Origin of the conflict
The root causes of the conflict can be found in the demographic, economic and political crises of 14th-century Europe. The outbreak of war was motivated by a gradual rise in tension between the kings of France and England about Gascony, Flanders and Scotland. The dynastic question, which arose due to an interruption of the direct male line of the Capetians, was the official pretext.
Dynastic turmoil in France: 1316–1328
The question of female succession to the French throne was raised after the death of Louis X in 1316. Louis X left only a daughter, and his posthumous son John I lived only a few days. Furthermore, the paternity of his daughter was in question, as her mother, Margaret of Burgundy, had been exposed as an adulterer in the Tour de Nesle affair. Philip, Count of Poitiers, brother of Louis X, positioned himself to take the crown, advancing the stance that women should be ineligible to succeed to the French throne. Through his political sagacity he won over his adversaries and succeeded to the French throne as Philip V. By the same law that he procured, his daughters were denied the succession, which passed to his younger brother, Charles IV, in 1322.
Charles IV died in 1328, leaving a daughter and a pregnant wife. If the unborn child was male, he would become king; if not, Charles left the choice of his successor to the nobles. A girl ended up being born, therefore rendering the main male line of the House of Capet extinct.
By proximity of blood, the nearest male relative of Charles IV was his nephew, Edward III of England. Edward was the son of Isabella, the sister of the dead Charles IV, but the question arose whether she should be able to transmit a right to inherit that she did not herself possess. The French nobility, moreover, balked at the prospect of being ruled by Isabelle and her lover Roger Mortimer, who were widely suspected of having murdered the previous English king, Edward II. The assemblies of the French barons and prelates and the University of Paris decided that males who derive their right to inheritance through their mother should be excluded. Thus the nearest heir through male ancestry was Charles IV's first cousin, Philip, Count of Valois, and it was decided that he should be crowned Philip VI. In 1340 the Avignon papacy confirmed that under Salic law males should not be able to inherit through their mothers.
Eventually, Edward III reluctantly recognized Philip VI and paid him homage for his French fiefs. He made concessions in Guyenne, but reserved the right to reclaim territories arbitrarily confiscated. After that, he expected to be left undisturbed while he made war on Scotland.
The dispute over Guyenne: a problem of sovereignty
Tensions between the French and English monarchies can be traced back to the 1066 Norman conquest of England, in which the English throne was seized by the Duke of Normandy, a vassal of the King of France. As a result, the crown of England was held by a succession of nobles who already owned lands in France, which put them among the most powerful subjects of the French King, as they could now draw upon the economic power of England to enforce their interests in the mainland. To the kings of France, this dangerously threatened their royal authority, and so they would constantly try to undermine English rule in France, while the English monarchs would struggle to protect and expand their lands. This clash of interests was the root cause of much of the conflict between the French and English monarchies throughout the medieval era.
The Anglo-Norman dynasty that had ruled England since the Norman conquest of 1066 was brought to an end when Henry, the son of Geoffrey of Anjou and Empress Matilda and great-grandson of William the Conqueror, became the first of the Angevin kings of England in 1154 as Henry II. The Angevin kings directly ruled over more French territory than the kings of France. However, they still owed homage for these territories to the French king. From the 11th century onward, the Angevins had autonomy within their French domains, effectively neutralising the issue.
King John of England inherited the Angevin domains from his brother Richard I. However, Philip II of France acted decisively to exploit the weaknesses of John, both legally and militarily, and by 1204 had succeeded in taking control of much of the Angevin continental possessions. Following John's reign, the Battle of Bouvines (1214), the Saintonge War (1242), and finally the War of Saint-Sardos (1324), the English king's holdings on the continent, as Duke of Aquitaine (Guyenne), were limited roughly to provinces in Gascony.
The dispute over Guyenne is even more important than the dynastic question in explaining the outbreak of the war. Guyenne posed a significant problem to the kings of France and England: Edward III was a vassal of Philip VI of France because of his French possessions and was required to recognise the suzerainty of the King of France over them. In practical terms, a judgment in Guyenne might be subject to an appeal to the French royal court. The King of France had the power to revoke all legal decisions made by the King of England in Aquitaine, which was unacceptable to the English. Therefore, sovereignty over Guyenne was a latent conflict between the two monarchies for several generations.
During the War of Saint-Sardos, Charles of Valois, father of Philip VI, invaded Aquitaine on behalf of Charles IV and conquered the duchy after a local insurrection, which the French believed had been incited by Edward II of England. Charles IV grudgingly agreed to return this territory in 1325. To recover his duchy, Edward II had to compromise: he sent his son, the future Edward III, to pay homage.
The King of France agreed to restore Guyenne, minus Agen. But the French delayed the return of the lands, which helped Philip VI. On 6 June 1329, Edward III finally paid homage to the King of France. However, at the ceremony, Philip VI had it recorded that the homage was not due to the fiefs detached from the duchy of Guyenne by Charles IV (especially Agen). For Edward, the homage did not imply the renunciation of his claim to the extorted lands.
Gascony under the King of England
France in 1330.
France before 1214
French acquisitions until 1330
England and Guyenne/Gascony as of 1330
In the 11th century, Gascony in southwest France had been incorporated into Aquitaine (also known as Guyenne or Guienne) and formed with it the province of Guyenne and Gascony (French: Guyenne-et-Gascogne). The Angevin kings of England became Dukes of Aquitaine after Henry II married the former Queen of France, Eleanor of Aquitaine, in 1152, from which point the lands were held in vassalage to the French Crown. By the 13th century the terms Aquitaine, Guyenne and Gascony were virtually synonymous. At the beginning of Edward III's reign on 1 February 1327, the only part of Aquitaine that remained in his hands was the Duchy of Gascony. The term Gascony came to be used for the territory held by the Angevin (Plantagenet) Kings of England in south-west France, although they still used the title Duke of Aquitaine.
For the first 10 years of Edward III's reign, Gascony had been a major point of friction. The English argued that, as Charles IV had not acted in a proper way towards his tenant, Edward should be able to hold the duchy free of any French suzerainty. This argument was rejected by the French, so in 1329, the 17-year-old Edward III paid homage to Philip VI. Tradition demanded that vassals approach their liege unarmed with heads bare. Edward protested by attending the ceremony wearing his crown and sword. Even after this pledge of homage, the French continued to pressure the English administration.
Gascony was not the only sore point. One of Edward's influential advisers was Robert III of Artois. Robert was an exile from the French court, having fallen out with Philip VI over an inheritance claim. He urged Edward to start a war to reclaim France, and was able to provide extensive intelligence on the French court.
France was an ally of the Kingdom of Scotland as English kings had for some time tried to subjugate the area. In 1295, a treaty was signed between France and Scotland during the reign of Philip the Fair. Charles IV formally renewed the treaty in 1326, promising Scotland that France would support the Scots if England invaded their country. Similarly, France would have Scotland's support if its own kingdom were attacked. Edward could not succeed in his plans for Scotland if the Scots could count on French support.
Philip VI had assembled a large naval fleet off Marseilles as part of an ambitious plan for a crusade to the Holy Land. However, the plan was abandoned and the fleet, including elements of the Scottish navy, moved to the English Channel off Normandy in 1336, threatening England. To deal with this crisis, Edward proposed that the English raise two armies, one to deal with the Scots "at a suitable time", the other to proceed at once to Gascony. At the same time, ambassadors were to be sent to France with a proposed treaty for the French king.