The Makedonian phalanx -- why such depth?

[Paralus]

Interestingly whilst re-reading the accounts of Gaugamela – especially the Vulgate – I came across Diodorus’ description of the actions of the Macedonian phalanx as the engagement began. This is little different to Curtius though he omits the banging on shields routine.

Alexander (17.57.6) issues instructions to deal with the scythe chariots:

Against the threat of the scythed chariots, he ordered the infantry of the phalanx to join shields as soon as these went into action against them and to beat the shields with their spears […] if they persevered, to open gaps in the ranks such that they might ride through harmlessly.

[ho basileus parêngeile tois en têi phalangi pezois, hotan plêsiazêi ta tethrippa, sunaspisai kai tais sarisais tas aspidas tuptein]

As the battle is underway the chariots charge the Macedonian lines and the phalangites, as ordered, form into synaspismos (phalangos sunaspizousês) and duly beat their shields with their sarisae (tais sarisais pantôn tuptontôn tas aspides). The results are mixed but largely in their favour. After this, for those chariots that continue, the phalangites do indeed open their ranks and allow the chariots through.

This, on the theory supposed in this thread, makes for much movement of ranks or, should I say, half and “quarter” files. On that theory the phalanx advances to within striking distance and then the rear eight rush up into pyknosis (eight deep) so as to be “closed up for action”. This former rear eight – obedient to the king’s orders – split down by fours and rush forward so as to form synaspismos and bang sarisae on shield. This done – and many chariots turned – each second four then rushes back to the rear and then each second eight rush back to form “open order” so as to enable the phalanx to perform the action of “opening up” so as to allow the chariots through.

One imagines the sprinting of thousands of fully armed Usain Bolts – carrying sarisae – demonstrating the precision timing of the chorus line of 42nd Street.

Curtius (4.15.14-15) adds the detail of the Macedonian formation resembling a ramparts:

[…] the chariots had now charged the phalanx, and the Macedonians received the charge with a firm resolve, permitting them to penetrate to the middle of the column.Their formation resembled a rampart; after creating an unbroken line of spears, they stabbed the flanks of the horses from both sides as they charged recklessly ahead.

I would guess – given this is accurate – that the movement of these armed Usain Bolts must have resembled so many thousands of Rubic’s Cubes in constant motion!

Note also the consistent description of the phalangite shield as aspide. Clealry to Diodorus (and the others of our sources) a shield is an aspide is a shield.