The Hundred Years War was fought because of claims by English monarchs on the French throne. The first standing armies in Western Europe since the time of the Western Roman Empire were introduced. The background to the conflict can be found 400 years earlier, in 911, when Frankish Carolingian ruler Charles the Simple allowed the Vikings of Rollo to settle in a part of his kingdom known afterwards as "Normandy" after the Normans with England including Maine, Anjou, Touraine and Aquitaine. Rollo (c.860 - c.932) was the founder and first ruler of the Viking principality in what soon became known as Normandy. He is also in some sources known as Robert of Normandy. In 885, Rollo was one of the lesser leaders of the Viking fleet which besieged Paris under Sigfred. Rollo stayed behind and was eventually bought off and sent to harry Burgundy. Sometime around 927, Rollo passed the fief in Normandy to his son, William Longsword.
The nearest to a formal English navy was the arrangement King Edward III had with the Kentish towns known as the Cinque Ports. In return for trading privileges the Cinque Ports provided a number of vessels for a period each year for royal military purposes. Edward III, King of England, began the Hundred Years War, claiming the throne of France on the death of King Philip IV in 1337. The war finally ended in the middle of the 15th Century with the eviction of the English from France, other than Calais, and the formal abandonment by the English monarchs of their claims to French territory. Various English aristocrats and royal officials held the responsibility for assembling the merchant ships in the different parts of the country to form Edward’s fleet: Sir Robert Morley brought 50 ships from the North of England, the Earl of Arundel the merchant fleet from the West of England and the Earl of Huntingdon the shipping from the Cinque Ports in Kent.
In 1324, Charles IV of France and the English king Edward II fought the short War of Saint-Sardos in Gascony. The major event of the war was the brief siege of the English fortress of La Réole, on the Garonne river. The English forces, led by the Earl of Kent (Edmund of Woodstock), were forced to surrender, after a month of bombardment from the French cannons, and after being promised reinforcements which never arrived. The war was a complete failure for England, and only Bordeaux and a narrow coastal strip now remained in English possession. By the end of the war, both France and England were able to raise enough money through taxation to create standing armies, the first time since the fall of the Western Roman Empire that there were standing armies in Western or Central Europe. Charles IV, King of France and Navarre, the youngest son of Philip IV, died in 1328, leaving only daughters, and an infant daughter yet to be born. The French nobility, however, did not want a foreigner- this principle, known as Salic Law, originated in the ancient tradition of laws belonging to the Salian Franks; the laws of Charlemagne. The specific events that led up to the war in the early 14th century began in France, where the Capetian dynasty had ruled for over 320 years.
Every king from Richard I to Edward II had engaged in warfare against French Kings on the continent. Meanwhile the English controlled Gascony, in what is now southwest France along the Atlantic coast, a territory which was a remnant of the formerly large French territories inherited from the Anglo-Norman kings. Gascony produced vital shipments of salt and wine, and was very profitable to the English nobility. Gascony was a separate fief held from the French crown, rather than a territory of England. Edward accepted Philip as King of France and gave up his claims to the French throne. In effect, England kept Gascony, in return for Edward giving up his claims to be the rightful king of France.
In 1333, Edward III went to war with King David II of Scotland, a French ally under the "Auld Alliance", and began the Second War of Scottish Independence. Philip saw the opportunity to reclaim Gascony, while England's attention was concentrated at home. However, the war was a quick success for England, and David was forced to flee to France after being defeated by King Edward and Edward Balliol, at the Battle of Halidon Hill, in July 1333. In 1336, Philip made plans for an expedition to restore David to the Scottish throne, and to also seize Gascony. Open hostilities broke out as French ships began ravaging coastal settlements on the English Channel and in 1337 Philip reclaimed the Gascon fief, citing feudal law and saying that Edward had broken his oath and in the early years of the war, allied with the nobles of the Low Countries and the burghers of Flanders. In 1341, conflict over the succession to the Duchy of Brittany began the Breton War of Succession, in which Edward backed John of Montfort and Philip backed Charles of Blois. When the war began, France had a population of fourteen million, whereas England had a population of only two million.
In July 1346, Edward mounted a major invasion across the Channel, landing in the Cotentin. Philip gathered a large army to oppose him, and Edward chose to march northward toward the Low Countries, pillaging as he went, rather than attempt to take and hold territory. Finding himself unable to outmanoeuvre Philip, Edward positioned his forces for battle, and Philip's army attacked. This, the famous Battle of Crécy, was a complete disaster for the French and victory was largely creditable to the English longbowmen. Edward proceeded north unopposed and besieged the coastal city of Calais on the English Channel, capturing it in 1347. This became an important strategic location for the English. It allowed the English to keep troops in France safely. In the same year, an English victory against Scotland in the Battle of Neville's Cross led to the capture of David II and greatly reduced the threat from Scotland.
The Battle of Crécy took place on 26 August 1346, near Crécy, in northern France and was one of the most important battles of the Hundred Years' War. The combination of new weapons and tactics used have caused many historians to consider this battle the beginning of the end of chivalry. Crécy was a battle in which a much smaller English army of approximately 12,000 men, commanded by Edward III of England and heavily outnumbered by Philip VI of France's force of between 30,000 and 40,000, was victorious as a result of superior weaponry and tactics, demonstrating the importance of the modern military concept of fire power. This battle established the military supremacy of the English/Welsh longbow over the French combination of crossbow and armoured knights. The next major battle in the Hundred Years War, the battle of Poitiers in 1356, would see another defeat for the French, under very similar conditions. French and Genoese casualties are estimated to have been from 10,000 to 30,000. The most likely figure is 12,000, including eleven princes and 1200 knights. Following the outbreak of war in 1337, the Battle of Sluys was the first great battle of the Hundred Years' War, on 23 June 1340. In the years following this battle, Edward attempted to invade France through Flanders. A French plan to trap the English force between the Seine and the Somme Rivers failed, and the English escape led to the Battle of Crécy, the second of the great battles of the war. Thus, the war was in fact a series of conflicts and is commonly divided into three or four phases: the Edwardian War (1337-1360), the Caroline War (1369-1389), the Lancastrian War (1415-1429).
In 1348, the Black Death began to ravage Europe. In 1356, after it had passed and England was able to recover financially, Edward's son and namesake, the Prince of Wales, known as the Black Prince, invaded France from Gascony, winning a great victory in the Battle of Poitiers, where the English archers repeated the same tactics used at Crécy. The new French King, John II, was captured. John signed a truce with Edward, and in his absence much of the government began to collapse. Later that year, the Second Treaty of London was signed, by which England gained possession of Aquitaine and John was freed. John eventually had to return to England as the hostages placed on his behalf had returned to France. In 1358, the peasants rose in rebellion in what was called the Jacquerie. Edward invaded France, for the third and last time, hoping to capitalise on the discontent and seize the throne, but although no French army stood against him in the field, he was unable to take Paris or Rheims from the dauphin, later King Charles V. He negotiated the Treaty of Brétigny which was signed in 1360. The English came out of this phase of the war with half of Brittany, Aquitaine (about a quarter of France), Calais, Ponthieu, and about half of France's vassal states as their allies, representing the clear advantage of a united England against a generally disunified kingdom of France.
The reign of Charles V saw the English steadily pushed back. Although the Breton war ended in their favour at the Battle of Auray, the dukes of Brittany eventually reconciled with the French throne. The Breton soldier Bertrand du Guesclin became one of the most successful French generals of the Hundred Years' War. Du Guesclin, in a series of careful Fabian campaigns, avoiding major English field armies, captured many towns, including Poitiers in 1372 and Bergerac in 1377. Although Henry IV planned campaigns in France, he was unable to put them into effect due to his short reign. In the meantime, though, the French King Charles VI was descending into madness, and an open conflict for power began between his cousin, John of Burgundy, and his brother, Louis of Orléans. After Louis's assassination, the Armagnac family took political power in opposition to John. By 1410, both sides were bidding for the help of English forces in a civil war.