Dojo Darelir, the School of Xenograg the Sorcerer

Hunnic Bow and Mongolian Release

The Byzantine horsed archer was an expert, capable of loosing arrows from either side of the horse while at full gallop, either shooting a fleeing opponent, or defending himself by a ‘Parthian’ shot over the horse’s rearquarters if he himself was fleeing. The method used was a full draw to the right ear which imparted greater poundage to the arrow. The penetrative quality of Roman equipment used at the battle of Callinicum was due to the adoption of the Hunnic bow and the Mongolian release. The Mongolian release, which uses a thumb lock, is faster, whereas the Mediterranean release, using the fingers to draw, is slower and with an oriental bow the fingers would be crushed. Procopius says the bow used by the Persians at Callinicum was much weaker and the arrows unable to pierce armour, even though the rate of delivery was greater.

Ann Hyland, The Medieval Warhorse, p. 22

Emphasis mine.