The Makedonian phalanx -- why such depth?

[Paralus]

... Polybius/Kallisthenes ( the latter an eye-witness), as given in XII.19-22. I don't think there is any need to "interpret" what is said, for it is quite categorical.( see my post March 17):
". For with the proper intervals for marching order a stade, when the men are sixteen deep, will hold sixteen hundred, each man being at a distance of six feet from the next. " ….there is no reference to 'eleven',( that is an assumption by you) just the ranks beyond five, and this could easily mean the rear three ranks. In fact nowhere does Polybius ( or anyone else for that matter) actually say that the Macedonian phalanx ACTUALLY fought 16 deep.. The only categorical statement is the one I keep referring to, namely that the "sixteen deep phalanx" in 'normal' ( open) formation actually fought eight deep in close order.

That last is an assumption by you based on an interpretation of Polybios’ clear words to suit it. We will have to agree to disagree on your categorical assumption that the Macedonian phalanx always delivered its charge eight deep.

I have not assumed that Polybios is referring to eleven rather I make the deduction based on the plain fact of his statement “From this we can easily conceive what is the nature and force of a charge by the whole phalanx when it is sixteen deep”. There is no need to suppose he means eight at all. Should he have he might have stated so or added: “after it has closed up”. He clearly indicates the charge here is by a “whole phalanx when sixteen deep”.

To literally apply your statement with reference to “marching order” would see the Macedonian infantry only ever march sixteen deep. Polibios actually clarifies this by saying “the proper intervals for marching order a stade, when the men are sixteen deep, will hold sixteen hundred, each man being at a distance of six feet from the next” to calculate the space occupied by sixteen men. He might as easily have stated “when 32 deep” – as the infantry plainly also marched in this order as well – to calculate the space taken in that fashion. It does not follow then that sixteen deep is only ever for marching and not ever for delivering a charge.

To go back to 357/6 and Philip’s battle against the Illyrians. The term for the Macedonian file was “dekad” and the phalanx made up of “dekades”. The clear implication is that it was originally ten men. Did Philip then, when marching on Bardyllis, go from “open order” ten deep to “closed up” five deep?

Changing the subject, slightly, to the enigmatic one of where the Greek mercenaries etc that made up a third of Alexander's Heavy Infantry were, it may be significant that it is often assumed that it is just Greek cavalry that is sent to the left to bolster Parmenion's command, but Arrian actually says Alexander "sent the Peloponesian troops and other Allied divisions round to Parmenio on the left", so it is a distinct possibility that formed the left flank of the whole infantry line......

No, that is plainly wrong as Arrian is clearly speaking of horsemen:

As Alexander advanced, he found that the ground spread out a little in breadth, and he accordingly brought up his horsemen, both those called Companions, and the Thessalians as well as the Macedonians, and posted them with himself on the right wing. The Peloponnesians and the rest of the allied force of Greeks he sent to Parmenio on the left...

If he means infantry, as you infer, then Parmenio himself – until Alexander transfers the Thessalians – is the only cavalry on the left. Further, a few lines later, Arrian inconvertibly states these are cavalry:

Meantime when Alexander perceived that nearly all the Persian cavalry had changed their ground and gone to his left towards the sea, and that on his side only the Peloponnesians and the rest of the Grecian cavalry were posted there, he sent the Thessalian cavalry thither with speed...

One final interesting aside - and I have to say that I prefer Diodorus’ version of the bribing of Apollonides, more the One-Eyed’s style – but nevertheless the source material excerpted and condensed here had to be believable.

Polyaenus 4.6.19:
Antigonus was encamped opposite to the enemy, who were commanded by Eumenes, and his force was inferior in numbers. While frequent embassies passed between the two camps, Antigonus directed that, as soon as the next embassy arrived, a soldier should abruptly introduce himself, panting, and covered with dust; and inform him, the allies were at hand. Antigonus, hearing this, jumped up in pretended jubilation, and dismissed the ambassadors. The next day he extended the front of his army twice its former length, and advanced beyond the trenches. The enemy were informed by their envoys of the arrival of the allies, and when they observed the phalanx so much extended, which they supposed had a similar depth, they did not dare to hazard an engagement, but made a precipitate retreat.

One imagines, had the tactic not worked, that Antigonus will have been forced to advance eight deep in open order before “closing up” to fight 4 deep?