Composite bows in antiquity?

[Sean Manning]

The compund bows' power was one of the main reasons that the Parthian arrows could penetrate the Roman shields and armour at Carrhae in 53 BC. Plutarch recounts that 'strange missiles are the precursors of their (the Parthians) appearance, which pierce through every obstacle.' He also wrote: 'but making vigorous and powerful shots from bows which were large and mighty and curved so as to discharge their missiles with great force.'

Ordinary bows would not have had the power to do this.

Be careful about placing too much emphasis on the difference between composite bows and self bows. There were many types of bows in the ancient world, each of which worked best at a typical size and strength but could be made stronger or weaker than average depending on the skill of the archer. Styles of arrow also affect things: the light reed with small bronze heads arrows popular in the ancient world can't absorb as much energy as more robust designs. You can make a self bow with a draw anywhere from 20 to 200 lbs draw, and the same is true for composite bows.

I think Parthian armies were effective because they had lots of good archers and horsemen, who could use the bows of the day effectively (and possibly could use stronger-than-average versions of the usual types of composite bow).