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The medieval period’s faltering and largely unsuccessful steps to constrain the worst excesses of war were an important beginning.

LAWS OF WAR IN THE MODERN SENSE DID NOT EMERGE IN EUROPE until well after the terrible wars of religion and politics that marred the 80-year period from 1568 to 1648. Moves to govern the conduct of warfare began in the Early Middle Ages, but these early efforts could not be described in terms as concrete as “law.” Two concepts especially influenced this gradual development from a loose structure of moral rules to codified laws of war: One was the idea of “just war”; the other was the “ordinances of war” that sought to restrict the worst excesses of medieval warfare.

In the latter half of the 10th century, military and criminal violence pervaded every facet of life; often there was no appreciable difference between the soldier and the brigand. Historian Christopher Allmand has noted that medieval chroniclers were nearly unanimous in their depiction of the common soldier as “a symbol of something to be feared, the perpetrator of violence and destruction, whether this took the form of attacks on property (pillage and arson) or on people (murder and rape).” Often the worst offenders were not foreign raiders or invading armies but soldiers in the service of the very countries they imperiled. So dangerous did the soldier appear to the rest of society that one monastic writer of the day cynically remarked that any man who did not know how to set a church on fire was not qualified to call himself a soldier.

Secular authority was too fragmented and its reach too short for the king’s peace to quell the unrestrained violence that plagued most realms in the early medieval period. In desperation, the church tried to invoke a higher authority to protect itself as well as the most vulnerable members of society. At the Synod of Charroux in 989, the archbishop of Bordeaux declared the Pax Dei, or “Peace of God.” The Pax Dei threatened excommunication of anyone who despoiled ecclesiastic property, robbed the poor (particularly of their domestic livestock), used violence against women and children, or attacked clergymen who were not bearing arms.

The Pax Dei sought to curb the near-constant violence, but not even the threat of eternal damnation could deter a professional caste of warmongers. As a result, ecclesiastical authorities in the 11th century declared the Treuga Dei, or “Truce of God.” The Treuga was not an attempt to abolish war outright but an effort to ameliorate the damage to society from incessant and unrestrained fighting. “The result,” historian Philippe Contamine has noted, “was less to suppress war than to reserve it to a small number of authorities, possessing the monopoly of violence.” Throughout Europe, combat was banned from noon on Saturday until dawn the following Monday; it was later declared unlawful to fight on high holy days and other notable days on the ecclesiastical calendar. Within a century, the Treuga Dei had been expanded to prohibit fighting on all but 80 days of the year.


THE PROBLEM, OF COURSE, WAS THAT EVEN IN AN ERA WHEN RELIGION DOMINATED all aspects of life, the church’s authority alone was seldom enough to fully constrain the military element. War was a reality of life, and even religious commentators acknowledged that it was sometimes a grim necessity. But how to determine which conflicts were just and therefore legitimate and which were little more than criminal enterprises?

Medieval scholars were familiar with the concept of just war from the writings of St. Augustine of Hippo and St. Thomas Aquinas—authorities on reconciling Christian proscriptions against killing with the inevitable bloodshed of warfare. A consensus emerged that wars waged under the legitimate authority of kings were just, particularly when fought in defense of the realm or in reaction to an injustice; by contrast, wars of aggression or wars purely for material gain could not be just.

In the 14th century a Benedictine prior named Honoré Bouvet, relying on that philosophical foundation, argued that the structure of the law, both canonical and secular, offered the only real solution to the evils of unrestrained or unjustified warfare. The Pax Dei and Treuga Dei had classified clergy, women, children, and the elderly as noncombatants who should be spared the ravages of war. Bouvet was among the first to argue that such people should be afforded actual legal protections in war, making them noncombatants in the modern sense. Bouvet also expounded on the idea that the soldier ought to be the servant of his society rather than a threat to it.

The challenge, as always, was how to apply the rule of law to men for whom violence was a way of life. No court system then existed to prosecute atrocities in war, and no criminal code had yet been written to even define such acts as war crimes. Medieval civil society could create definitions of what was acceptable conduct in war, but in that era only the hand that wielded the sword could impose such standards on the profession of arms. It was not enough to have a rule; there also had to be people with the authority to enforce the rule and to dispense justice when the rule was violated. And to constrain the worst practices of warfare, secular powers, both royal and military, had to cooperate.

Hence military courts were established well before civil courts in most parts of Europe. In the French and English armies of the late medieval period, the constable or marshal of the army held judicial power in addition to the authority of military command. The constable of France—the commander in chief of the army, usually second in authority only to the king—convened courts to punish transgressions of military law, as did his English counterpart, the lord marshal. In this role, constable and marshal shared the aim of trying to enforce a minimum standard of acceptable behavior for soldiers, particularly when armies were in the field.

That minimum standard was sometimes very low indeed, even among those who claimed to respect the code of chivalry. Alvarez Pelayo, a Spanish cleric in the 14th century, cited 31 offenses that he insisted were common among knights and, by extension, all professional soldiers; the transgressions he cited were the same sort that had inspired the effort to curtail warfare by means of the Pax Dei some 400 years earlier. Among the worst evils common to knights, Pelayo said, were: “They commonly lived by rapine”; “They take part in unjust wars”; “They do not fight for God or the Common Weal but for booty and to increase their fortunes”; “They fight in a cruel, implacable manner to gain vengeance, to dominate and injure”; “They kill men and wage war without legitimate authority of their superiors”; and “They are often pillagers.”


PILLAGING, IN PARTICULAR, WAS ONE OF THE MOST INTRACTABLE PROBLEMS of medieval warfare. Repeated attempts to bring plundering and looting under the rule of military law fell short. These practices were inextricably associated with soldiering throughout the era and indeed were sometimes accepted behaviors, but only when restricted to certain victims. Soldiers were not supposed to despoil the citizenry of their own country, but much less protection was afforded the civilian population of the enemy. France suffered terribly from this practice of medieval warfare, since every major land battle of the Hundred Years War was fought on French soil, and the English made a veritable science of destroying nearly everything they could not carry away in their frequent chevauchées, or raids, across the French countryside. 

English soldiers demonstrated such talent for laying waste to their enemy’s resources, infrastructure, and people that in France during the 14th century the routiers—bands of freebooting soldiers who lived by extortion and pillage whenever there was no formal campaign to provide pay—came to be called “English,” no matter what language they spoke or what country they came from. It was this long­-established custom of profiteering in war, the desire to seek one’s own fortune above all else, that brought on the first real implementations of military law to restrain soldiers’ worst behaviors.

While the commanders of medieval armies may not have been as troubled by humanitarian issues as were their ecclesiastical contemporaries, they were concerned about the military liability of undisciplined soldiers in the ranks. Battles could be lost if troops left the march to pillage or broke off their pursuit of the enemy to seek plunder. So problematic was this type of behavior, and so great a danger was it to effective command and control, that those in power sometimes took extreme measures to suppress it. In one battle during the First Crusade in 1098, commanders ordered that any man who left the ranks to search for loot before the battle was safely won would have his ears and nose cut off. Several centuries later, the need to impose military discipline and suppress the depredations of pillaging resulted in some of the first formal written regulations of military law. These were the “ordinances of war” that began to appear in the 14th century.

One of the earliest examples in England was the Ordinance of Durham, issued under the writ of Richard II when his army marched on Scotland in 1385. Richard’s ordinance established the judicial responsibilities of the marshal of the army, prohibited acts such as deserting the ranks to pillage, imposed punishments for violations of these proscriptions, and clearly spelled out the royal command that the rights of civilians were not to be violated.

In 1415, at the start of the campaign in France that would culminate in the stunning English victory at Agincourt, Henry V published an even more comprehensive ordinance to govern his army’s conduct in the field. He had copies disseminated to all his subordinate commanders, written in the common English of the day, “so that thay may have playn knowlege and enfourme their men of thiez foresaide ordinauncez & articlez.”

Many of the actions that Henry’s ordinance prohibited were ones that victimized civilians: “That no manner of man be so hardy as to go into any chamber or lodging where any woman lieth in childbed, in order to robb her”; “That no manner of man be so hardy to take from no man going to the plough and harrow, cart, horse, nor ox, nor any other beast belonging to labor without payment and agreement”; and “That no manner of man beat down housing to burn, nor apple trees, pear trees…nor no other trees bearing fruit.” These regulations, enforced by strong leadership, were very effective in controlling the conduct of English soldiers. From 1415 to 1420, even French commentators noted that the regions of France under control of Henry V’s army had been spared the worst of the usual atrocities at the hands of the occupiers.

Medieval efforts to moderate the worst excesses of war through legal proscription only achieved limited results, as shown by the dreadful suffering Italy endured in the 16th century, the Low Countries during the Eighty Years’ War (1568–1648), and Germany in the Thirty Years’ War (1618–1648). But they were a beginning. Centuries would pass before international rules of war were codified into meaningful structures, with mechanisms to effectively enforce them. Yet the medieval period’s first faltering steps in this realm formed the rough outlines of the laws of war that we know today. MHQ

John A. Haymond is the author of Soldiers: A Global History of the Fighting Man, 1800–1945 (Stackpole Books, 2018), and The Infamous Dakota War Trials of 1862: Revenge, Military Law, and the Judgment of History (McFarland, 2016).


This article appears in the Summer 2019 issue (Vol. 31, No. 4) of MHQ—The Quarterly Journal of Military History with the headline: Laws of War | The Origins of Restraint

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