Historically, cavalry (from the French word cavalerie, itself derived from "cheval" meaning "horse") are soldiers or warriors who fight mounted on horseback. Cavalry were the most mobile of the combat arms, operating as light cavalry in the roles of reconnaissance, screening, and skirmishing in many armies, or as heavy cavalry for decisive shock attacks in other armies. 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, or horse archer. The designation of cavalry was not usually given to any military forces that used other animals for mounts, such as 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.
Cavalry had the advantage of improved mobility, and a soldier fighting from horseback also had the advantages of greater height, speed, and inertial mass over an opponent on foot. Another element of horse mounted warfare is the psychological impact a mounted soldier can inflict on an opponent.
The speed, mobility, and shock value of cavalry was greatly appreciated and exploited in armed forces in the Ancient and Middle Ages; some forces were mostly cavalry, particularly in nomadic societies of Asia, notably the Huns of Attila and the later Mongol armies. In Europe, cavalry became increasingly armoured (heavy), and eventually evolving into the mounted knights of the medieval period. During the 17th century, cavalry in Europe discarded most of its armor, which was ineffective against the muskets and cannons that were coming into common use, and by the mid-18th century armor had mainly fallen into obsolescence, although some regiments retained a small thickened cuirass that offered protection against lances, sabres, and bayonets; including some protection against a shot from distance.