France assumed a more active role in the politics of Christian Europe from the end of the 12th century. The most heavily populated region of Europe, the kingdom of France provided its rulers with greater resources than any of their rivals. Philip Augustus led French contingents on the most fully international of the great Crusades (1190–91), although, having once demonstrated his energy in that work of piety, he could not afterward be persuaded to renew his vow. He preferred, through dynastic schemes and opportunism, to pursue his rivalry with the Plantagenets. His ambition seems to have embraced England as early as 1193, when he married Ingeborg, whose brother, the king of Denmark, had an old claim to the throne of England. When Philip, for private reasons, repudiated Ingeborg the day after the wedding and sought to have the marriage annulled, she and her brother appealed to the pope; her case, punctuated by reconciliations with Philip dictated more by policy than by sentiment, dragged on through the pontificate of Innocent III.

Meanwhile, in 1200, Philip’s son Louis married Blanche of Castile, granddaughter of Henry II, through whom another claim to England was heralded. Louis’s career as prince was marked by aggressive designs against King John. Innocent III was prepared to recognize Louis as king of England in 1213; and the policy was dropped only after Louis’s abortive invasion of 1216–17.

It was in the play of rival coalitions that Philip Augustus had his greatest diplomatic anxiety and success. Philip countered John’s alliance with Otto IV of Brunswick, his nephew and claimant to the empire, by supporting a second claimant, Philip of Swabia. When Otto became Holy Roman emperor in 1209 and the counts of Flanders and Boulogne were alienated from their Capetian suzerain, Philip found himself seriously threatened in his northern heartlands. John’s desire to avenge the loss of his French fiefs finally prompted him to act in 1214; he led a force from the west, and his major allies marched on Paris from the north. Philip Augustus met the allied forces at Bouvines in July 1214 and won a decisive victory. As John retreated and his coalition collapsed, there could be no doubt that Capetian France had achieved hegemony in Christian Europe.

Louis IX acted astutely, though in ways unlike his grandfather’s, to preserve the prestige of France. His treaties with Aragon and England, designed to extend and secure his domains, resulted from a cordiality better appreciated abroad than by the royal counselors. From Navarra and Lorraine as well as from within the realm were brought disputes for his judgment; and in the Mise of Amiens (1264) Louis responded to the appeal of Henry III and the English barons to pronounce on the validity of the Provisions of Oxford (a written agreement between the king and magnates in England to reform the state of the realm). But the more absorbing issues of Louis’s diplomacy lay in the east. He resisted papal urgings to take sides against Otto’s successor, Frederick II, believing in the equal legitimacy of empire and papacy. On the other hand, he allowed his brother Charles I of Anjou to accept the crown of Sicily from the pope; for this enterprise, as well as for his own Crusades, he allowed the papacy to tax the French clergy. His paramount foreign interest was to recover the holy places of Christ, a traditional ambition characteristically associated in his mind with the hope of converting the infidel: the Mongols or the emir of Tunis.

Louis IX first took the cross in 1244, upon learning that a Turkish-Egyptian coalition had driven the Christians of the Levant back to precarious coastal positions. His expedition, which was well planned and well financed, set out in 1248, only to founder in the plague-ridden floodwaters of Egypt a year and a half later. Louis himself was captured; upon his release he spent four years in Syria in support of the Christian cause. He renewed his Crusader’s vow in 1267, in circumstances clouded by Angevin-Sicilian politics. Charles, whose inordinate Mediterranean ambitions had little in common with the traditional Crusade, secretly persuaded the new expedition to divert to Tunis. It broke up there with the king’s death in 1270.

The prestige of France in Christendom lost little from these failures of Louis IX. Nor was it generally foreseen that Aquitaine and Sicily would become battlegrounds in the future. The apparent strength of his father’s diplomacy deterred Philip III from changing it, even though circumstances had changed. When in 1282 the misrule of Charles of Anjou caused the Sicilians to revolt in favour of Peter III of Aragon, leading to the War of the Sicilian Vespers, a test of the Angevin policy could no longer be deferred. Charles’s friend Pope Martin IV (reigned 1281–85) excommunicated the king of Aragon and offered the vacant throne to Philip for one of his sons. Because at this juncture the crown of Navarra was destined for Philip’s son and successor, Philip the Fair, the whole Spanish March seemed ripe for recovery by the French. Yet the Crusade against Aragon, blatantly political and impractical, came to a catastrophic end: the king himself died as his battered forces staggered out of Catalonia (October 1285). Charles of Anjou and Martin IV also died in 1285. Understandably, Philip the Fair, who had foreseen the folly of the ill-conceived attack on Aragon, no longer permitted Mediterranean concerns to dominate foreign policy. The issue over Sicily dragged on, but minor Capetian interests in the Pyrenees and in Castile were allowed to lapse.

The extension of French influence and domain toward the north and east was the result of resourceful diplomacy at the expense of the empire. Philip’s interest in that direction was emphasized when his sister married the son of Albert I of Germany and when he proposed first his brother and later his son as candidates for the imperial title. But it was against the English holdings in France that Philip exercised his most aggressive and portentous diplomacy.

Questions over spheres of administrative rights in Aquitaine had been creating tensions for many years. By the Treaty of Amiens (1279) the Agenais, whose status had been left in doubt when Alphonse of Poitiers died, passed to Edward I of England, who also had unsettled claims in Quercy. Serious conflict was precipitated in 1293, when clashes between French and English seamen caused Philip the Fair to summon his vassal to Parlement. When Gascon castles occupied by the French as part of the settlement were not returned to the English on schedule, Edward renounced his homage and prepared to fight for Aquitaine. The war that ensued (1294–1303) went in favour of Philip the Fair, whose armies thrust deep into Gascony. Edward retaliated by allying with Flanders and other northern princes. His dangerous campaign, concerted with the count of Flanders in 1297, met defeat from a French force led by Robert of Artois, and during a truce from 1297 to 1303 the rival monarchs reestablished the status quo ante. Edward married Philip’s sister, and a marriage was projected between Prince Edward and Philip’s daughter.

A consequence of this first war was to be the chronic insubordination of Flanders. After the count’s surrender and imprisonment, it was left to the Flemish burghers to revolt against the French garrisons, and the French knights suffered a terrible defeat at Courtrai in July 1302. Thereafter the tide turned. But it was only in 1305 that a settlement satisfactory to the king could be reached; even then it proved impossible to win full ratification from the Flemish townsmen, whose resistance remained an invariable factor in the latent hostility between France and England.

In 1320 Philip the Fair’s son, Philip V, obtained Edward II’s personal homage, but friction was increasing in Gascony again. When Edward refused to do homage to Philip V’s brother and successor, Charles IV, an old issue relating to French rights in Saint-Sardos (in Agenais) flamed into a war that once again went in favour of the French. By the Treaty of Paris (March 1327) France recovered Agenais and Bazadais and imposed a heavy indemnity on England, but a number of issues were left unresolved. Meanwhile, having married the emperor Henry VII’s daughter, Charles was tempted to negotiate for the vacant imperial title in 1324; but nothing came of this. The last Capetians, although troubled at home, retained their international standing among neighbouring states, which were no less troubled.