In 1338, the story has it, a notorious French exile named Robert of Artois strutted into the London palace of King Edward III, bearing a stuffed heron on a silver platter. “Clear the way, you miserable failures,” he said to the assembled lords. “I have a heron … the most cowardly bird of all birds … And since it is cowardly, it is my intention to give the heron to the most cowardly one who lives, or who has ever lived: that is [King Edward], disinherited of the noble land of France of which he was rightful heir.”

Only a madman would talk to a medieval king in this way. But as the story goes, Edward was chastened, having been reminded of his claim to the French crown (in his capacity as grandson to Philip IV). “Since ‘coward’ is thrown up to me, I should defend myself,” the king said. “I vow and promise to God in heaven and his sweet Mother, who nourished Him, that before this year is ended … I will cross the sea, my subjects with me, and I will … set the country ablaze and there I will await my mortal enemy, Philip [VI] who wears the fleur-de-lis.”

The Vows of the Heron is fiction—a Flemish satire of the English bloodlust that would fuel the Hundred Years War between England and France. In the poem, it is not just Edward who is caught up in the bellicose spirit, but all the lords and ladies around him, each describing the coming carnage as an expression of love, courage, and Christian spirit. Walter of Manny (who would prove to be an especially brutal soldier of fortune) pledges to set a French city “aflame some morning, and I will destroy that city and kill the people and leave them with gaping mouths.” Another declares that “I would not spare church or altar, or any pregnant woman I might find.” Even the pregnant queen ghoulishly declares “that my fruit will never leave my body until you have led me to [Flanders]. And if it is ready to be born before that time, I will kill myself with a great steel knife. Thus will my soul be lost, and the fruit will perish.”