Gaugamela Project - Update

[chris_taylor]

For those who provided us with information on our Gaugamela project (a
1:16 scale model of Alexander's army at Gaugamela using 6mm wargaming figures),
here's an update:

We've painted about 1000 figures so far, roughly 1/3 of the model. They include
the right flank and right wing up to and including the hydaspists.

I would have taken photos, but that's turning out to be rather more
difficult than I thought: overview photos just show dots and close-ups
of the tiny figures are all blurred.

But playing with them highlighted two things I thought were interesting:


1) Alexander must have had an exceptional grasp of geometry

Knowing Alexander's strategy, I tried to work backwards to arrive at his
eventual line up by formulating the problem in school-maths terms.

It goes something like this:

"Line A may vary between 3000 and 6000m, Line B is 6000m. Line A must
intersect line B at 2/3 of its length. The distance between the
endpoints of line A and B must never be less than x, measured
perpendicular of A onto B. The parallel distance between the end of line
A and B must not be more than y. What is the allowed range of length of
line A and angle of intersection?"

That's without the conditions for minimum / maximum line thickness and
fixed relationship between line thickness and length yet.

And if anything changed during approach, Alexander had to work it out in
his head.


2) the angle of the right flank

In the literature, there is dispute how it was arranged: Marsden says it
was parallel to the Persian battle line, others have it angled 45 - 90
degrees backwards from Alexander's main front line.

Black squares on a sheet of paper are one thing. Arranging 1000 figures
on the floor is quite another and I've come to the conclusion that the
discussion on angles is moot, for a very simple reason: visibility.

For Alexander's strategy to work, once he reached engagement distance,
every unit had to be in the right place relative to the Persian battle
line. Alexander needed to be able to see where he was going.

He couldn't afford horses, javelins or men in his line of sight. And he
certainly couldn't afford his own troops whirling up dust in front of
him.

If he approached the Persian line head-on, then the right flank must
have been angled off behind him: there is no way of keeping a wall of horses 500m
long completely straight and even a minor misalignment would have
obscured his view to his right.

And there isn't any point in having them all exactly parallel to the
Persians line anyway - the distances involved are negligable.

If Alexander approached diagonally, then the most sensible formation was
to angle the right flank at 90 degrees. Any other angle is difficult to
maintain and the difference in distances are again negligable.

I personally think he approached diagnoally - it would have
obliviated the need for passing on complicated instructions on how to "refuse"
a 3 km long front line. He controlled it himself by his angle of approach.

If he did, then I also think he must have compacted the flank down,
ie shortened and deepened it during approach.

The maximum length of the right flank was probably around 500m. Even a
minor change in the angle of march by one unit magnifies significantly
over the full length of the line up.

Compacting it down to a nearer square formation gives a leader good
control during approach and once in engagement distance, the wing
unfolds very easily - maximum walking distance for an infantry unit is
about 300 m.

And once in engagement distance, the exact angle doesn't matter anymore:
the cavalry was meant to ride out to meet the Persians. All he needed to do
was to tell them how close to let the Persians come before attacking.
That gave him control over where the cavalry battle would happen, and
just as important, it gave him control over the distance between his cavalry
and his second-line of infantry on the wing.

The last is a personal view:

Playing with the figures brought it home how fluid this battle must have
been. It gives a feel for the clarity of strategy and the relentless
drive with which he executed it.

It really looks as if Alexander's charge at Darius didn't start when he
spotted the gap in the Persian line, but when he left camp: everything
inbetween were simply adjustments to speed, angle and point of impact.

Chris.

[Paralus]

Yes, theory always becomes a bit different when one tries to imagine it in reality. Something that must always be borne in mind when reading the "Tacticians" for whom the world is a perfect space: both geometrically and physically.

For Alexander's strategy to work, once he reached engagement distance, every unit had to be in the right place relative to the Persian battle line. Alexander needed to be able to see where he was going.

He couldn't afford horses, javelins or men in his line of sight. And he certainly couldn't afford his own troops whirling up dust in front of
him.

He had the benefit of being on horseback and, contra Stone's re-enactment, so was Parmenion on the left. Also, he was at the apex of the wing in the royal ile - as Arrian describes. The flank guard was posted at an angle to this ile (epikampen). In this instance it certainly means refused and likely near to a right angle (2.8.7 and the description of the Hydaspses at 5.11.1). Thus Alexander leads the point and should see across the the Agrianians and javelin men posted across the front of his Companion cavalry.

If Alexander approached diagonally, then the most sensible formation was to angle the right flank at 90 degrees. Any other angle is difficult to maintain and the difference in distances are again negligable. I personally think he approached diagnoally - it would have obliviated the need for passing on complicated instructions on how to "refuse" a 3 km long front line. He controlled it himself by his angle of approach.

What is interesting is 3.14.2. This is rendered, in the Landmark, as follows:

For a time Alexander led his men in column, but when the cavalry, charging the Persians who were trying to surround the Macedonian's right wing, first breached the barbarian phalanx, Alexander wheeled about opposite the gap, arrayed the Companion cavalry and the nearby portion of the phalanx into a wedge formation, and led them [...] toward Darius...

Before this Arrian has twice told us that Alexander advanced to the right or "more" to the right (3.13.1&2). Here, near to the "crisis" of the battle, Alexander is described as still leading his men in column - that is, troop behind troop in line of advance. This seems quite odd: an engagement is imminent yet Alexander is leading men in column. Does this refer only to the cavalry? Not if Alexander is advancing with his cavalry and phalanx in battle order and in column (aside from his flank guards). Arrian clearly describes Alexander executing a turning movement (to his left) with the cavalry which "wheels" and attacks the Persian line. Not only this but, by the time this wheel to left is accomplished, the phalanx in that region forms up as part of a "wedge-like" formation headed by the cavalry. It is all too likely that the "nearby portion of the phalanx" (the hypaspists and Coenus' brigade) turned from column into into line and formation at this time (and the rest followed down the column). The movement is redolent of the battlefield display at Illium (1.6.1-4) and not something it can be expected to do once engaged with the enemy (below).

What then of the action that Arrian describes involving chariots charging the phalanx? Well here there is, as yet, no general engagement. The right flank guard is engaged and, certainly, having its progress impeded or stopped. Alexander feeds another unit into that flank action as the chariots charge at what, by now, must be the near stalled cavalry and the nearby phalanx (agema and the hypaspists). The infantry (hypaspists and possibly some of Coenus' men- the action is all on the right or "Alexander" wing here) are described as "separating ranks" so as to let them pass through where the "grooms" and the "royal hypaspists" (rear ranks one thinks) deal with breakthroughs. This is a difficult thing to imagine a phalanx - in close attack order (each man occupying three feet of space) - doing. It is far easier to imagine such if it were in the "open order" of six feet per man - which is the order for march (or column).

If we trust Arrian, Alexander began his rightward advance opposite Darius and his centre troops. He then continued this rightward march until Darius felt compelled to terminate it by sending his left wing cavalry out and around in a flanking movement and the chariots (of his left wing) against the companion cavalry and the hypaspists. Clearly Alexander had worked his way well towards Darius' left and was now approaching Darius' advance guard of the left.

If all that is so, your notion of a diagonal approach makes sense. Alexander did this, according to Arrian, leading his men "in column". When the opportunity came (or the clock ran out) Alexander wheeled his cavalry, his infantry turned into line and formed their part of his "wedge" and advance directly at the enemy. Again, I'd stress the right facing flank guard was deployed and advanced in battle array. The left will have been similar, wheeling to face out as Mazaeus launched his assault. That is at the time when the advance of the left ceased and added to the "break in the line" at Simmias' battalion on the left.

Thus you may be correct: Alexander advanced, in column, at a diagonal forward and right. Perhaps, like cavalry wedges and rhomboids, the syntagma of the phalanx led off their corners at this diagonal ? At the moment of decision, Alexander wheels his cavalry, the infantry turn into line forming the left end of what is now a "wedge" and the other infantry units follow as the rightward (diagonal) advance ceases. If this is near to a 45 degree diagonal, the infantry and cavalry strike back towards Darius left of centre (Companion cavalry) and the infantry "bristling with sarisai" drove across at the Persians.

Only a thought.

[chris_taylor]

Before this Arrian has twice told us that Alexander advanced to
the right or "more" to the right (3.13.1&2). Here, near to the "crisis"
of the battle, Alexander is described as still leading his men in column
- that is, troop behind troop. This seems quite odd: an engagement is
imminent yet Alexander is leading men in column.

That was my point: the general assumption seems to be that Alexander approached, stopped to arrange everyone in battle order and then went off the to the right.

I don't think he did: I think he marched out of camp and kept moving until he slammed his companions into the Persian lines.

For a start, it's difficult to bring a 3500 meter long train of men and horses to a halt. There's little point doing it if you all you want to do is get going again a few minutes later.

Imagine the Persian lines as a dartboard, lined up in the sand, then Darius is the bulls eye and from the moment he left camp, Alexander flew at him like a dart.

He himself was the tip of the dart, determining speed, angle of approach and point of impact personally.

His army was the shaft of the dart. (the analogy comes from the appearance in the model. Right wing and right flank are massive compared to the fragile, dysproportionately long line of the double phalanx. It looks like a dart).

The length of the front line was fixed initially and determined by the distance between where Alexander wanted Parmenio's left wing to be when the tip of the dart tip came into engagement distance. Thickness and density of the shaft changed during the change from marching order to battle order.

Once Parmenio was in the place where Alexander wanted the left flank cavalry battle to happen, Parmenio stopped. That anchored the back-end of the dart in the ground.

Parmenio send the order along the troops, from left to right: stop, face the enemy, hold your ground and don't lose contact with the guy on your right. Those four instructions were all that was necessary. (It failed
at the hinge between right and left wing).

A syntegma, marching 32 wide, 8 deep, now turned and became 8 wide, 32 deep - and they could stay that way, until the Persians made their next move. Their job was to hold ground and not break continuity.

If the Persian's attacked with chariots, they stepped aside and let them through. If they attacked with cavalry, the 16 back rows filtered in and formed a 16 * 16 square in battle order, without changing front line
length. Each commander could choose what was best in his section.

At the same time, at the front end, Alexander kept marching - he stretched the shaft of his dart, so to speak.

He "inclined to the right", ie he changed the angle of his approach from diagonal to parallel to the Persian lines. He kept on going until he saw the gap. When he did, he wheeled around. The leaders of his companions and hydaspists would have seen him coming back, their signal to turn into battle order and get ready to follow him.

The required extention of the front line isn't as difficult as it sounds.

* loosening the formation of the companions - about 300m (almost certainly necessary anyway, to give the horses the space to turn)

* use the hydaspists (as the most highly trained troops) to filter in 90 - 180 m

* 500 Agrianians & 250 archers "... posted angular-wise in case they should be seized anyhow by the necessity of deepening the phalanx, or of closing up the ranks" - about 60 m

* Coenus unit which Curtius says "stood in reserve" (Curtius gives marching order, so they must have been walking beside the line which eventually formed the front line) - about 150m

So the tip of the dart could have moved on, stretching the shaft by 700m before doing more complicated things, like thinnning the phalanx from 16 to 12. And there wasn't much point going far beyond 700 m - he's getting
too far away from Darius.

Does this refer only to the cavalry? Not if Alexander is advancing with his cavalry and phalanx in battle order and in column (aside from his flank guards). Arrian clearly describes Alexander executing a turning movement (to its left) with the cavalry which "wheels" and attacks the Persian line. Not only this but, by the
time this wheel to left is accomplished, the phalanx in that region forms up as part of a "wedge-like" formation headed by the cavalry. It is all too likely that the "nearby portion of the phalanx" (the hypaspists and Coenus' brigade with the Agrianinans to the right side) turned from column into into line and formation at this time (and the rest followed down the column).

exactly.

Thus you may be correct: Alexander advanced, in column, at a diagonal forward and right. Perhaps, like cavalry wedges and rhomboids, the syntagma of the phalanx led off their corners at this diagonal ?

The leaders of the syntagmas could march in the front left corner of their unit and just follow the guys in front of them. Assuming a diagnoal approach gets rid of all the complications of staggered units. Everyone follows Alexander in a straight line - which refuses the wing automatically.

For cavalry wedges and rhomboids, leading from the corners seems very likely: it's the only place where the leaders could see where Alexander was. And once the cavalry turned to face the enemy, they were in the
right place, at the front.

As Alexander wheeled around (after spotting the gap), he would have galloped passed the iles of the companions who were riding behind him, before he then turned right again to charge across the battle field.

The process of him riding past his own troops gives a simple (=failsafe) way of arranging the cavalry wedge exactly as the situation demanded: everyone who saw him galloping past was to be on the right limb of the wedge. Those who saw him charge at the Persians without riding past them first, would form the left limb.

ile 2 xxx 3 xxx 4 xxx 5 xxx 6 xxx 7 xxx 8 hydaspists

-----------------------------> alexander's agema riding past before turning across battle field, translates into a wedge formation of:

2 Hydaspist
3 8
4 7
5 6
agema

Cavalry wedge with limb length of 7:1 iles or 5:3 or 4:4 - decided at the time, and arranged at a canter.

At the moment of decision, Alexander wheels his cavalry, the infantry turn into line forming the left end of what is now a "wedge" and the other infantry units follow as the rightward (diagonal) advance ceases. If this is near to a 45 degree diagonal, the infantry and cavalry strike back towards Darius left of centre (Companion cavalry) and the infantry "bristling with sarisai" drove across at the Persians.

Judging by the distances involved, I estimate that the time between Alexander spotting the gap and his Agema crashing into it would have been less than 3 minutes. That's 3 minutes between relative calm and seeing approximately 1200 tons of horse & rider approach at 10 m per second.

Chris.

[Paralus]

There's quite an amount in that post so I'll stick to just a few points.

That was my point: the general assumption seems to be that Alexander approached, stopped to arrange everyone in battle order and then went off the to the right.

I don't think he did: I think he marched out of camp and kept moving until he slammed his companions into the Persian lines.

Agreed: on this there is little doubt. Alexander did this - in a slightly different fashion - at Issos where he had to march in column from the gates onto the plain of Issos. Here (2.8.1-4: the whole repays reading for an insight into the performance of the Philip/Alexander phalanx) he is described as leading "the men in column, but as it widened (the plain) he gradually rolled the them out into phalanx formation, bringing one battalion after another from column into line...". Polybios, quoting Kallisthenes' history (for a rather "bitchy" critique), adds further detail (12. 19.5-7; 21-21.3):

(Alexander) therefore retraced his steps through the pass, his phalanx on the van, his cavalry next, and his baggage on the rear. But that as soon as he had debouched upon the open country, he gave general orders to form up into a phalanx, at first thirty-two deep; then sixteen; and lastly, when they were nearing the enemy, eight deep." [...] Again, he says that Alexander was marching in line when he was about forty stades from the enemy. A greater blunder it is difficult to conceive. For where could one find a ground, and especially in Cilicia, twenty stades broad by forty deep, for a phalanx armed with sarissae to march in line? [...] It was, therefore much better to march twice or four times the ordinary depth of a phalanx in good order, for which sufficient ground could possibly be found. And it was easy to deploy his men quickly into the line of the phalanx, because he was able by means of scouts to ascertain the presence of the enemy in plenty of time. But in this case, beside other absurdities, while bringing his men in line across the level, he did not even (we are told) put the cavalry in front, but marched with them in the same alignment [...] But the greatest blunder is still to come. "As soon as Alexander," he says, "was within distance of the enemy he caused his men to take up order eight deep," which would have necessitated ground forty stades wide for the length of the line; and even had they, to use the poet's expression, "laid shield to shield and on each other leaned," still ground twenty stades wide would have been wanted, while he himself says that it was less than fourteen.

Ignoring the terse critique, Alexander is described as forming from column into line and then approaching reducing depth from 32 to 16 to 8. The argument over the "normal" fighting depth and whether the phalanx adopted close order from marching order by file insertion or compaction (both are attested in the "Tacticians" and the latter is clearly described in the sources - see Plb. 18.24.8 and here) is not terribly relevant though I believe that Alexander reduced to 8 so as to occupy the width of field (See Arrian, Anabasis 2.7.3. Polybios clearly says that had the phalanx, in close order, adopted syanspismos it will have compacted to half the ground).

At Issos the ground was the determining factor and Alexander advanced in battle line. The ground was not an issue on the plain at Gaugamela. Here Alexander led the army out in column and at the diagonal with the cavalry and refused wing in the van. The phalanx could turn into line at the moment Alexander desired; something not possible in the confines of Issos.

Once Parmenio was in the place where Alexander wanted the left flank cavalry battle to happen, Parmenio stopped. That anchored the back-end of the dart in the ground.

Parmenio send the order along the troops, from left to right: stop, face the enemy, hold your ground and don't lose contact with the guy on your right. Those four instructions were all that was necessary. (It failed at the hinge between right and left wing).

I would think this happened the other way around. Alexander will have decided the time to stop and turn into line. Parmenion will have been well briefed on this and would be expecting the time. I'd think the only other determining factor was the decision of Mazaeus to engage. This could not be predicted though such will likely have been delayed by the refused approach of the left. In the end Parmenion likely ordered the turn into line when Mazaeus launched his assault. Here, then, is a factor in the famous "break in the line".

A syntegma, marching 32 wide, 8 deep, now turned and became 8 wide, 32 deep - and they could stay that way, until the Persians made their next move. Their job was to hold ground and not break continuity.

I'd see the syntagma of the phalanx as in column of 16x16. These squares are far simpler to lead off the front right corner (or just as as easily off the right file). Again, the argument of 16 deep or 8 deep as fighting depth aside (I believe 16 - Plb 29.5-30.3), the files would simply "wheel" into battle line.

At the same time, at the front end, Alexander kept marching - he stretched the shaft of his dart, so to speak.

He "inclined to the right", ie he changed the angle of his approach from diagonal to parallel to the Persian lines. He kept on going until he saw the gap. When he did, he wheeled around. The leaders of his companions and hydaspists would have seen him coming back, their signal to turn into battle order and get ready to follow him.

Alexander is described as "heading more to the right" and having "continued to move to the right" (Landmark translation). This is most likely the continuation of the diagonal approach. At this time his lead units of the flank guard are contacting the Persian units Darius sends off to stop this rightward march. Eventually Alexander stops as the flank guard is heavily engaged. The Persian cavalry units that have been committed to this flanking assault present a "gap" in the Persian left of centre - near to the wing. Here it is likely that Alexander wheels to his left in line and the phalanx follows suit. Most likely the files, in column, close up to the right and then turn into line (though file insertion might be as likely after turning into line).

I do not think Alexander left or stretched his infantry. Nor do I think he crossed back in front of them. This is Stone's reconstruction. Here Alexander gallops off to Babylon before returning (after wheeling) towards his own lines. By this time his cavalry have run the equivalent of the Melbourne Cup. Alexander creating any gap between the agema of the hypaspists (and the rest of his infantry ) and his Companion cavalry was an open invitation to disaster. The agema of the hypaspists will always have been in contact with the cavalry. Thus Alexander, still approaching at the diagonal, wheels to the left and the infantry follow suit, immediately upon which the Macedonian assault commences.

So the tip of the dart could have moved on, stretching the shaft by 700m before doing more complicated things, like thinnning the phalanx from 16 to 12. And there wasn't much point going far beyond 700 m - he's getting too far away from Darius.

The Macedonian right commences its assault when it is opposite the Persian left wing. The advance commenced with Alexander opposite the Persian centre and continued until Darius feared that Alexander "was about to leave the ground the Persians had leveled" (Arr. 3.13.2) for the chariots. Thus he is oppsite, or near to, the chariots of the Persian left wing. It is these that then assault the Agrianians and the hypaspists. This Macedonian assault is launched from the diagonal though; thus it aims into the Persian centre-left with Alexander making to his left and toward Darius.

On Curtius' account, one needs to be careful. He adds details not recorded in Arrian and his "rhomboid" is a neat portrayal of the look of Alexander's array. His description is replete with error and not a little confusion though. He places Alexander's infantry guard, the Argyraspids (hypaspists) in the rear phalanx (4.13.27); Koinos' asthetairoi are "in reserve" (13.28); Krateros somehow finds himself commanding the Peloponnesian cavalry (13.29); Menidas, commander of the mercenary cavalry on Alexander's right flank guard, rides away to protect the baggage and, failing, returns (4.15.12) and the Persians pressuring Alexander's rear (4.15.22) were assaulted by the Agrianian cavalry(!!) to mention just a few.

[chris_taylor]

There's quite an amount in that post so I'll stick to just a few points.

There is indeed.

We agree the approach was diagonal
You say the syntagma was in column of 16*16, I think it was 32*8. I'm not quibbling.

The key thing that I was getting at is this:

Alexander is described as "heading more to the right" and having "continued to move to the right" (Landmark translation).

The Macedonian right commences its assault when it is opposite the Persian left wing. The advance commenced with Alexander opposite the Persian centre and continued until Darius feared that Alexander "was about to leave the ground the Persians had leveled" (Arr. 3.13.2) for the chariots. Thus he is oppsite, or near to, the chariots of the Persian left wing. It is these that then assault the Agrianians and the hypaspists. This Macedonian assault is launched from the diagonal though; thus it aims into the Persian centre-left with Alexander making to his left and toward Darius.

We agree (I think) that Parmenio was fighting on the left, while some units at the front were engaged and yet Alexander continued to march towards the right.

I don't understand how you explain the necessary lengthening of the front line?

Chris.

[Paralus]

I don't understand how you explain the necessary lengthening of the front line?

Arrian only mentions extension or contraction of the line in respect of the flank guard (3.12.2). This in relation to a Persian flanking assault and, I suppose, the extension of the line to the rear. The main infantry battle line (and the rear) will have been a fixed length: Alexander could not extend this without interfering with his flank guards.

Ignoring the rear line of Mercenary/allied hoplites, the Macedonian line has advanced diagonally in column; the file leaders being on the left. Arrian's description has the chariots attacking as the right flank guard is becoming heavily engaged; the purpose of that attack being to pin the Macedonians for the chariots. It is likely that the movement right is slowed or stopped when the chariots are launched. The Agrianians and Balacrus' men deal with those charging the Companion cavalry and the phalanx makes way for the those attacking it. At this stage, for it to allow chariots to pass within its ranks, it must still be in an open or marching order. Likely, once the chariots were launched, the phalanx "inclines to it shield" as the Tacticians have it: faces left in the direction of the shield. It has thus turned into line and is still in "open order". Chariots dome with (and Alexander can hardly have been advancing right and dealing with same), Alexander orders Aretes out of the flank guard to attack the encircling Persians continues to lead "his men on in column". This either necessitates the phalanx - led by the hypaspists - following or a break being created in the line at the crucial juncture of the cavalry and infantry. Such a break, opening the flank of the phalanx to attack, is nowhere attested and would be a tactical disaster. I can only suppose the phalanx inclined to its sarsae (faced left) and followed.

At the appointed time Alexander wheel, his phalanx again faces to its shield and closes up. The "wedge" is formed and the assault begins. The argument is then does the phalanx close up to the right (as per Philip V at Cynoscephelae) or does it do this by file insertion (rear eight inserting between files to produce an 8 man deep with double density). I'd guess the former (given Polybios' description of the charge of the phalanx "when 16 deep"). Parmenion has likely been in battle line since the launch of the chariots and, with Mazaeus' cavalry assault following, has not followed the rest of the line after Alexander resumes his rightward advance. This, then, possibly whay, as Arrian puts it, "Simmias and his battalion were unable to follow Alexander in his pursuit" (13.14.4). Mazaeus' cavalry, following after the chariots, has Parmenion and Krateros ordering the infantry of the far left into battle order and they are rooted to the spot as the taxeis of Polyperchon rightwards follow the king.