive.

The Church, always seeking to mitigate the cruelty of war between Christians, viewed the crossbow as an enabler of indiscriminate violence, particularly in feudal conflicts where Christian soldiers fought one another. 

Following the Church’s ban on crossbows in 1139, medieval warfare did not immediately change, as the decree’s enforcement proved challenging.

Secular rulers, who valued the crossbow for its efficiency and power, often ignored the Church’s warnings.

This led to a disparity between the Church’s moral authority and the practical needs of military strategy.

While the Church condemned its use, many armies continued to rely on crossbows, especially in sieges and defensive positions where the weapon's range and accuracy proved invaluable.

For rulers engaged in constant territorial disputes, the benefits of the crossbow outweighed any concern for ecclesiastical censure. 

Moreover, many rulers saw the Church’s ban as an overreach into matters of state and military necessity.

Monarchs like Richard the Lionheart, who was renowned for his military prowess, employed crossbowmen without hesitation.

The weapon’s effectiveness in battle was too significant to abandon, and rulers often saw themselves as responsible for the security of their kingdoms, even if this meant defying papal authority.

Consequently, the ban's enforcement was inconsistent, depending largely on the ruler’s loyalty to the Church and their immediate military needs.

For many, the realities of warfare took precedence over religious mandates, which led to the crossbow’s continued widespread use across Europe. 

There were notable exemptions that allowed for their deployment in warfare against non-Christians.

The decree from the Second Lateran Council, while strict in forbidding the weapon's use between Christian armies, did not extend this prohibition to conflicts with non-Christians, particularly during the Crusades.

This loophole was intentional, as the Church had long sanctioned violence in defense of Christendom, and the crossbow proved indispensable in these holy wars.

In other words, while the Church sought to prevent internal Christian bloodshed, it still recognized the practical value of the crossbow when fighting external enemies. 

Moreover, the Church’s exemption for warfare against non-Christians reflected its broader approach to justifying violence.

The doctrine of bellum iustum, or just war, allowed for the use of force in defense of the faith, which meant that weapons like the crossbow were seen as morally acceptable in these circumstances.

The notion that warfare against non-Christians was a righteous endeavor meant that even the most devastating weapons could be used without violating the Church’s ethical teachings.

This created a moral distinction between the use of the crossbow against Christian knights and its use against Muslim warriors. 

The crossbow’s ability to penetrate armor and deliver deadly blows at long range made it invaluable in the fierce encounters with Muslim armies, which were often better equipped and more numerous.

By allowing the use of the crossbow in these campaigns, the Church justified its use as a means of defending the faith and protecting Christian pilgrims and territories.

As a result, the weapon was widely embraced by Crusader commanders, who saw it as a powerful equalizer on the battlefield. 

As time passed, crossbows continued to shape European military history despite the Church’s opposition.

In the 12th and 13th centuries, armies across Europe regularly deployed crossbowmen in crucial battles, including the famous Battle of Legnano in 1176, where Lombard League forces used crossbows to help defeat the cavalry of Frederick Barbarossa. 

Over time, the crossbow did play a role in shifting the social and political structures of medieval Europe.

By empowering common soldiers, crossbows contributed to the gradual erosion of the traditional knightly class’s dominance in warfare.

This shift would continue into the later Middle Ages and the early Renaissance, where new technologies like gunpowder and firearms further democratized combat.

The Church’s ban, while unsuccessful in curbing the weapon’s use, highlighted the growing tension between evolving military technology and the feudal system that had long been tied to the power of knights and noble warriors.

As crossbows, and later firearms, became more prevalent, the hierarchical nature of medieval warfare began to change, which laid the groundwork for more modern military systems.