Advantage of the Pilum over Bows and Arrows?

[Sean Manning]

Isn't there a big difference between the types of bow? The Parthians, who used composite bows, were first superior to Roman legionaries, until the adapted themselves and added archers to their units. That would suggest that at least composite bows are superior. The same happened in the fifth century: if I understand it correctly, with all their missiles, the Roman cavalry forces were unable to deal with the Huns, and the Byzantines had to adapt to their opponent. By doing this,they overcame the Avars.

There is, but each technology allows a wide range of bows to be constructed. You can make a tall yew self bow with a draw weight of anywhere from 20 to 200 pounds for example. There are a variety of designs of composite bow with different strengths and weaknesses. The type of arrow used is also important ... longer or shorter ones allow longer or shorter draws, and lighter arrows are usually longer ranged but suited for weaker bows. I've seen it argued that bows got stronger around Parthian times and again in Avar times and the evidence seems reasonably good.

Parthian bows may have been stronger or more efficient than earlier bows, but I think the Romans lost at Carrae because they hadn't fought a whole army of horse-archers before and were out-generalled. I would guess that Parthian skill and tactics were more important than a difference between their bows and whatever Crassus's auxilliae used.