Pahlava infantry

[Son of Perun]

Wiesehofer says, "In comparison, the infantry was evidently of secondary importance, although according to the Christian-Syrian 'Chronicle of Arbela', Vologeses III was said to have sent 20,000 footsoldiers against the Alans in 136 AD." [Ancient Persia, p148]

It must be remembered that the main enemies for much of Parthia's history were the greeks and then the romans, both of whom had powerful heavy infantry. We know of Parthian armies through the eyes of the western authors, whose armies would have met the cavalry rather than any infantry; the infantry of the parthians could not have stood against the heavy infantry of the west. But the Chronicle of Arbela, as noted above, suggests that did the need arise the Parthians could call upon a vast reserve infantry (probably mostly archer/spearmen).

Foot

That's interesting but did actually Parthians have same army compositions in 136 AD and 272 BC?