Charles IV "the Fair" (1322–1328), last Capetian king of the direct line, humbled England in the War of Saint-Sardos and died leaving no son — the vacancy that opened the Hundred Years' War.
Charles IV was the third of Philip the Fair's sons to wear the crown in fourteen years, and like his brothers he died without a male heir — the dynastic catastrophe that ended three and a half centuries of father-to-son Capetian succession.
His short reign was effective at England's expense: the War of Saint-Sardos (1324) overran most of English Gascony in weeks, and the settlement he imposed — negotiated by his sister Isabella, King Edward II's estranged queen — became the springboard for her invasion of England. When Charles died in 1328, the peers passed over Isabella's son Edward III for Philip of Valois; Edward's deferred claim became the legal banner of the Hundred Years' War.
Born in 1294, Charles was the youngest son of Philip IV and grew up through the dynasty's harshest dramas — the destruction of the Templars, and the Tour de Nesle adultery scandal of 1314, in which his first wife Blanche of Burgundy was imprisoned for life. The marriage was annulled only in 1322, when he needed a queen.
He received the county of La Marche as appanage and waited through the brief reigns of his brothers Louis X and Philip V, becoming king in January 1322 when Philip died leaving only daughters — the second application of the new principle excluding women from the throne that Charles's own death would test to destruction.
"Le Bel" — the Fair — described his person, as it had his father's; the chronicles grant him the good looks of his house and not much of its force. The description that survives is of a correct, unimaginative, mildly avaricious king: he pursued his brothers' fiscal expedients — currency manipulation, prosecutions of Lombard bankers and corrupt officials — with steadiness rather than cruelty.
Toward his sister Isabella he showed the family loyalty that reshaped two kingdoms: sheltering her and her exiled lover Mortimer at the French court, and holding Gascony hostage while their invasion of England ripened — conduct his English brother-in-law's partisans called perfidy and the French court called justice on a vassal in default. Nothing recorded of him suggests he grasped that the dynasty itself was dying around the proprieties he maintained.
The centrepiece was the War of Saint-Sardos. A Gascon village priory, a royal bastide burned by English partisans, a summons Edward II ignored — and in August 1324 Charles's uncle Charles of Valois swept through the Agenais and left England holding only a coastal strip around Bordeaux. Edward, to avoid personal homage, sent his son: the future Edward III did homage for a truncated Gascony in 1325, in his mother Isabella's custody, and from that custody came the invasion that deposed Edward II in 1327.
Charles kept Navarre through his mother's inheritance, meddled profitably in Flanders, and even entertained an imperial candidacy in 1324. When he fell mortally ill at Vincennes in the new year of 1328, everything hung on the pregnancy of Queen Jeanne d'Évreux: he directed that if the child were a girl, the peers should choose the king. On 1 April she bore a daughter, and the crown passed to Philip of Valois.
Charles died on 1 February 1328 and was buried at Saint-Denis; the regency and then the crown of his cousin Philip VI followed the assembly's verdict that "no woman, nor therefore her son", could succeed to France — reasoning aimed squarely at Isabella and the sixteen-year-old Edward III.
The consequence outweighed everything he did: within a decade Edward III's renounced-and-revived claim through Isabella became the dynastic engine of the Hundred Years' War, and every later act of that conflict — Crécy, Poitiers, Troyes, Castillon — worked out the succession question that closed over Charles the Fair's grave.