The Makedonian phalanx -- why such depth?

[Sean Manning]

Furthermore, the manuals tell us that there were 'Half-file leaders'/hemilochites, and 'Quarter-file leaders'/enomotarchs. What purpose would these serve if whole files of 16 were the order in which they fought, and they never closed any further ?

In the tactical system of the manuals, the extra officers provided leaders if the phalanx closed up to the closest order (1 cubit per file, half the normal depth of 8, 12, or 16) or needed to produce a longer line than usual (2 cubits per file, half the normal depth of 8, 12, or 16). Aelian states (Aelian 4.3) that the depths he gives can be doubled or halved as the situation demands. This makes sense if the normal depths are 2 files (marching order), 1 file (fighting order), and 1/2 file (synaspimos). He mentions half-file leaders, but only mentions quarter-files in passing as part of an alternative system of terms which he doesn't use.

I think the Swiss show that pike formations deeper than 8 are perfectly practical, despite doubts by some scholars. Precise information on the depth of Swiss formations is hard to find, but their columns were much more than 8 deep.