Hundred Years' War: The army of Henry V of England, consisting mostly of archers, unexpectedly defeated the numerically superior French cavalry at the Battle of Agincourt on Saint Crispin's Day.

The Hundred Years' War was a conflict between the kingdoms of England and France and a civil war in France during the Late Middle Ages. It emerged from feudal disputes over the Duchy of Aquitaine and was triggered by a claim to the French throne made by Edward III of England. The war grew into a broader military, economic, and political struggle involving factions from across Western Europe, fuelled by emerging nationalism on both sides. The periodisation of the war typically charts it as taking place over 116 years. However, it was an intermittent conflict which was frequently interrupted by external factors, such as the Black Death, and several years of truces.

Henry V, also called Henry of Monmouth, was King of England from 1413 until his death in 1422. Despite his relatively short reign, Henry's outstanding military successes in the Hundred Years' War against France made England one of the strongest military powers in Europe. Immortalised in Shakespeare's "Henriad" plays, Henry is known and celebrated as one of the greatest warrior-kings of medieval England.

Historically, cavalry are groups of soldiers or warriors who fight mounted on horseback. Until the 20th century, cavalry were the most mobile of the combat arms, operating as light cavalry in the roles of reconnaissance, screening, and skirmishing, or as heavy cavalry for decisive economy of force and shock attacks. An individual soldier in the cavalry is known by a number of designations depending on era and tactics, such as a cavalryman, horseman, trooper, cataphract, knight, drabant, hussar, uhlan, mamluk, cuirassier, lancer, dragoon, samurai or horse archer. The designation of cavalry was not usually given to any military forces that used other animals or platforms for mounts, such as chariots, camels or elephants. Infantry who moved on horseback, but dismounted to fight on foot, were known in the early 17th to the early 18th century as dragoons, a class of mounted infantry which in most armies later evolved into standard cavalry while retaining their historic designation.