The Battle of Agincourt — October 25, 1415 — is one of the most studied engagements of the Hundred Years War, and the prisoner massacre that occurred during it is one of the most debated episodes in medieval military history. The core facts are not in significant dispute. What is disputed is whether Henry V's decision constituted a war crime by contemporary standards, a rational military calculation, or both simultaneously.

The Sequence of Events

The morning battle at Agincourt lasted approximately three hours. The French mounted nobility, advancing across muddy ground under English longbow fire, suffered catastrophic casualties in successive charges. By early afternoon, the French forward battle was effectively destroyed, the center had collapsed, and a substantial number of French knights and men-at-arms had been taken prisoner. Contemporary estimates of the prisoners taken before the massacre range between 1,000 and 2,000 men; modern historians including Anne Curry have suggested the figure was likely toward the lower end of that range.

At some point in the early afternoon, while the third French division remained in the field and before the battle's outcome was fully determined, Henry gave the order to kill the prisoners. The immediate trigger, recorded by several chroniclers, was the appearance of what looked like a renewed French advance or a flanking threat. Some accounts — including that of the Burgundian chronicler Enguerrand de Monstrelet — mention an attack on the English baggage train by French-aligned local forces as a contributing factor.

The killing was carried out, though not uniformly. Knights and men-at-arms of the highest rank — those whose ransoms represented significant financial value — were reportedly spared by their individual captors who refused to comply. The majority of the prisoners were killed.

The Legal and Customary Framework

Medieval laws of war, codified in various forms in the period's chivalric literature and in formal instruments like the Ordinances of War issued by Henry V himself before the campaign, recognized the right to take prisoners for ransom. The ransoming of captured knights was a substantial financial institution: it funded campaigns, enriched successful soldiers, and created a set of incentives that softened some of the period's violence. Killing prisoners who had surrendered and given their parole was considered, under this framework, a violation of good faith.

"The prisoner massacre at Agincourt violated the norms of chivalric warfare as those norms were understood in 1415," writes military historian John Keegan in *The Face of Battle*. "Whether Henry knew this and acted anyway is the question the sources cannot fully answer."

Henry V's own Ordinances of War, issued at Mantes before the campaign, prohibited soldiers from killing prisoners without explicit royal command. This creates an uncomfortable irony: Henry's massacre was technically sanctioned by his own authority, which his own rules had reserved to him.

The Strategic Argument

The defensive argument for the order rests on military necessity. The English force at Agincourt was severely outnumbered — estimates of the French army range from two to one to six to one, with modern scholarship tending toward the lower figures but still placing Henry at a numerical disadvantage. The prisoners taken in the morning fighting, had they rearmed and renewed combat, could have reversed the outcome. With a second French division still in the field, the threat was not theoretical.

Anne Curry's analysis in *Agincourt: A New History* (2005), drawing on detailed examination of the muster rolls on both sides, suggests the French numerical advantage has been significantly overstated in the chronicle tradition. If the actual disparity was smaller than the chronicles indicate, the military necessity argument weakens correspondingly — Henry may have had more margin than he believed, or than he represented to contemporaries.

The pragmatic reading is that Henry's calculation was correct in the narrow tactical sense: the prisoners were killed, the third French division did not attack in force, and the battle was won. Whether the killing was therefore justified depends entirely on which framework — military necessity, chivalric law, emerging customary international law — one applies.

The Chronicle Evidence

The sources for the massacre are substantial but not unanimous. Jean de Waurin, who may have been present at the battle as a young man fighting on the French side, describes the killing. Enguerrand de Monstrelet provides a detailed account. The English chronicle tradition — including the *Gesta Henrici Quinti*, written by a royal chaplain who was present throughout the campaign — acknowledges the order but frames it in terms of necessity. The chronicler does not claim Henry acted wrongly; he claims Henry acted under compulsion.

Thomas of Elmham's account, the *Liber Metricus de Henrico Quinto*, similarly frames the order as a military response to a genuine threat. These are royally-sympathetic sources. The French sources are more critical.

The Modern Assessment

The question of whether the prisoner massacre constituted what we would now call a war crime has been debated extensively by legal historians. Christopher Phillpotts, writing in the *Journal of Medieval History*, argues that by 1415 there was a recognizable body of customary law prohibiting the killing of surrendered combatants, and that Henry's order violated it. Adam Roberts, in his contribution to *The Laws of War: Constraints on Warfare in the Western World*, takes a more contextual view, noting that military necessity provisions in the period's customary law were broad and poorly defined.

What is certain: Henry V was not ignorant of the controversy. His attempt, recorded in some accounts, to shift responsibility for the killing onto a specific group of archers rather than onto himself as commander suggests an awareness that the order required justification. Shakespeare, writing in 1599, dramatized the debate directly through the character of Fluellen and the reactions of the soldiers — and then resolved it, in the famous fourth act of *Henry V*, in the king's favor.

History has not been equally generous. The massacre is a reminder that military brilliance and moral clarity are not the same thing, and that the most celebrated victories often have a reckoning written into them.