Hundred Years' War

The Hundred Years' War was fought between France and England during the late Middle Ages from 1337 to 1453.
The war lasted 116 years and started because Charles IV of France died in 1328 without an immediate male heir (a son or a younger brother). Edward III of England believed that he then had the right to become the new king of France through his mother.
Since the French did not want a foreign king, Philip VI of France said that he was king because the Salic law prevented French women from ruling or transmitting the right to rule to their sons. Both countries went to war because the English did not have that rule.
Start
When the war started, France was stronger than England as it was wealthier. French knights and heavy cavalry also enjoyed a great military reputation in all of Christendom. Also, France had about 17 million people, but England had only about 4 million people. However, France was a decentralised feudal monarchy in the middle ages and so it was less unified than England. France had an alliance with Scotland and Bohemia, and England was supported by parts of the Low Countries and by some regions in France loyal to the Plantagenet kings of England.
The English won a major victory at sea in the Battle of Sluys in 1340, which prevented France from invading England. Most of the rest of the war was fought in France. England then won an overwhelming victory at the Battle of Crecy in 1346 against all odds. The use of the English longbow and stakes to counter the French cavalry played a decisive role in that victory.
Truce
From 1348 to 1356, there was very little fighting because the Black Death killed many people in England and even more people in France. Edward, the Black Prince, then won a brilliant victory at the Battle of Poitiers for England. King John II of France was captured during the battle. The English invaded France again but were not able to take any more cities. A truce in 1360 gave England about one quarter of France. The first part of the Hundred Years' War is called the Edwardian War.
Restart
The war started again in 1369. The new king Charles V of France was more successful, with Bertrand du Guesclin as his best knight. France allied with Castile against England and Portugal, and some of the fighting spilled into Spain and Portugal. France won back most of the land that had been given to England, and Bertrand du Guesclin won great French victories at the Battles of Cocherel and of Pontvallain. A peace followed from 1389 to 1415. The second part of the war is called the Caroline War.
Henry V
The most famous part of the war began in 1415, when Henry V of England invaded France and won the infamous Battle of Agincourt, again because of his great longbowmen. Much of the French nobility is said to have been killed in the battle. King Charles VI of France was insane and unable to rule, and nearly all of his sons died young.
The queen of France, Isabeau of Bavaria, married one of her daughters to Henry V and signed the Treaty of Troyes to make Henry V the next king of France. Both Henry V and Charles VI died around the same time in 1422. The English believed that Henry V's son, Henry VI of England, was now the rightful king of France, and many French people agreed.
Charles VII
Charles VI's last son, Charles VII of France, said that he ought to be the new king, but many French people said that he did not deserve to be king because they thought he was a bastard.
The English continued to capture land in France and formed an alliance with Burgundy. They won another major victory at the Battle of Verneuil, but in 1429, Joan of Arc led the French to success at the Siege of Orleans. At the Battle of Patay the same year, French knights, led by La Hire, won a great victory, and the heavy cavalry killed most of the veteran English longbowmen. Joan regained many cities in northeastern France and brought Charles VII to his coronation, but she did not recover Paris.
She was captured by the Burgundians in 1430, convicted of heresy, and burned at the stake in 1431. After her death, the French continued to take back their territory piece by piece. France won diplomatically in 1435 with the Treaty of Arras, which made Burgundy stop being an English ally and make peace with the French. In 1450, France won another great victory at the Battle of Formigny and reconquered Normandy.
End
The war ended in 1453 by a crushing victory of the French at the Battle of Castillon in which nearly 300 cannons, made by Jean Bureau and his brother Gaspard, were used for the first time in a battle. The third and last part of the war is called the Lancastrian War.