The Makedonian phalanx -- why such depth?

[Paralus]

Frontinus' anecdote, like many of his others, can be seen as a dubious interpretation of the very same sources we have. As we have seen, it was common in Phalanx warfare for the 'elite' unit, whether guards,Agema etc to lead the army on the march, and be on the right wing in battle. Frontinus' "stoutest of his own men" is surely just Diodorus (or his source) "flower of the Macedonians". Frontinus, like Diodorus, has the left wing of the Thracians giving way first ( but doesn't mention the outflanking cavalry). Neither mentions any echeloned or oblique attack, which, had it occurred would surely have been the focus of Frontinus' anecdotal stratagem.

I rely on Hammond’s reconstruction (Philip of Macedon and A History of Greece). I personally don’t think it pushes the source material too far but wouldn’t die defending it. The "flower" will likely be his pezhetairoi which he appears to be leading on foot.

We shall have to agree to differ, I guess. My interpretation at least has the virtue of keeping Polybius uncontradictory and consistent with, I believe, other Greek authors in describing depths in 'normal/open' order, and the manuals.
Your interpretation would have Polybius completely contradict himself...

Polybios, like Thucydides, is not free from error. As I’ve stated, I think the error here arises from his ardent desire to trash Kallisthenes. More on the “open order” thingy below.

But I postulate that the term "sixteen deep phalanx" means one in 'normal/open' order …I believe, and I think Polybius' Greek readers would know/understand, that a 'sixteen deep' phalanx closed up by means of the rear half-file moving up, so that each man was on a 3 ft frontage, and the phalanx becomes 8 deep, just as Callisthenes says.

I realise that you do and I have no problem with marching in "open order sixteen deep" generally - just in this battle. Problem is I’m not interpreting anything Polybios has written; I’m simply stating what he has clearly said. That is, to repeat the final paragraph:

From this we can easily conceive what is the nature and force of a charge by the whole phalanx when it is sixteen deep. In this case those further back than the fifth rank cannot use their pikes so as to take any active part in the battle. They therefore do not severally level their pikes, but hold them slanting up in the air over the shoulders of those in front of them, so as to protect the whole formation from above, keeping off by this serried mass of pikes all missiles which, passing over the heads of the first ranks, might fall on those immediately in front of and behind them. But these men by the sheer pressure of their bodily weight in the charge add to its force, and it is quite impossible for the first ranks to face about.

“By the whole phalanx when it is sixteen deep”, not eight, ten or four. He then goes on to describe what the task of the other eleven phalangites is: the sheer pressure of their bodily weight in the charge and keeping the missiles off with their “serried mass of pikes”. I’d observe that eleven rows would constitute a “mass” serried, Anglican or Roman Catholic; three a hopeful prayer. Ditto with the "sheer pressure" added by six as opposed to fifteen.

He is clearly, in black and white, describing a charge delivered by a sixteen deep phalanx. To claim he is assuming that his readers will realise he really means eight is to interpret his words – to an end.

Also, you haven't addressed the major difficulty with the idea that 16 deep was in close order that I raised earlier, namely how do they ( the six units of sarissaphoroi, 12,000 strong) get from 16 deep in close order, on a front of a mere 750 yards, to 8 deep on a front of 1500 yards? And this doubling of front, involving troops moving almost half a mile is carried out 'close to the enemy', and must of necessity involve the flanking cavalry and light troops to move sideways, or in echelon perhaps ?

Alexander did take half the day to cover the distance from the pass to the ultimate battlefield and Darius was occupying a well prepared defensive position – he was not making the first move. Arrian is clear that Alexander’s entire advance was a leisurely matter. As well he is abundantly clear that the cavalry dispositions were attended to as the final part of setting his line. At the risk of being misleading I shall abbreviate Arrian to save space:

Up to this time his cavalry had been ranged behind the infantry; but when they advanced into the open country, he began to draw up his army in order of battle […]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

Note that this is after the phalanx has deployed, eventually, into battle line. Alexander then resumes his leisurely approach with stops to dress his line and address his men as they closed the distance between the armies. Kallisthenes’ 32 to 16 to 8 has, I’d suggest, already occurred for as Arrian clearly states several lines later:

Alexander rode about in every direction to exhort his troops to show their valour, mentioning with befitting epithets the names, not only of the generals, but also those of the captains of cavalry and infantry, and of the Grecian mercenaries as many as were more distinguished either by reputation or any deed of valour. From all sides arose a shout not to delay but to attack the enemy. At first he still led them on in close array with measured step, although he had the forces of Darius already in distant view, lest by a too hasty march any part of the phalanx should fluctuate from the line and get separated from the rest. But when they came within range of darts….

Note that the Macedonians were “still” being led on “in close array” - not open order - whilst Darius’s forces are in “distant view”. Evidently, to be "still led" they had been led to this point “in close array”. Distant would not imply under 100 yards as Arrian clearly indicates that they came within range of the darts only after they had been led on in close array and in measured step until, one presumes, the Persians were no longer “distant”.

It is highly likely that Ptolemy (Arrian) has based his account on Kallisthenes as we agree. In that case it must have been apparent in that account that the final deployment to eight deep and close array did not take place “close to the enemy” but whilst they were, at the closest, “in distant view”. It is perhaps Polybios that is indulging in “misleading” quoting?