A cavalryman termed a koursor (pi. koursores) is described in 11th century and earlier military writings.
The name derives from the Latin term cursarius meaning 'raider' (from cursus: course, line of advance, running, speed, zeal) and is believed to be the etymological root of term hussar, used for a later cavalry type. The koursor had a defined tactical role but may or may not have been an officially defined cavalry type. Koursores were mobile close-combat cavalry and may be considered as being drawn from the more lightly equipped kataphraktoi. The koursores were primarily intended to engage enemy cavalry and were usually placed on the flanks of the main battle line. Those on the left wing, termed defensores, were placed to defend that flank from enemy cavalry attack, whilst the cavalry placed on the right wing, termed prokoursatores, were intended to attack the enemy's flank. Cavalry on detached duty, such as scouting or screening the main army, were also called prokoursatores. It is thought that this type of cavalry were armed identically to the heavy kataphraktoi but were armoured more lightly, and were mounted on lighter, swifter horses. Being relatively lightly equipped they were more suited to the pursuit of fleeing enemies than the heavyweight kataphraktoi. In the Komnenian period, the more heavily equipped of the kataphraktoi were often segregated to create formations of "picked lancers," presumably the remainder, being more lightly equipped, provided the koursores. A type of cavalry, differentiated from both horse archers and those with the heaviest armour, is referred to by Kinnamos in 1147 as forming a sub-section of a Byzantine army array; they are described as "those who rode swift horses", it would appear that these were the koursores.