Archer-Pair in Assyrian and Persian Warfare
The Assyrians had made major and highly effective use of a tactical feature common in Near Eastern warfare for many centuries. This was the archer-pair, consisting of a spearman bearing a very large, light but sturdy shield made of leather and wicker, and an archer; the spearman faced the enemy and held up the shield, behind which the archer hid and fired off volleys of arrows. The Persians called such shields spara and so named these tactical units sparabara, or “shield-bearers.” Typically, the Assyrians had lined these units up side by side, forming a single row of shield carriers backed by a single row of archers. [The Persians] increased the depth of the formation and also the number of archers per shield, producing a heavier concentration of arrow shot.
— The Persian Empire, pp. 27-28