What the name covers
The Hundred Years’ War is the modern name for a series of conflicts between the kings of England and France, running from 1337 to 1453. That is about 116 years, so the name is a round figure rather than an exact count. Nobody at the time called it by that name, and historians later grouped the fighting together because the same underlying dispute kept returning. The war was not continuous. Long truces, plagues, civil strife and financial exhaustion interrupted it again and again, and for many years no major armies were in the field.
The roots of the dispute
Two problems lay under the war. The first was feudal. After 1066 the kings of England also held lands in France, and by the 1300s the main remaining holding was Gascony, part of the duchy of Aquitaine in the southwest. For those lands the English king was the vassal of the French king and owed homage, a relationship that was awkward for a monarch who ruled a kingdom of his own. Disputes over jurisdiction and appeals from Gascony to the French court were a constant irritation. The wider system of lords and vassals made such overlapping loyalties normal, but it also made them dangerous.
The second problem was succession. When the last son of Philip IV died in 1328 without a male heir, the direct Capetian line ended. The French nobility chose Philip of Valois, a nephew of Philip the Fair, as Philip VI. Edward III of England was a grandson of Philip the Fair through his mother, Isabella, and he later argued that he had the better claim. French lawyers countered that a claim could not pass through a woman, and this argument became associated with what is called the Salic law, though historians note that this was largely a justification developed after the fact.
Money and trade added to the tension. England’s wool trade supplied the cloth towns of Flanders, and the counts of Flanders were tied to the French crown, so both kings had economic reasons to care about who controlled the region. France also supported the Scots against England.
Phase one: English victories
The conflict opened in 1337, when Philip VI moved to confiscate Aquitaine. In 1340 Edward formally claimed the French crown, and an English fleet won a naval victory at Sluys. The next decades brought famous English successes: the Battle of Crecy in 1346, the capture of Calais in 1347, and the Battle of Poitiers in 1356, where the French king John II was taken prisoner. The English used longbowmen and dismounted men-at-arms to defeat larger forces of mounted knights, a lesson in battle tactics that is often repeated. The Black Death of 1348 and 1349 interrupted the fighting and weakened both sides.
The Treaty of Bretigny in 1360 gave Edward III a much enlarged Aquitaine and Calais, in return for giving up his claim to the French throne, at least on paper.
Phase two: French recovery
War resumed in 1369 under the French king Charles V, who avoided pitched battles and relied on careful campaigns of reconquest, with the constable Bertrand du Guesclin as his main commander. By the 1370s the English had lost much of what they had gained. Edward III’s final years and the reign of the young Richard II were marked by money troubles, and the costs of war helped trigger the Peasants Revolt of 1381 in England. A long truce, backed by a royal marriage in 1396, brought a rare period of calm.
Phase three: Henry V and the Lancastrian high point
Peace was undone by French politics. King Charles VI suffered bouts of mental illness, and from the early 1400s the dukes of Burgundy and Orleans fought for control of the government. Henry V of England, whose father had seized the throne in what is called the Lancastrian usurpation, saw his chance. His Agincourt campaign of 1415 ended in the Battle of Agincourt, and he went on to conquer Normandy. The Treaty of Troyes in 1420 recognized him as heir to Charles VI and set aside the king’s own son, the dauphin Charles. Henry died in August 1422, shortly before Charles VI, leaving an infant son, Henry VI, as king of both realms in English eyes.
Phase four: the French victory
The English position in France depended on an alliance with Burgundy, and that alliance eventually failed. In 1429 the French cause revived with the relief of Orleans and the coronation of Charles VII at Reims, events closely linked to Joan of Arc. In 1435 Burgundy made peace with Charles VII at Arras. After a truce in the 1440s, the French reconquered Normandy by 1450 and then Gascony. The last major battle was Castillon in 1453, and Bordeaux surrendered later that year. England kept only Calais, which it held until 1558.
How it ended and what it changed
There was no final peace treaty in 1453; the fighting simply stopped, and English kings kept the French royal title for centuries. Even so, the outcome was clear. The French monarchy emerged stronger and more centralized, with a standing royal tax system and a more permanent army. The English monarchy turned inward, and military defeat and a mentally fragile king contributed to the political crisis that led toward the Wars of the Roses. The war also helped sharpen English and French identities, even if medieval people still thought mainly in terms of lords, loyalties and regions.
Many details, such as army sizes and casualty counts, come from chroniclers who often exaggerated, so figures should be read as rough estimates.