What is a Parthian shot?

The Parthian shot was a military tactic made famous by the Parthians, ancient Iranian people. The Parthian archers, mounted on light horse, would feign retreat; then, while at a full gallop, turn their bodies back to shoot at the pursuing enemy. The maneuver required superb equestrian skills, since the rider’s hands were occupied by his bow. As the stirrup had not been invented at the time of the Parthians, the rider relied solely on pressure from his legs to guide his horse.

You wound, like Parthians, while you fly, And kill with a retreating eye.
– Samuel Butler, An Heroical Epistle of Hudibras to His Lady (1678)

This tactic was used by most Eurasian nomads, including the Scythians, Huns, Turks, Magyars, and Mongols, and it eventually spread to armies away from the Eurasian steppe, such as the Sassanid clibanariis and cataphracts.

A notable battle in which this tactic was employed (by the Parthians) was the Battle of Carrhae. In this battle the Parthian shot was a principal factor in the Parthian victory over the Roman general Crassus.