Louis IX, that peculiar paragon of all monarchs of France, uniquely among them, and less than thirty years after his death, canonised as Saint Louis, was born in 1214. That year power in western Europe passed decisively from the House of Anjou—bellicose, arriviste, magnificent kings of England—to that of Capet—cautious, long-established, austere kings of France. Louis was, in fact, a product of both dynasties. His mother, Blanche of Castile, had been hand picked as French consort by her own notorious grandmother: Eleanor of Aquitaine, successively and controversially Queen of France and of England. In Louis IX, the attributes and destinies of his grandfather Philip II “Augustus” of France, a great king but a tepid crusader, and Richard I “the Lionheart” of England, a legendary crusader and unfortunate king, were strangely intermixed.

His father, Prince Louis of France, briefly king as Louis VIII, himself fearsomely nicknamed “the Lion,” did not fulfil the promise of that sobriquet. Against the advice of the wiser Philip II, Prince Louis in 1216 accepted the crown of England on his wife’s behalf, from a faction of dissatisfied barons who had occupied London. The French prince achieved some success against the hated King John, but after John’s death later that year, he failed to dislodge the ten-year-old Angevin heir, Henry III. The English business came close to the younger Louis’s childhood world; his formidable mother extracted war funds from her reluctant father-in-law by threatening to hand Louis and his brothers to her creditors as hostages.

Louis VIII’s short reign from 1223-26 was dominated by his involvement in the Albigensian Crusade, that disreputable enterprise in the Languedoc from which his father had always maintained a deniable distance. The king’s fatal dysentery elevated his twelve-year-old eldest son to the crown of France, and his wife, Queen Blanche, to its regency. Louis IX’s own life and education, entirely at his mother’s disposal, changed but little. The regent bloodlessly and profitably ended the Albigensian Crusade, and established her younger sons in appanages once fundamental to Angevin power, Poitiers and Anjou. Strong emotion, piety, and educational rigour characterized the upbringing of her sons.

Between 1234 and 1245, the four proverbially beautiful, accomplished and rich daughters of the Count of Provence found themselves propelled by Queen Blanche’s initiative, their family’s horse trading, and the envy of the English into marriage to Louis IX, Henry III, and the young kings’ respective younger brothers, Richard and Charles. After Louis’ victory over Henry in the field at Taillebourg in 1242, there was, effectively from 1243 and formally from 1259, a stable peace between France and England; the first for a century, and distinctly on French terms. As Louis IX himself put it:

Our wives are sisters and consequently our children are first cousins. That is why it is most important for us to be at peace with each other. Besides, I gain increased honour for myself through the peace I have made with the King of England, for he is now my vassal…

For Louis, personal morality and political strength were, even in private and to an extent proverbially unusual among medieval rulers, truly interdependent.

The results of Louis’ axiomatically Christian conduct were both visible and tangible. To his charity towards the amiably pathetic exiled Latin Emperor of Constantinople, France owes the Sainte-Chapelle, built between 1242 and 1248 to house the part of the Crown of Thorns, once a Byzantine relic, which Louis had acquired from his emperor-pensioner. Out of Louis’ genuine friendship with the humbly born chaplain Robert de Sorbon there emerged in 1253 the most renowned college of the University of Paris. Though privately amused by Robert’s proud manners, Louis always defended him from the sneers of lords and princes.

In 1240 Louis IX delivered a severe and to modern ears unsympathetic judgment. The controversy that culminated in the Disputation of Paris was fomented by Nicholas Donin, a Jewish scholar turned Franciscan friar. Donin sought to demonstrate the inferiority of the Talmud in relation to the Torah by translating the most controversial passages of the former from Hebrew into Latin and bringing them to the attention of the Christian authorities. The ensuing theological tournament pitted Donin and three other Christian theologians against the four most distinguished rabbis of France. The rabbis did not gain a sympathetic hearing from their dogmatic young king, who condemned the Talmud to the flames, and French Jewry to an ever uneasier status.

In 1244 Jerusalem, which had for fifteen years been under precarious Christian control, fell to a mercenary band of Khwarezmian Turks, loosely employed by one of the squabbling Ayyubid rulers. The news found Louis lying seriously ill; he vowed that, should he recover, he would win back the Holy City. He chose for his regent the best qualified candidate, his mother. After arranging her son’s marriage, Queen Blanche had quarrelled continuously with her daughter-in-law and jealously monopolized the influence and regard of the court. In leaving Blanche as regent for the second time while undertaking his crusade, Louis provided his people with a governor of proven ability, fulfilled his duty as a Christian monarch in the most spectacular fashion, and came of age as both man and monarch.

Louis IX put meticulous efficiency before impetuosity, spending four years in exemplary logistical preparation. The army he raised was not enormous, but its quality was extremely high: made up of the French nobility at its chivalric summit, supported by the best professional crossbowmen the king could purchase. Louis deliberately left crowds of devoted but untrained volunteers behind at his purpose-built harbour of Aigues-Mortes. So far the strategist had, throughout, overruled the saint.

Acting upon the long-remembered recommendation of the Lionheart, thirteenth-century century crusaders aimed to strike at the source of Muslim power and riches, Egypt, as a prelude to either dominating the whole region or at least regaining formerly Christian territory, including Jerusalem, by treaty. Louis followed in this path, evidently deciding that execution rather than method accounted for recent crusading misadventures. His army was united upon its difficult but coherent course; their enemies were also more divided than any in the Christian camp knew.

The army of the crusade gained the crucial Egyptian port of Damietta by assault with astounding ease. Many crusaders had heard directly from veterans of the Fifth Crusade how long and bitter had been the city’s last siege by Christian forces, in 1218-19. In fact Louis’ swift victory was due to the fact that the emir in charge of Damietta’s defence, Fakhr al-Din, had withdrawn to make a play for his ailing sultan’s throne, while the regiment he had left to bolster the defenses, finding itself thus unsupported and exposed, had deserted in disgust.

Chance had delivered to Louis a great prize at little cost. In 1219 the Ayyubid sultan had offered the crusaders Jerusalem in exchange for Damietta; at this point the fractious Cairene court of 1249 would surely have considered a similar arrangement. But the French king felt called by God to battle, not compromise. He led his forces on a perilous advance down the Nile.

Outside the town of Mansourah, they were confronted by the enemy in the field. Like Richard the Lionheart at Arsuf in 1191, Louis IX had to reckon with the indiscipline as well as the strength of the cult of chivalry, but he lacked his great-uncle’s terrifying instinct for battle. Due to the rash actions of Louis’ favourite brother, Robert of Artois, the crusaders after an initial success (which included the killing of the treacherous Emir Fakhr al-Din) lost six hundred of their most experienced knights, among them, to Louis’s grief, Robert. Rightly considering that retreat now would be fatal to his army’s morale, Louis attempted to hold his dearly won bridgehead before Mansourah, but before long he found himself trapped upon the Nile, just as previous crusaders had been in 1221. Too late, Louis now made the offer to exchange Damietta for Jerusalem, which was ignored by the sultan’s newly arrived heir. After an impossible fighting retreat, army and commander alike wracked by starvation and dysentery, in early 1250 Louis was forced to surrender himself into Muslim hands.

The king’s captivity was brief, as the Ayyubids, already in the midst of the palace revolution that would sweep them away, considered Damietta’s restoration a fair price for Louis’ release. As soon as he was at liberty, Louis made a decision that appalled his counsellors. He would not slink from the dangerous site of his humiliation back to the urgent demands of his patrimony, the greatest kingdom in Europe. Instead he insisted upon staying in the miserable coastal strip still left to the Franks of the East. For four years Louis toiled to remedy his crusade’s conspicuous failure, by dogged activity, incessant diplomacy, and heavy expenditure in the impossibly outnumbered defence of “Outremer.”

The last mainland Frankish possessions would, as it turned out, be exterminated in 1291, just over twenty years after Louis’ death. The Lord of Joinville, a nobleman from Champagne who during the crusade became one of the king’s closest friends, remembering Louis’s heroic defence years after that final catastrophe, was in retrospect amazed that the end had not come sooner upon Louis and his surviving soldiers in the early 1250s. Their force had been (according to Joinville’s wild estimate) a thirtieth of the size of the defending garrisons overcome in 1291. For Joinville the only possible explanation was

The love that God had for the king put such fear in the hearts of our enemies that they did not dare attack us.

A more prosaic or better informed commentator might have pointed to the turbulent internal state of Egypt, whose brutal but new-minted Mamluk slave-soldier elite had doubtless preferred domestic consolidation to further conquest for the immediate future.

Louis IX returned to France defeated, yet the most respected and powerful sovereign in Europe. It was a Europe rent by the conflicting ambitions of the papal and imperial parties—Guelf and Ghibelline—and in these conflicts Louis played a judicious, honourably neutral role. While Louis’s younger brother, Charles of Anjou, from 1266 built a Mediterranean empire by arrogating to himself the role of the Church’s champion, Louis IX stood aloof, avoiding any infringement of the rights of brother monarchs or risk to the peace of Christendom.

In 1270 Louis IX perished, according to the latest research of scurvy, in a manner he would have wished for: engaged in a fresh crusade, with the words “Jerusalem, Jerusalem” upon his lips. Unfortunately this North African expedition, to convert the secretly amenable (or so he was told) Emir of Tunis at sword point as a prelude to yet another joint assault on Egypt, was so patently futile that even the faithful Joinville refused to take part. The Tunis exploit had in fact been encouraged by that sinister, acquisitive monarch Charles of Anjou, who, though he really aimed at seizing Constantinople from the rump of the Byzantine Empire, settled upon an African expedition that might enrich Sicily, a kingdom which he had recently seized. Charles’ kingdom was entirely of this world; like so many similar figures before him, he paid for it dearly even before his death.

Louis IX always held himself to different and higher standards, and thus excelled, as it were incidentally, as one of France’s greatest earthly kings. His qualities, as a man and a Christian, are best summarized by a somewhat forbidding precept of his mother’s, which he revealed to Joinville. Queen Blanche was apparently in the habit of saying to Louis as a child

I love you, my dear son, as much as a mother can love her child; but I would rather see you dead at my feet than that you should ever commit a mortal sin.

To Joinville Louis transformed this slightly cold orthodoxy into something aflame with love. Joinville had, understandably, expressed a preference for a state of sin over the then-incurable condition of leprosy. Louis was unsurprised but urgent in his fatherly reprimand:

I beg you, as earnestly as I can, for the love of God, and for love of me, to train your heart to prefer any evil that can happen to the body, whether it be leprosy or any other disease, rather than let mortal sin take possession of your soul.

As Louis’s physical and mental courage was unflinching, so his faith, like his friendship, was affectionate, warm and, indeed, infectious. He stands apart as the best moral example of his iron rank and unbending age.