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“Acies quadratum” On the square formation of the Roman army
#1
For quite some time two specific references have been troubling me, these are:

Sallust Histories Book 2 (Harvard University Press Cambridge, Massachusetts London, England 2015 John T. Ramsey.)

80 93M, 76Mc, not included in D and K

A scarcity of supplies forced Pompey and Sertorius to withdraw eastward from the territory of the Vaccaei to the region occupied by the Vascones at the foot of the Pyrenees. (Italics in the translation signifies that the text or a supplement is uncertain.)

<The townsmen gave assurances by > pledging < the sanctity of an oath> that they would observe a faithful alliance, if they were released from the siege; for previously they had vacillated between Sertorius and Pompey with a wavering peace.
Then the Roman army was withdrawn into the territory of the Vascones for the sake of grain. And Sertorius likewise altered his position: it was greatly in his interest not to lose his hope of Asia. For a few days Pompey maintained a stationary camp thanks to a means of fetching water, being separated from the enemy by just a modest valley; and the nearby communities, the Mutudurei and the ***, did not aid Pompey or Sertorius with supplies. Hunger wore out both sides. Then, however, Pompey <advanced with his line of march> in a squared formation…

Dein ta/<me>n Pompeius quadrato |<agmine procedit>***

Panegyric of Messalla

Next, as soon as the struggle of venturous battle comes, and under confronting standards the lines prepare to close, then you will not fail in forming the order of the fight, whether it be needful for the troops to draw into a square, so that the dressed line runs with level front, or it be desired to sunder the battle into two several parts, so that the army's right may hold the left and its left the right and the twofold hazard yield a double victory.
http://www.attalus.org/poetry/messalla.html

Iam simul audacis uenient certamina Martis
aduersisque parent acies concurrere signis,
tum tibi non desit faciem componere pugnae,
seu sit opus quadratum acies consistat in agmen,
rectus ut aequatis decurrat frontibus ordo,
seu libeat duplicem seiunctim cernere martem,
dexter uti laeuum teneat dextrumque sinister
miles sitque duplex gemini uictoria casus.
http://www.thelatinlibrary.com/tibullus3.html

I never could understand this square formation until I read an article called:

“The square fighting march of the Crusaders at the battle of Ascalon (1099)," Journal of Medieval Military History 11 (2013) , pp. 57-71 Georgios Theotokis

https://www.academia.edu/3058471/_The_sq..._pp._57-71

Writing about the ideal formation of the infantry when deployed with units of cavalry in the field, Nicephoros Phocas writes in his Praecepta:

The formation of the infantrymen under discussion is to be a double-ribbed square, thus called “a four-sided formation” by the ancients, which has three units on each side so that all together there are twelve units on the four sides. In case the cavalry force is quite large and the enemy does not bring along a similar number of infantry, twelve intervals should be left open.

And the more important for our case is what immediately follows: “If, on the other hand, the cavalry force is not large and the enemy does bring infantry along, eight intervals should be left open.”32

32 “Praecepta Militaria”, I. 39–51, p. 14.

The phrase by the ancients in all probability means the ancient Romans. So we have just discovered a new kind of military formation for the Roman Army, perhaps even based upon the army camp. This formation seems to me different from that of Carrhae, since that was a hollow square compared to the solid square above.
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#2
A Roman consular army in 297 BC formed a solid square against the Samnites  (Livy 10 13-14), then arrayed in battle order. So from start to finish, they started in road formation, then went to solid square and then to the standard three line arrangement. I've researched this, and have estimate going from road formation to solid square can be done, as Polybius claims in one movement. Changing from solid square to battle array can also be done in one movement. I would estimate it should not take more than 15 minutes (if that), to change into these formations. Pythagorean geometry at its best.
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#3
This is fascinating Julian and Steven.
Julian, I wonder if you could explain what the twelve units constisted of ?
And if you forgive my ignorance on the matter, the difference bewteen a hollow and solid square.
For that Livy example also, a diagram might be worth a thousand words.
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#4
Michael Collins Wrote:This is fascinating Julian and Steven.
Julian, I wonder if you could explain what the twelve units constisted of ?
And if you forgive my ignorance on the matter, the difference bewteen a hollow and solid square.
For that Livy example also, a diagram might be worth a thousand words.

Polybius has the Roman army being able to go from march formation and able to deploy facing wherever the threat was coming from. All modern historians can only give examples of one direction of attack (the easy one) from four directions of attack. The criteria is from all directions, and it should be mandatory for all modern historians describing this event to show all four. You're right Michael, a picture is worth a thousand words, but I have no intention of freely showing my extensive research for the convenience of some lazy historians to run with. 

At Ruspina, Caesar states 30 cohorts, and yes that is the number of cohorts that were present. However, Caesar is not describing the Roman march organisation...that is a different kettle of fish. The 30 cohorts do not play a role in the march organisation, but Caesar's force does have 30 cohorts if you wanted to count the cohort organisation. Just as they six centuries to a cohort. So Caesar could just have said his force consisted of 180 centuries. Caesar also could have given the number of primi ordines, superiores ordines, inferior ordines, and infimi ordines, but it still would not relate to the march organisation. Caesar is just giving the number of legionaries at Ruspina.

I read the paper on the square fighting march of the crusaders. He mentions something that isn't on many people's radar, and that is the ratio of infantry to cavalry. The Romans work this way intently. It is all about ratios with the Roman army...but thankfully not too many. The difference between the crusader square and the Roman square formation is the Romans have 16 intervals, four per side. If the crusaders have three, then it has to do with the frontage of the cavalry units. Get the size of a cavalry unit, from this the cavalry frontage will give the answer to the frontage of the square as it will be based on the ratio of infantry to cavalry.
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#5
(08-22-2019, 10:25 AM)Julian de Vries Wrote: Pompey <advanced with his line of march> in a squared formation… Pompeius quadrato <agmine procedit>***

whether it be needful for the troops to draw into a square... seu sit opus quadratum acies consistat in agmen,

I wonder if there might be a difference here between acies quadratum and agmen quadratum, the first being a battlefield formation and the second a march formation? Obviously the second was intended to facilitate deploying into the first, and any Roman march column could presumably deploy into line of battle quite quickly.

A couple of descriptions of Roman 'defensive' march formations come to mind, one from Herodian and one from Tacitus. Neither, I think, uses the phrase agmen quadratum, but that seems to be what they are describing:

Herodian (8.1.2-3): Leading his army down into level country, Maximinus drew up the legions in a broad, shallow rectangle in order to occupy most of the plain; he placed all the heavy baggage, supplies, and wagons in the center of the formation and, taking command of the rear guard, followed with his troops. On each flank marched the squadrons of armed cavalry, the Moorish javelin men, and the archers from the East.

And in this formation 'the troops... crossed the plain in good order and strict discipline'.

Tacitus (Annals I.51): [Caesar] took the road prepared either to march or to fight. A detachment of cavalry and ten auxiliary cohorts led the way, then came the first legion; the baggage-train was in the centre; the twenty-first legion guarded the left flank; the fifth, the right; the twentieth held the rear, and the rest of the allies followed.

In both cases the formation seems to be a widened column rather than a square as such - the intention being to protect the baggage train against attacks from any side. Obviously it would only be possible to keep this sort of formation in relatively open country - like the arid plain that the Crusaders would be operating in, I expect. It's interesting that Tacitus describes the enemy attacking only when "the whole line was defiling through the wood: then instituting a half-serious attack on the front and flanks, they threw their full force on the rear."

Advancing over any distance in full battlefield formation (the acies quadratum) would be very difficult, then. The terminology is perhaps hazy, but agmen quadratum was not a battlefield formation, I would suggest, but a defensive march formation designed to enable rapid deployment if required.


(08-23-2019, 10:33 AM)Steven James Wrote: The criteria is from all directions, and it should be mandatory for all modern historians describing this event to show all four.

In most cases it would quite obvious to any commander which direction the enemy was attacking from, taking into consideration possibilities of outflanking. No need, surely, to assume a formation facing in all four directions - that way, three quarters of your fighting strength would be rendered useless against the main attack?
Nathan Ross
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#6
Nathan wrote:
Advancing over any distance in full battlefield formation (the acies quadratum) would be very difficult, then.

Are you certain they did advance “in full battlefield formation?” If I take a number of small blocks, I can make many and varying geometrical shapes. I find when I change my outlook, the world looks different.

This line is interesting “so that the dressed line runs with level front, or it be desired to sunder the battle into two several parts, so that the army's right may hold the left and its left the right.” When describing Scipio’s manoeuvres at Ilipa, Polybius (11 22-24) seems to be saying the same thing: “For the cavalry and velites on the right wing came into line on the right and tried to outflank the enemy, while the heavy infantry came into line on the left; but on the left wing the heavy infantry came into line by the right, the cavalry and velites by the left. The result of this movement was that, as far as the cavalry and light infantry were concerned, their right became their left.”

Nathan wrote:
In most cases it would quite obvious to any commander which direction the enemy was attacking from, taking into consideration possibilities of outflanking. No need, surely, to assume a formation facing in all four directions - that way, three quarters of your fighting strength would be rendered useless against the main attack?

Polybius does not say that. A Roman army on the march has to be able to respond to an attack from any direction, whether it is either the right flank, left flank, van and rear. All I have seen interpreted by modern historians is an attack threatening the right flank, while the Roman army is marching in three columns, with the hastati on the right, the princeps in the centre and the triarii on the left of the princeps. When the right flank is attacked, the army is in triple acies with the hastati the first line. Investigating all four directions of attack should be a given by any historian. It opens up new avenues.
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#7
Polybius is describing an inversion of the whole battle array. How does this relate to forming a square?
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#8
Michael Collins Wrote:Polybius is describing an inversion of the whole battle array.  How does this relate to forming a square?

 Tacitus (Annals 2 16) has the Roman army arranged so that the march order could come to a halt in line of battle. Any formation, whether it be battle formation, solid square or hollow square must be  able to be performed in one continuous movement. Understanding Polybius' inversion of the whole battle array is the key to understanding the solid square and the hollow square formation.
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#9
The problem that modern units (certainly in the C18th and C19th) had with being inverted was that formation changes (other than to reverse the movement that caused them to be inverted in the first instance) from an inverted state would be difficult. I hope no one will object to me mentioning this non-Roman, non-ancient period example, but we should expect the same potential problems of a regulated, ancient army like Roman one was.
Polybius is tells us at the end of 11.23 that the troops experienced no problem in fighting to a flank having simply turned to march to that flank, but he is presenting this an unusual circumstance as he refers to it as employing "...movements which are suited to an emergency." So, how is this the key to understanding a proper, regular drill ?
Tacitus 2.16
Looks to me as Germanicus` army is simply advancing in battle array - "in line of battle" - I do not see the connection here with making a formation change.
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#10
Michael Collins Wrote:Looks to me as Germanicus` army is simply advancing in battle array - "in line of battle" - I do not see the connection here with making  a formation change.

Then let's leave it at that.
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#11
(08-23-2019, 10:33 AM)Steven James Wrote: The criteria is from all directions, and it should be mandatory for all modern historians describing this event to show all four.

In most cases it would quite obvious to any commander which direction the enemy was attacking from, taking into consideration possibilities of outflanking. No need, surely, to assume a formation facing in all four directions - that way, three quarters of your fighting strength would be rendered useless against the main attack?


I`ve been reflecting a bit on how the sub-units marched in such a square; would it make sense if the right-hand column of an Agmen Quadratum marched with its left leading and left-hand column led with its right? - These would be the army centre sub-units.

A deployment to the front then would take place on the heads of the columns with the right wing deploying to the right and the left wing to the left.

Deploying to either flank would require the one of the columns to halt and turn to the threat, but the other column would need to advance further (if an inversion of units was to be avoided) and its rearmost sub-unit would need to march the furthest to come into line.

Forming to the rear, would be possible too, but perhaps a little tricksy, with each column turning about and marching in procession until the sub-units arrived to their positions on the new front. A problem may be that the wings would be the new leading elements - and the commading officers would need to get to these positions before any movement could be ordered.

[/quote]
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