The Hundred Years' War, a conflict between England and France, is generally considered to have lasted 116 years, beginning in 1337 and ending in 1453. The conflict was precipitated by the failure of the French royal line to produce a clear heir, allowing the legitimate rival claim of the English King to be the pretext for war.
Origin
In 1328, King Charles IV of France died, leaving only an infant daughter. His ambitious sister, Isabella of France, wife of Edward II of England, was at the time effectively in control of England, having forced her husband to abdicate in favor of her teenage son, King Edward III of England. The young Edward III was King Charles' closest living male relative and was the only surviving male descendant of the senior line of the Capetian Dynasty through Philip IV "The Fair," King of France.
The French nobility did not want a foreigner on the throne. Citing Salic Law, they claimed that the royal inheritance could pass only through an unbroken male line, and not through a King's daughter (Isabella) to grandson (Edward). They asserted that the royal inheritance should therefore pass to Philip of Valois, through Philip IV's younger brother Charles of Valois.
In England, this was met with indifference by the nobility, and the claim was dropped.
On the other hand, at this time in history the English kings controlled Gascony, the remnant of formerly large French territories inherited from the Anglo-Norman kings. These territories were separate fiefs held from the French crown rather than territories of England, and the homage for these possessions was a matter more difficult to resolve. King Philip VI wanted Edward to recognize Philip as Edward's sovereign; Edward wanted the return of further lands lost by his father. A compromise homage in 1329 pleased neither side.
In 1333, war broke out between Edward III and a French ally, King David II of Scotland. The war was a success for the English, and David was forced to flee to France. France and Scotland were allies under the Auld Alliance, and Philip saw the opportunity to throw the English off the continent. In 1336 plans were laid for an expedition to restore King David, and for the seizure of Edward's assets in France. Open hostilities broke out as French ships began ravaging the English Channel coast. In April 1337, the French turned down the last English proposal and England declared war on France.
The War
Although the Hundred Years War technically lasted 116 years and spanned the reigns of five English and five French (Valois) kings, this period should not be viewed as one of continuous warfare, but as a series of short campaigns separated by long periods of truce or low-level raiding. The war was primarily fought on French soil, and in some ways can be viewed as a civil war in France as much as a war between nations, with the English kings acting in their capacity as French nobles, using French as well as English forces, and allying with other French nobles opposed to the Valois monarchs, such as the Counts of Flanders or the Dukes of Burgundy and Brittany. Only as the war dragged on did nationalism on both sides become dominant, generally to the detriment of England. See also:
Battles 
The war can be divided loosely into four phases -- a phase of English success under Edward III from 1337 - 1360, a phase from 1360-1400 where the French were successful in nearly driving out the English, a phase from 1400 to 1429 marked by great English victories under Henry V, and a final phase from 1429 to 1453 in which France was united under the Valois kings.
1337-1360
The first several years of the war were marked by a slow gathering of forces, with Edward crossing to Antwerp in July 1338 and gathering allies in the Low Countries and Germany for a campaign in the north. Difficulties with money and allies and continuing conflict with Scotland forced him continually to delay major operations. The French took a number of castles in poorly defended Aquitaine without making dramatic progress either. A series of raids by French and allied Genoese ships culminated when the French gathered their fleet in preparation for an invasion of England, but Edward met and defeated the fleet off Flanders at the Battle of Sluys. England was able to dominate the English Channel for the rest of the war, preventing French invasions.
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, who was initially successful. Action for the next few years focused around a back and forth struggle in Brittany, with the city of Vannes changing hands several times, and further campaigns in Gascony with mixed success for both sides.
In July 1346, Edward mounted a major invasion across the Channel, landing in the Cotentin peninsula of Normandy, and marching through Normandy. 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 him at the Battle of Crecy. The much larger French army made a series of piecemeal attacks against the expert English archers, and all of the attacks were dispersed with heavy losses until the French were forced to retreat. Edward proceeded north unmolested, and besieged the city of Calais, capturing it in 1347. 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.
Desultory war in Brittany continued, including notable incidents of chivalry such as the Battle of the Thirty in 1351 during which 30 French knights from Chateau Josselin called out and defeated 30 English knights. In keeping with tradition, the French ransomed many of the defeated English, including knights such as Knollys (Canolles) and Cavely who would continue to fight against France more successfully.
Edward's son, Edward the Black Prince, invaded France from Gascony in 1356 and won a great victory in the Battle of Poitiers, where the English archers again repulsed French attacks with heavy loss, and the Gascon noble Captal de Buch led a flanking movement that succeeded in capturing the new Valois king, John II of France, and many of his nobles. John signed a truce with Edward, and in his absence much of the government began to collapse.
In 1358, a peasant revolt called the Jacquerie took place. It was caused in part by the deprivations suffered by the country people during the war and their hatred of the local nobility. Led by Guillaume Kale (Carle or Cale), they joined forces with other villages, and beginning in the area of Beauvais, north of Paris, committed atrocities against the nobles and destroyed many chateaux in the area. All the rebellious groups were defeated later that summer and reprisals followed.
Edward invaded France, hoping to capitalize 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 Charles V, and he negotiated the Treaty of Brétigny, renouncing the French crown but greatly expanding his territory in Aquitaine and confirming his conquest of Calais.
1360-1400
The reign of Charles V saw the English steadily pushed back. Although their claimant, John V of Brittany, defeated and killed Charles of Blois at the Battle of Auray, John and his heirs eventually reconciled with the French kings. Breton commander Bertrand du Guesclin, who went over to the Charles V, became one of his most successful generals.
A contemporaneous war in Spain occupied the Black Prince's efforts from 1366. Pedro the Cruel, whose daughters Constance and Isabella were married to the Black Prince's brothers John of Gaunt and Edmund of Langley, linking these royal houses, was deposed by Henry II of Castile in 1370 with the support of Du Guesclin and Henry II went to war against England and Portugal.
Just before New Year's Day 1370, the English Seneschal of Poitou, John Chandos, was defeated at the bridge at Chateau Lussac. The loss of this commander was a significant blow to the English. Captal de Buch was also captured and locked up by Charles V who, like the English, was not bound by outdated chivalry. Du Guesclin continued a series of careful campaigns, avoiding major English field forces, but capturing town after town, including Poitiers in 1372 and Bergerac in 1377, until his death in 1380.
In 1376, the Black Prince died, and upon the death of Edward III in 1377, Richard II became King of England. It was not until Richard had been deposed by his cousin Bolingbroke (Henry IV of England), that the English under the House of Lancaster would forcefully revive their claim to the French throne.
Henry V and the civil war between Burgundy and Armagnac
Henry IV made plans for campaigns in France, but was unable to complete them 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.
The new English King, Henry V, turned down an Armagnac offer in 1414 to restore the 1369 frontiers in return for support, demanding a return to the full territories of Henry II. In August 1415 he landed with an army at Harfleur in Normandy, taking the city. Although tempted to march on Paris directly, he elected to make a raiding expedition across France toward English-occupied Calais. In a campaign reminiscent of Crecy, he found himself outmanouvered and low on supplies, and had to make a stand against a much larger French army at the Battle of Agincourt north of the Somme. In spite of his disadvantages, his victory was near-total, and the French defeat was catastrophic, losing many of the Armagnac leaders.
In subsequent campaigns, Henry took much of Normandy, including Caen in 1417 and Rouen on January 19, 1419, placing Normandy under English rule after over 200 years of French control. He made formal alliance with the Burgundians, who had taken Paris, after the Armagnac execution of John of Burgundy in 1419. In 1420, Henry met with the mad king Charles VI, who signed the Treaty of Troyes, by which Henry would marry Charles' daughter Catherine of Valois and Henry's heirs would inherit the throne of France. The Dauphin, Charles VII, was declared illegitimate. Henry formally entered Paris later that year and the agreement was ratified by the French Estates-General.
After Henry's early death in 1422, almost simultaneously with that of his father-in-law, his baby son was crowned King Henry VI of England and also King of France, but the Armagnacs remained loyal to Charles VI's son, the dauphin Charles, and the war continued in central France.
Jeanne d'Arc and Charles VII
By 1424, the uncles of Henry VI had begun to quarrel over the infant's regency, and one, Humphrey, Duke of Gloucester, married Jacqueline, Countess of Hainaut, and invaded Holland to regain her former dominions, bringing him into direct conflict with Philip III, Duke of Burgundy.
By 1428, the English were ready to pursue the war again, laying siege to Orléans. Their force was insufficient to fully invest the city, but larger French forces remained passive. In 1429, Jeanne d'Arc convinced the Dauphin to send her to the siege, saying she had received visions from God telling her to drive out the English. She raised the morale of the local troops and they attacked the English redoubts, forcing the English to lift the siege. Jeanne proceeded to win several battles against the English, opening the way for the Dauphin to march to Reims for his coronation as Charles VII.
After Jeanne was captured by the Burgundians in 1430 and later sold to the English and executed, the French advance stalled in negotiations. But, in 1435, the Burgundians under Philip the Good switched sides, signing the Treaty of Arras and returning Paris to the King of France. Burgundy's allegiance remained fickle, but their focus on expanding their domains into the Low Countries left them little energy to intervene in France. The long truces that marked the war also gave Charles time to reorganize his army and government, replacing his feudal levies with a more modern profesional army that could put its superior numbers to good use, and centralizing the French state.
By 1449, the French had retaken Rouen, and in 1450, the count of Clermont and Arthur III, Duke of Brittany caught an English army attempting to relieve Caen at the Battle of Formigny and defeated it, using cannon to break up the archers. The French proceeded to capture Cherbourg on July 6 and Bordeaux and Bayonne in 1451. The Earl of Shrewsbury's attempt to retake Gascony, though initially welcomed by the locals, was crushed by Jean Bureau and his cannon at the Battle of Castillon in 1453.
The continuing English claim to the French throne
Following an episode of insanity for Henry VI in 1453 and the subsequent outbreak of the Wars of the Roses (1455 - 1487), the English were no longer in any position to pursue their claim to the French throne and lost all their land on the continent, except for Calais.
Calais would know the rule of eight more English Kings and Queens of France until 1558:
Edward IV of England (March 4, 1461 - April 9, 1483).
Edward V of England (April 9 - June 25, 1483).
Richard III of England (June 25, 1483 - August 22, 1485).
Henry VII of England (August 22, 1485 - April 21, 1509).
Henry VIII of England (April 21, 1509 - January 28, 1547).
Edward VI of England (January 28, 1547 - July 6, 1553).
Lady Jane Grey (July 10 - July 19, 1553).
Mary I of England (July 19, 1553 - January 7, 1558).
Ill feeling between the two nations continued well into the 16th century. Calais was captured by French troops under Francis, Duke of Guise on January 7, 1558. Mary would continue, however, to be styled Queen of France for the rest of her reign (January 7 - November 17, 1558). As did her half-sister and successor Elizabeth I of England (November 17, 1558 - March 24, 1603).
Elizabeth died childless. Her successor was her second cousin twice removed James VI of Scotland. The thrones of England and Scotland were joined in a personal union until 1707. The seven monarchs of this period would continue to use the style King/Queen of France. Their claim was however merely nominal. None of them was willing to engage in military campaigns against the actual Kings of France Henry IV, Louis XIII and Louis XIV of France.:
James VI of Scotland/James I of England (March 24, 1603 - March 27, 1625).
Charles I of England and Scotland (March 27, 1625 - January 30, 1649).
Charles II of England and Scotland (January 30, 1649 - February 6, 1685).
James VII of Scotland/James II of England (February 6, 1685 - February 12, 1689).
Mary II of England and Scotland (February 13, 1689 - December 28, 1694).
William III of England/William II of Scotland (February 13, 1689 - March 8, 1702).
Anne of England (March 8, 1702 - May 1, 1707).
The Act of Union 1707 declared the joining of the Kingdom of England with the Kingdom of Scotland to a new Kingdom of Great Britain. The Kingdom would have four Monarchs until 1801. They would also style themselves Queen/King of France. However none of them actually questioned the rights of Louis XIV and his successors Louis XV, Louis XVI, Louis XVII and Louis XVIII. The Kingdom of France itself had been abolished on September 21, 1792, replaced by the French First Republic:
Anne of Great Britain (May 1, 1707 - August 1, 1714).
George I of Great Britain (August 1, 1714 - June 11, 1727).
George II of Great Britain (June 11, 1727 - October 25, 1760).
George III of Great Britain (October 25, 1760 - January 1, 1801).
The Act of Union 1800 declared the joining of the Kingdom of Great Britain with the Kingdom of Ireland to a new United Kingdom of Great Britain and Ireland. George III chose to drop his claim to the French Throne, whereupon the fleur de lis, part of the coat of arms of all claimant Kings of France since the time of Edward III, was also removed.
However it should be noted that the change was not acknowledged by then current Jacobite claimant Henry Benedict Stuart. He continued to style himself King of France until his death on July 13, 1807. None of his own successors has made a public claim to the title.
See also:
Battles
Painting by Frank Craig. 1874-1918. Jeanne leading the army with an over dimensioned banner. 
