The mechanism of Roman line relief

[Justin Swanton]

A post in another thread prompted me to submit this proposed mechanism for line relief in the Republican legion. Essentially the doubled maniples of Principes come up behind the embattled Hastati. The Hastati begin to fall back through the gaps between the Principes whilst the Principes' posterior maniples, file by file, move up to occupy the gaps between the anterior maniples. The Hastati keep backing through the narrowing gap, always facing the enemy, until the final file closes the gap completely, at which point the last engaged Hastati filter back directly through the files of the Principes.

This would seem to square with the ancient sources and provide a mechanism that enables line relief to take place whilst the legion is engaged with the enemy.

The diagrams below illustrate this mechanism. The brown troops are the enemy, the green the Hastati, and the red the Principes.

[Justin Taylor]

Just remember it should be Roman legion, line relief continued in the Imperial armies as well.

Personally I go with the single file idea. The man of the new unit lets the men of the old unit go past him. Thus no one takes their eyes of the enemy and the whole tired unit is simply replaced in combat by the unit behind it.

Tricky but if you are trained for it not a problem. However both the unit replaced and replacing have to follow the plan.

Oh and it does not need men to go sideways before going back thus following KISS.

[Erpingham]

My immediate query would be whether the Romans would have conducted any line relief system while actually in contact with the enemy, rather than awaiting a lull in the action.  Not only is there much greater risk of it all going pear shaped but the relieving line don't get to use their pila.

[Patrick Waterson]

My impression is that line relief would have to be conducted, or at least conductible, in the heat of action, otherwise opponents would quickly learn that all you have to do is keep up the pressure and it cannot happen.

The relieving line could use their pila, shooting indirectly - and an overhead volley or two into the mass of the foe would create the kind of disruption that would help the engaged line to make a relatively keen break.

The two times we have line relief alluded to (Livy VIII.8 and Polybius II.33) it is described as 'retro cedentes' (retiring rearwards) and 'epi poda' (retiring backwards) respectively.  On the principle that in war one should keep things simple, perhaps the easiest explanation is that when the signal was given each file retired between the files of supporting troops, as Justin T suggests.

For this to be correct, the relieving line would have to be already drawn up for battle (i.e. no gaps between units).  Although absence of evidence is not necessarily evidence of absence, I have seen nothing to suggest that the relieving line started the relieving process with gaps unless we extrapolate from Scipio's unusual deployment at Zama.

Any more thoughts on this?

Patrick

[Justin Taylor]

I think it would have to be possible whilst in contact with the enemy. Otherwise no point in doing it. If you have to wait for the enemy to oblige then you may never get the chance.

[Justin Swanton]

Just remember it should be Roman legion, line relief continued in the Imperial armies as well.

Personally I go with the single file idea. The man of the new unit lets the men of the old unit go past him. Thus no one takes their eyes of the enemy and the whole tired unit is simply replaced in combat by the unit behind it.

Everything depends on this quote from Livy 8:8,5 "manipuli quindecim distantes inter se
modicum spatium manipulus levis vicenos milites", which Patrick brought up in this thread on the Arkaion Bellum blog: https://groups.google.com/forum/?hl=en&fromgroups=#!topic/arkaion-bellum/8kAvmeoXbcc

Here is the quoted line its context, using the Project Gutenberg translation, with the relevant line in bold:

The Romans formerly used targets; afterwards, when they began to receive pay, they made shields instead of targets; and what before constituted phalanxes similar to the Macedonian, afterwards became a line drawn up in distinct companies.

At length they were divided into several centuries. A century contained sixty soldiers, two centurions, and one standard-bearer. The spearmen (hastati) formed the first line in fifteen companies, with small intervals between them: a company had twenty light-armed soldiers, the rest wearing shields; those were called light who carried only a spear and short iron javelins. This, which constituted the van in the field of battle, contained the youth in early bloom advancing towards the age of service.

What we are looking at is two kinds of troops in the first line: 20 lightly armed soldiers armed with only a spear and javelins, and 40 more heavily armed troops equipped with shields. The context makes it fairly clear that there were small gaps between the fifteen companies (each company composed of the two troop types), and not between the two classes of troops in a company. A company by the way is a century.

Then follows the description of the rest of the legion:

'Next followed men of more robust age, in the same number of companies, who were called principes, all wearing shields, and distinguished by the completest armour. This band of thirty companies they called antepilani, because there were fifteen others placed behind them with the standards; of which each company consisted of three divisions, and the first division of each they called a pilus. Each company consisted of three ensigns, and contained one hundred and eighty-six men. The first ensign was at the head of the Triarii, veteran soldiers of tried bravery; the second, at the head of the Rorarii, men whose ability was less by reason of their age and course of service; the third, at the head of the Accensi, a body in whom very little confidence was reposed. For this reason also they were thrown[Pg 514] back to the rear.

So we are talking about another fifteen companies of Principes, who must have been spaced like the Hastati, i.e. with gaps between their companies.

Behind these were the third line, composed of Triarii, Rorarii and Accensi, forming a single company of 186 men, i.e. about 60 men of each type. This later on was compacted down to just the Triarii.

Now for the line relief:

When the army was marshalled according to this arrangement, the spearmen first commenced the fight. If the spearmen were unable to repulse the enemy, they retreated leisurely, and were received by the principes into the intervals of the ranks. The fight then devolved on the principes; the spearmen followed. The Triarii continued kneeling behind the ensigns, their left leg extended forward, holding their shields resting on their shoulders, and their spears fixed in the ground, with the points erect, so that their line bristled as if enclosed by a rampart.

'The intervals between the ranks' refers to the 'small intervals' mentioned earlier. This means that the front line troops didn't just filter through the files of the troops behind them, but between the gaps between one company and the next. 'The spearmen (Hastati) followed' must mean that they became the rear ranks of the Principes who, if they had originally been disposed in companies of 60 men would have logically been in blocks of 10 x 6 = a 10 deep line, becoming only 5 deep when the rear half of each file moved up to fill the gaps between the companies. An 8-man-deep line was the minimum practical depth for infantry in Antiquity. With the Hastati in support the Principes would become a line 10 men deep, quite sufficient for the task.

The same thing happened with the Principes if they did not prevail against the enemy:

If the principes also did not make sufficient impression in the fight, they retreated slowly from the front to the Triarii. Hence, when a difficulty is felt, "Matters have come to the Triarii," became a usual proverb. The Triarii rising up, after receiving the principes and spearmen into the intervals between their ranks, immediately closing their files, shut up as it were the openings; and in one compact body fell upon the enemy, no other hope being now left: that was the most formidable circumstance to the enemy, when having pursued them as vanquished, they beheld a new line suddenly starting up, increased also in strength.

The Triarii would have had rear support from the Rorarii and Accensii, forming, once the gaps were filled, a line 15 men deep, the greater depth necessary to counterbalance the poorer quality of the rear rank troops.

A refinement to my diagrams would be to have the Hastati gradually collapse into a series of half circles that shrink back towards the narrowing gaps between the Principes behind them. That way individual soldiers are not obliged to 'slide sideways' but can slowly retreat straight backwards until clear and safe through the lanes.

[Justin Taylor]

This means that the front line troops didn't just filter through the files of the troops behind them, but between the gaps between one company and the next.

Nope, it means exactly what it says, moving through the files would be perfectly acceptable.

The velites were not equipped as the rest of the legionaries and would have made poor battle-line troops. I think you will find that the numbers of velites were additional to the numbers of Hastati and that the numbers in maniples of Princepes and Hastati were the same. That the maniples of the Triarii were only half the strength of Hastati and Princepes.

I have always wondered why the weapons of the Triarii were different to the two previous lines, it seems a bit odd to ask people to change the weapons they were used to. I have two ideas; that the spears made a better defensive weapon and that they might need less agility to use (so more suitable for old men).

[Erpingham]

This means that the front line troops didn't just filter through the files of the troops behind them, but between the gaps between one company and the next.

Nope, it means exactly what it says, moving through the files would be perfectly acceptable.

<snip>

I have always wondered why the weapons of the Triarii were different to the two previous lines, it seems a bit odd to ask people to change the weapons they were used to. I have two ideas; that the spears made a better defensive weapon and that they might need less agility to use (so more suitable for old men).

To get the exact meaning of what the intervals are between you need to look at the Latin.  My Latin is dreadful, but if I ask Patrick nicely, he may oblige

On the spears of the Triarii, I think you are probably right. The pilum was an offensive weapon and the triarii are a defensive reserve, so perhaps the spear better fitted the tactics expected of them.

[Patrick Waterson]

*dusts off book cover and clears throat*

The key bit is when, the hastati being unable to overcome the enemy (i.e. things are happening the other way around) the hastati begin, in VIII.8.9:

"... pede presso eos retro cedentes in intervalla ordinum principes recipiebant"

'Pede presso' has the sense of being closely pressed, suggesting this is done in the heat of action.  'Eos' is the pronoun for the hastati and 'retro cedentes' means retreating rearwards or (most probably) backwards.  Hence:

"Step by step, retreating backwards ..."

'In intervalla ordinum' is one of those expressions that is very open to translation.  'Principes recipiebant' simply means: 'The principes received them' and the use of the imperfect tense suggests a process that went on for a little while rather than being executed in the blink of an eye.

The principes received the hastati into the 'intervalla ordinum', the intervals between their 'ordines' (literally the intervals of their 'ordines'.  Previously in the passage in question Livy has used 'ordo' (plural 'ordines') to mean 'formations'.  However the word had multiple uses, and is often understood and translated as 'ranks' ('row, line, series, order, rank') - this to me seems a misconception, as the building blocks of classical armies were not ranks but files.  Hence I would understand 'intervalla ordinum' as 'through the gaps between the files'.  If 'ordines' should despite my preconceptions actually mean 'ranks', then the hastati are being received into the gaps in the ranks, i.e. the modest lateral spatial allowance between men.  The result is the same.

Understood this way, the passage would support the idea of files of hastati passing backwards between files of principes.  It would be a fairly tight fit, but not an impossible one, and would allow handover as soon as the fighting rank of hastati dropped back past the first rank of principes, who would probably introduce themselves to an opponent wondering which of his two foes to go for with a solid shield push and a swordthrust to the unmentionables.

That is one understanding.

If on the other hand we interpret 'in intervalla ordinum' as 'through the intervals between the formations', which has the advantage of keeping Livy's usage of 'ordo' consistent, we need to envisage a mechanism by which the first line could insert itself toothpaste-link into these gaps and the second line squeeze from a collection of separate groupings into a single cohesive line while this was happening.  This has been the traditional interpretation and focus of the passage, and I think Justin Swanton's ingenious proposal comes as close as one can to devising an approach that meets these seemingly impossible requirements.  If there is a better explanation under these parameters I have yet to see it.

That said, were I training a Roman army, I would have the first-line files back between the second-line files for battlefield relief.  Much less could go wrong that way.

The triarii have an interesting history.  Back in 509 BC they are veterans acting as camp guards.  They are still doing this c.437 BC.  By 394 BC they are deployed as the third line of the army.  By 340 BC their battle procedures are described by Livy in VIII.8.10-12:

"The triarii knelt beneath their banners, with the left leg advanced, having their shields leaning against their shoulders and their spears thrust into the ground and pointing obliquely upwards, as if their battle-line were fortified with a bristling palisade. [11] if the principes, too, were unsuccessful in their fight, they fell back slowly from the battle-line on the triarii. (From this arose the adage, "to have come to the triarii," when things are going badly.) [12] The triarii, rising up after they had received the principes and hastati into the intervals between their companies [in intervalla ordinum, 'formations', 'ranks' or 'files'], would at once draw their companies together [extemplo compressis ordinibus, probably 'files'] and close the lanes, as it were [velut claudebant vias]; then, with no more reserves behind to count on, they would charge the enemy in one compact array [uno continente agmine]."

Livy's use of 'vias' (way, road, passage) and his reference to the triarii closing up ('compressis ordinibus' = 'with files - or formations - close together') and charging the enemy in a single cohesive block makes one wonder if the triarii initially deployed in double depth but on a 6' per man frontage, the reason being that if they deployed on the usual 3' frontage then their obliquely upward-pointing spears could make life very difficult for friends trying to retreat between them (a case of 'friendly-don't-like-it-up-'em syndrome').  It is a lot quicker and easier for a double-depth open formation to become a single-depth closed formation than for a collection of subunits to form a single coherent line the moment friends have finished passing through them.  The retention of hoplite-style armament for triarii perhaps reflects the greater effectiveness of a hoplite-style charge compared to a pilum-and-gladius slog as a battle-finisher, and its retention for a time when foes would have run out of missile weapons perhaps suggests that it would not have fared so well against a pilum volley immediately followed by a clash against an intact formed opponent.  These are conjectures.  Livy does however describe the appearance of the triarii and their immediate onset as "formidolosissimum", which is about as great a degree of panic-inducing dread as Latin will allow.

Patrick

[Justin Swanton]

Looking at the Latin of this passage, Livy uses 'ordo' and 'manipulum' interchangeably. I see no implication that 'ordo' is used in the sense of 'files'. For example:

[7] hoc triginta manipulorum agmen antepilanos appellabant, quia sub signis iam alii quindecim ordines locabantur,

[7] this body of thirty maniples they called antepilani, because behind the standards there were again stationed other fifteen companies

To my mind it would rather force the text to translate 'ordo' by 'file'.

Having said that I am very Shakespearean when it comes to Latin (and more so with Greek) 

[Patrick Waterson]

Justin, you are absolutely correct in this instance. 

However the part that needs explaining is: 'in intervalla ordinum principes recipiebant', and here we have to be fussy because, as you correctly point out, the principes and hastati have been described as being in 'manipuli' whereas the triarii, rorarii and accensi are in 'ordines'.  Hence if maniples of hastati are filtering between maniples of principes we should be seeing:

'inter intervalla manipulorum principes recipiebant'
(The principes received them between the spaces of their maniples.)

whereas we have:

'in intervalla ordinum principes recipiebant'. 
(The principes received them into the spaces of their ordines.)

As the principes are not formed in 'ordo' subunits but in 'manipulus' subunits, 'ordo' here must mean something other than a 60-man subunit, and one would expect the usual meaning of 'ranks' or (as I believe may be the case) 'files'.

Patrick
P.S. - I should mention that a 'manipulus' seems to have been 80-strong while an 'ordo' was 60.

[Edit:] P.P.S. - I should also mention that the 60-man formation is a 'vexillum' and three 'vexilla' (one each of triarii, rorarii and accensi) constitute a 186-man (including officers) 'ordo'.  Mea culpa, and thanks to Justin Swanton for diplomaticaly pointing this out.

[Erpingham]

P.S. - I should mention that a 'manipulus' seems to have been 80-strong while an 'ordo' was 60.

Is that specific to this passage?  I thought a maniple was two centuries, a prior and a posterior?    Shouldn't it therefore be 160 strong? 

[Justin Swanton]

However the part that needs explaining is: 'in intervalla ordinum principes recipiebant', and here we have to be fussy because, as you correctly point out, the principes and hastati have been described as being in 'manipuli' whereas the triarii, rorarii and accensi are in 'ordines'.  Hence if maniples of hastati are filtering between maniples of principes we should be seeing:

'inter intervalla manipulorum principes recipiebant'
(The principes received them between the spaces of their maniples.)

whereas we have:

'in intervalla ordinum principes recipiebant'. 
(The principes received them into the spaces of their ordines.)

As the principes are not formed in 'ordo' subunits but in 'manipulus' subunits, 'ordo' here must mean something other than a 60-man subunit, and one would expect the usual meaning of 'ranks' or (as I believe may be the case) 'files'.

Reading Livy, it is clear - as you have pointed out - that 'ordo' is a generic term meaning a body of men of any size. 'Manipulum' is more precise and means a body of men of a certain size - 62 (or 80) in this case. 'Company' can be used to designate a maniple. Livy's reason for doing this could have been literary, a preference for using different terms to avoid the language becoming too monotone.

In context, 'ordo' here is used to designate the larger Triarii body or, in one instance, the smaller manipular body. The link that Livy makes between '15 companies' and '15 maniples' just makes me think that suddenly using 'company' to indicate a much smaller file unit - without him making it clear that he is doing so - would strain the meaning of the word as used here.

P.S. - I should mention that a 'manipulus' seems to have been 80-strong while an 'ordo' was 60.

OK, doing the maths:

Triarii, Rorarii, Accensii: 15 x 186 = 2790
Principes, Hastati: 15 x 2 x 62 = 1860

Total: 4650 men

Triarii, Rorarii, Accensii: 15 x 186 = 2790
Principes, Hastati: 15 x 2 x 80 = 2400

Total: 4650 men = 5190 men

Which is closer to Livy's total estimate for the size of a legion. Or am I missing something?

One question: would the maniples have been organised as 10 men wide and 8 deep or 8 men wide and 10 deep? I'm thinking the former but just checking.

[Patrick Waterson]

P.S. - I should mention that a 'manipulus' seems to have been 80-strong while an 'ordo' was 60.

Is that specific to this passage?  I thought a maniple was two centuries, a prior and a posterior?    Shouldn't it therefore be 160 strong? 

Not yet - as far as I can establish, the 'century' as a legionary subunit does not appear before c.311 BC, the putative date for the change from the 'Livian' legion of Livy VIII.8 with its fifteen maniples per line and four lines (five if accensi are fielded) to the 'Polybian' legion with ten stronger maniples per line (each of two 'centuries') and only three lines.

The Livian maniple was 80 men for the hastati and principes (hastati has 60 heavy and 20 light troops, principes 80 heavy troops).  The 60-man triarii/rorarii/accensi maniple was called the 'ordo'.

The Polybian maniple for hastati and principes had 160 men at normal strength and 200 at emergency strength.  It was divided into two 'centuries', and at emergency strength a 'century' was exactly 100 men, hence the term.  The maniple contained 40 velites with the balance being heavy troops.

Polybian triarii were organised in ten 100-man maniples.  These each consisted of 40 velites and 60 triarii proper and, like the hastati and principes maniples, each had two centurions (Polybius VI.24).  We can infer that triarii maniples in the Polybian legion were formed into half-strength centuries.

Much confusion has arisen from attempts to read Polybian structures back into the Livian legion.  In particular, the century is Polybian.  It is not mentioned as part of the Livian legion.

Hope that clarifies the matter.

Patrick

[Patrick Waterson]

OK, doing the maths:

Triarii, Rorarii, Accensii: 15 x 186 = 2790
Principes, Hastati: 15 x 2 x 62 = 1860

Total: 4650 men

Triarii, Rorarii, Accensii: 15 x 186 = 2790
Principes, Hastati: 15 x 2 x 80 = 2400

Total: 4650 men = 5190 men

Which is closer to Livy's total estimate for the size of a legion. Or am I missing something?

One question: would the maniples have been organised as 10 men wide and 8 deep or 8 men wide and 10 deep? I'm thinking the former but just checking.

Livy gives the size of the 340 BC legion as 5,000 men ("There were usually four legions enlisted, with 5,000 men and 300 horse to each legion." - Livy VIII.8 ).

This would appear to be the emergency strength: elsewhere the legion infantry strength for this period (4th century BC) is given as c.4,000 or 4,200 men, a figure attained by simply not enlisting the accensi, who seem to have been emergency levies only.

The Livian maniple would have been 10 wide and 8 deep (triarii etc. 10 wide and 6 deep).

'Company' can be used to designate a maniple. Livy's reason for doing this could have been literary, a preference for using different terms to avoid the language becoming too monotone.

Ahem - Livy uses 'manipulus' and 'ordo' - and 'vexillum' for a grouping of three 'ordo' formations.  He does not use 'company'.  Only a translator into English can use 'company' to designate a maniple.