Polo is a ball game played on horseback, a traditional field sport and one of the world's oldest known team sports. The game is played by two opposing teams with the objective of scoring using a long-handled wooden mallet to hit a small hard ball through the opposing team's goal. Each team has four mounted riders, and the game usually lasts one to two hours, divided into periods called chukkas or "chukkers". Polo has been called "the sport of kings", and has become a spectator sport for equestrians and high society, often supported by sponsorship. The progenitor of the game and its variants existed from the to the as equestrian games played by nomadic Iranian and Turkic peoples. In Persia, where the sport evolved and developed, it was at first a training game for cavalry units, usually the royal guard or other elite troops. A notable example is Saladin, who was known for being a skilled polo player which contributed to his cavalry training. It is now popular around the world, with well over 100 member countries in the Federation of International Polo, played professionally in 16 countries, and was an Olympic sport from 1900 to 1936. Arena polo is an indoor or semi-outdoor variant with similar rules, and is played with three riders per team. The playing field is smaller, enclosed and usually of compacted sand or fine aggregate, and often indoors. Arena polo has more maneuvering due to space limitations, and uses an air-inflated ball slightly larger than the hard solid ball used in field polo. Standard mallets are used, though slightly larger-head arena mallets are an option. History Origins and etymology The game's English name derives from the Balti language, from its word for 'ball', . It is cognate with the Standard Tibetan , also meaning 'ball'. Although the exact origins of the game are not certain, many scholars suggest it most likely began as a simple game played by Iranic and Turkic equestrian nomads in Central Asia. An archaic variation of polo, regionally referred to as buzkashi or kokpar, is still played in parts of Central Asia. It was developed and formalised in Ancient Iran (Persia) as "chovgan" (), becoming a national sport played extensively by the nobility. Women played as well as men. During the period of the Parthian Empire (247 BC to 224 AD), the sport had great patronage under the kings and noblemen.