Cantabrian circle
The Cantabrian circle (Latin: circulus cantabricus) was a military tactic employed by ancient and to a lesser extent medieval horse archers. As Flavius Arrianus [1] and Hadrian [2] relate, this was the most habitual form to appear in combat of the Cantabri tribes, and Rome adopted it after the Cantabrian Wars.
A group of horse archers or mounted javelin throwers would form a single-file rotating circle. As the archers came around to face the enemy formation they would let their missile fly. The effect was a continual stream of arrows or javelins onto an enemy formation.
The tactic was usually employed against infantry and bowmen. The constant movement of the horsemen gave them an advantage against the less mobile infantry and made them harder to target by the enemy's missile troops. The maneuver was designed to harass and taunt the enemy forces, disrupt close formations and often draw part, or all, of the enemy forces into a disorganized or premature charge. This was commonly used against enemy infantry, especially heavily armed and armored slow moving forces such as the legions of the late Roman Republic and early Roman Empire.
The advantages of the Cantabrian circle is that the mounted archers do not have to make a perfect circle, allowing them to keep their distance from the enemy. The slower moving infantry have little to no hope of catching the mounted archers, putting them at a distinct disadvantage.
The Cantabrian circle is similar to other cavalry maneuvers such as the caracole and the Parthian shot.