"with this Parthian shaft"

Parthian shot, from a carved plate in the British Museum
Creative Commons AttributionParthian shot, from a carved plate in the British Museum - Credit: J. Lendering / M. Prins
The Parthian shaft was a cavalry manoeuvre used by the Parthians, who lived in what is now Iran.  Riders armed with bows would pretend to retreat, then turn in their saddles and shoot over their shoulders at their pursuers.