10-11-2011, 06:50 PM
As I hope is till now clear, I do support that in antiquity and Byzantine period, intervals between infantry units, even those of the first line, could be employed. It is the width of these, their function and nature that I contest. In my opinion, the Romans of the periods in question did not deploy in maniple or later cohort sized units with intervals between each other equal to their width. Again I do agree that intervals would have been employed as suggested before combat or by the rear lines but I disagree with their use during the actual melee. Until now I have not specifically occupied myself in these posts with how the Roman system actually worked, I have only contested the existence of these intervals.
Indeed, there are mentions of such intervals in their primary sources, unfortunately very few determine their width and none actually explaining or describing their use in combat. No mention of any such interval being exploited by the enemy (in the specified era) exists, nor any mention of any measure as to how to guard it. Of course lack of such evidence is not proof, this is why the debate rages even today, thus while not denying the probability I will show quotes that suggests that such intervals were not employed.
Polybius may be our best source. He makes mistakes but all in all, he is a source to trust and respect and deserves very careful study. He was knowledgeable in the art of war, so his words carry weight. It is true that Polybius mentions intervals both at Zama and Cannae. About the first battle (15.9.6.), he also mentions that the maniples of the principes were traditionally posted behind the intervals between the maniples of the hastati. The text is very straightforward, but nowhere does it say that these intervals would be retained during the melee against Hannibal’s lines. One could of course contest that it also nowhere says that they were somehow closed and he would of course be right. The reasons why such a formation would have been used before melee is evident to all. It facilitated the maneuvers of cavalry and light infantry, made actual marching easier by enabling maniples to march around certain obstacles. Greek armies tried to address the same issues by marching in open order (6 feet per man), which they called “natural”.
The Greek text reads :
“ὁ μὲν Πόπλιος ἔθηκε τὰς τάξεις τῶν ἰδίων δυνάμεων τὸν τρόπον τοῦτον. [7] πρῶτον μὲν τοὺς ἁστάτους καὶ τὰς τούτων σημαίας ἐν διαστήμασιν, ἐπὶ δὲ τούτοις τοὺς πρίγκιπας, τιθεὶς τὰς σπείρας οὐ κατὰ τὸ τῶν πρώτων σημαιῶν διάστημα, καθάπερ ἔθος ἐστὶ τοῖς Ῥωμαίοις, ἀλλὰ καταλλήλους ἐν ἀποστάσει διὰ τὸ πλῆθος τῶν παρὰ τοῖς ἐναντίοις ἐλεφάντων: τελευταίους δ᾽ ἐπέστησε τοὺς τριαρίους. [8] ἐπὶ δὲ τῶν κεράτων ἔταξε κατὰ μὲν τὸ λαιὸν Γάιον Λαίλιον, ἔχοντα τοὺς Ἰταλικοὺς ἱππέας, κατὰ δὲ τὸ δεξιὸν μέρος Μασαννάσαν μετὰ πάντων τῶν ὑφ᾽ ἑαυτὸν ταττομένων Νομάδων. [9] τὰ δὲ διαστήματα τῶν πρώτων σημαιῶν ἀνεπλήρωσε ταῖς τῶν γροσφομάχων σπείραις, παραγγείλας τούτοις προκινδυνεύειν, [10] ἐὰν δ᾽ ἐκβιάζωνται κατὰ τὴν τῶν θηρίων ἔφοδον, ἀποχωρεῖν, τοὺς μὲν καταταχοῦντας διὰ τῶν ἐπ᾽ εὐθείας διαστημάτων εἰς τοὐπίσω τῆς ὅλης δυνάμεως, τοὺς δὲ περικαταλαμβανομένους εἰς τὰ πλάγια παρίστασθαι διαστήματα κατὰ τὰς σημαίας.”
I only give this text to just give the information that Polybius never uses the term “maniple” in his text, this is the Roman term we use to translate the Greek terms he uses. It is only interesting when coupled with :
“τοῦτο δὲ καλεῖται τὸ σύνταγμα τῶν πεζῶν παρὰ Ῥωμαίοις κοόρτις”, Pol.11.23.1
“That unit of infantry is called by the Romans a cohort”.
I am digressing but I thought it interesting to include in this post since many are very interested in the history of the usage of military terms. By no means do I contest that the word “maniple” is wrong or something!
In the same battle Polybius says :
“Thus it came about that their charge threw the maniples of the hastati into confusion; whereupon the officers of the principes caused their lines to advance to oppose them.” 15.13.7.
“καὶ δὴ τῷ τοιούτῳ τρόπῳ συνέχεαν ἐπιπεσόντες τὰς τῶν ἁστάτων σημαίας: οἱ μέντοι τῶν πριγκίπων ἡγεμόνες συνθεασάμενοι τὸ γεγονὸς ἐπέστησαν τὰς αὑτῶν τάξεις.”
This has nothing to do with the existence of the intervals but it shows that, at least according to Polybius, the principes did not alternately attack the enemy line (like pistons). They indeed ran to the support of the faltering hastati. The translation is not exactly correct but the general meaning is indeed the same. Is the “piston” attack model (If I understood it correctly) required in your model Bryan to make sense of the intervals?
And then Polybius says :
“and the hastati to be recalled from the pursuit by the sound of a bugle, and drew them up where they were in advance of the ground on which the fighting had taken place, opposite the enemy's center. He then ordered the principes and triarii to take close order, and, threading their way through the corpses, to deploy into line with the hastati on either flank. When they had surmounted the obstacles and got into line with the hastati, the two lines charged each other with the greatest fire and fury.” 15.14.3
“τοὺς δ᾽ ἐπιδιώκοντας τῶν ἁστάτων ἀνακαλεσάμενος διὰ τῆς σάλπιγγος, τοὺς μὲν αὐτοῦ πρὸ τῆς μάχης κατὰ μέσους τοὺς πολεμίους ἐπέστησε, [4] τοὺς δὲ πρίγκιπας καὶ τριαρίους πυκνώσας ἐφ᾽ ἑκάτερον τὸ κέρας προάγειν παρήγγειλε διὰ τῶν νεκρῶν. [5] ἐπειδὴ δ᾽ ὑπερβάντες ἐξ ἴσου τοῖς ἁστάτοις ἐγένοντο, συνέβαλον αἱ φάλαγγες ἀλλήλαις μετὰ τῆς μεγίστης ὁρμῆς καὶ προθυμίας.”
By reading the English text we may find a certain obscure point : he says that “the Principes and Triarii took close order and deployed into line on each of the hastati flank and in line with them.” We might ask ourselves what this closing of order is. Up until now they would have been deployed in the same order the Hastati were. So how would they close up? The Greek text indeed says so but what is not readily understood in the translation is that it also says : “the two phalanxes engaged…”. The word is given as “line” in the translation. In my opinion, this quote would only make sense if the maniples of the Principes and the Triarii closed up the maniples (not the men), formed a single phalanx with the Hastati (that meaning that the Hastati also fought in a single line) and then engaged… Any alternative explanations anyone?
In his description of Cannae, Polybius indeed says :
“and their foot next them in the same line, placing the maniples, however, closer together than usual, and making the depth of each maniple several times greater than its front.” 3.113.3
“τοὺς δὲ πεζοὺς συνεχεῖς τούτοις ἐπὶ τῆς αὐτῆς εὐθείας ἐξέτεινε, πυκνοτέρας ἢ πρόσθεν τὰς σημείας καθιστάνων, καὶ ποιῶν πολλαπλάσιον τὸ βάθος ἐν ταῖς σπείραις τοῦ μετώπου”
Again, the meaning is practically the same with small “errors”.
(Actually the translation reads : “the infantry he posted at an even front (with the cavalry), making the maniples denser than before and the depth of the maniples several times greater than their front.” This makes us wonder if the maniples were arrayed with smaller intervals or if the men in the maniples were arrayed in closer order. I tend to agree that he talks about the intervals here, but one could indeed contest that.).
Yet, the “fighting with intervals” theory is contested by the next quote in the same battle description :
“Still they fought, though no longer in line, yet singly, or in maniples, which faced about to meet those who charged them on the flanks.”, Pol.3.115.12
Again it is not that evident until we read the Greek text :
“οὗτοι μὲν οὖν οὐκέτι φαλαγγηδόν, ἀλλὰ κατ᾽ ἄνδρα καὶ κατὰ σπείρας στρεφόμενοι πρὸς τοὺς ἐκ τῶν πλαγίων”
We tend to read “line” and think of a general battle line. But here we have three different modes of fighting clearly expressed by Polybius!
“they fought not like a phalanx, but as single men or as maniples…”
So, fighting in maniples was not the way they fought before disorder came…
Vegetius is a later resource and not the most trustworthy one too, but he is also quite clear when he explains how the space required for the arrangement of a line should be calculated. In his third book, the appropriate chapter says :
“PROPER DISTANCES AND INTERVALS
Having explained the general disposition of the lines, we now come to the distances and dimensions. One thousand paces contain a single rank of one thousand six hundred and fifty-six foot soldiers, each man being allowed three feet. Six ranks drawn up on the same extent of ground will require nine thousand nine hundred and ninety-six men. To form only three ranks of the same number will take up two thousand paces, but it is much better to increase the number of ranks than to make your front too extensive. We have before observed the distance between each rank should be six feet, one foot of which is taken up by the men. Thus if you form a body of ten thousand men into six ranks they will occupy thirty-six feet. in depth and a thousand paces in front. By this calculation it is easy to compute the extent of ground required for twenty or thirty thousand men to form upon. Nor can a general be mistaken when thus he knows the proportion of ground for any fixed number of men.
But if the field of battle is not spacious enough or your troops are very numerous, you may form them into nine ranks or even more, for it is more advantageous to engage in close order that to extend your line too much. An army that takes up too much ground in front and too little in depth, is quickly penetrated by the enemy's first onset. After this there is no remedy. As to the post of the different corps in the right or left wing or in the center, it is the general rule to draw them up according to their respective ranks or to distribute them as circumstances or the dispositions of the enemy may require.”
Another interesting chapter is :
“RESERVES
The method of having bodies of reserves in rear of the army, composed of choice infantry and cavalry, commanded by the supernumerary lieutenant generals, counts and tribunes, is very judicious and of great consequence towards the gaining of a battle. Some should be posted in rear of the wings and some near the center, to be ready to fly immediately to the assistance of any part of the line which is hard pressed, to prevent its being pierced, to supply the vacancies made therein during the action and thereby to keep up the courage of their fellow soldiers and check the impetuosity of the enemy. This was an invention of the Lacedaemonians, in which they were imitated by the Carthaginians. The Romans have since observed it, and indeed no better disposition can be found.
The line is solely designed to repulse, or if possible, break the enemy. If it is necessary to form the wedge or the pincers, it must be done by the supernumerary troops stationed in the rear for that purpose. If the saw is to be formed, it must also be done from the reserves, for if once you begin to draw off men from the line you throw all into confusion. If any flying platoon of the enemy should fall upon your wing or any other part of your army, and you have no supernumerary troops to oppose it or if you pretend to detach either horse or foot from your line for that service by endeavoring to protect one part, you will expose the other to greater danger. In armies not very numerous, it is much better to contract the front, and to have strong reserves. In short, you must have a reserve of good and well-armed infantry near the center to form the wedge and thereby pierce the enemy's line; and also bodies of cavalry armed with lances and cuirasses, with light infantry, near the wings, to surround the flanks of the enemy.”
He definitely does not allow the formation of sizable intervals and the role of the second line is to support and not actively fight unless becoming part of the actual line by forming the pincers or the wedge in front of the first line and, as I understand, joining it. Vegetius is trying to give information and advice that, in his mind, reflects reality in the eras we are interested in, so, these chapters are important to at least understand how lettered men of his time understood Roman fighting of the eras in question.
I have to leave in a few minutes, so I will only add some quotes by Frontinus for the time being. Frontinus is very close to the era in question and he is certainly more reliable than Vegetius. He says in his second book, in the third chapter called “On the Disposition of Troops for Battle”:
“Against this formation Scipio drew up the flower of his legions in three successive front lines, arranged according to hastati, principes, and triarii, not making the cohorts touch, but leaving a space between the detached companies through which the elephants driven by the enemy might easily be allowed to pass without throwing the ranks into confusion. These intervals he filled with light-armed skirmishers, that the line might show no gaps, giving them instructions to withdraw to the rear or the flanks at the first onset of the elephants.”, 2.3.16
If translated correctly, this text is very informative as to how Frontinus made sense of the same things discussed above about the battle of Zama. He thinks that Scipio’s leaving the intervals was a stratagem to counter the anticipated offensive of the elephants and that in his opinion the maniples should touch. The reason why the intervals were filled with velites was that the line should show no gaps. So, at least in Frontinus time and of course knowledge, the cohosrt would touch and the line was deemed important to show no gaps (this is also mentioned in later Byzantine manuals as to how to form such intervals) . At least to Frontinus, it was important that the enemy saw no gaps.
In 2.3.17, Frotinus presents another instance in which Sulla formed intervals to be able to send in ligt infantry and cavalry to counter the war chariots of Archelaus.
In 2.3.18, he says that in this way Julius Caesar countered the scythe bearing chariots of the Gauls.
I will continue when I come home…
Indeed, there are mentions of such intervals in their primary sources, unfortunately very few determine their width and none actually explaining or describing their use in combat. No mention of any such interval being exploited by the enemy (in the specified era) exists, nor any mention of any measure as to how to guard it. Of course lack of such evidence is not proof, this is why the debate rages even today, thus while not denying the probability I will show quotes that suggests that such intervals were not employed.
Polybius may be our best source. He makes mistakes but all in all, he is a source to trust and respect and deserves very careful study. He was knowledgeable in the art of war, so his words carry weight. It is true that Polybius mentions intervals both at Zama and Cannae. About the first battle (15.9.6.), he also mentions that the maniples of the principes were traditionally posted behind the intervals between the maniples of the hastati. The text is very straightforward, but nowhere does it say that these intervals would be retained during the melee against Hannibal’s lines. One could of course contest that it also nowhere says that they were somehow closed and he would of course be right. The reasons why such a formation would have been used before melee is evident to all. It facilitated the maneuvers of cavalry and light infantry, made actual marching easier by enabling maniples to march around certain obstacles. Greek armies tried to address the same issues by marching in open order (6 feet per man), which they called “natural”.
The Greek text reads :
“ὁ μὲν Πόπλιος ἔθηκε τὰς τάξεις τῶν ἰδίων δυνάμεων τὸν τρόπον τοῦτον. [7] πρῶτον μὲν τοὺς ἁστάτους καὶ τὰς τούτων σημαίας ἐν διαστήμασιν, ἐπὶ δὲ τούτοις τοὺς πρίγκιπας, τιθεὶς τὰς σπείρας οὐ κατὰ τὸ τῶν πρώτων σημαιῶν διάστημα, καθάπερ ἔθος ἐστὶ τοῖς Ῥωμαίοις, ἀλλὰ καταλλήλους ἐν ἀποστάσει διὰ τὸ πλῆθος τῶν παρὰ τοῖς ἐναντίοις ἐλεφάντων: τελευταίους δ᾽ ἐπέστησε τοὺς τριαρίους. [8] ἐπὶ δὲ τῶν κεράτων ἔταξε κατὰ μὲν τὸ λαιὸν Γάιον Λαίλιον, ἔχοντα τοὺς Ἰταλικοὺς ἱππέας, κατὰ δὲ τὸ δεξιὸν μέρος Μασαννάσαν μετὰ πάντων τῶν ὑφ᾽ ἑαυτὸν ταττομένων Νομάδων. [9] τὰ δὲ διαστήματα τῶν πρώτων σημαιῶν ἀνεπλήρωσε ταῖς τῶν γροσφομάχων σπείραις, παραγγείλας τούτοις προκινδυνεύειν, [10] ἐὰν δ᾽ ἐκβιάζωνται κατὰ τὴν τῶν θηρίων ἔφοδον, ἀποχωρεῖν, τοὺς μὲν καταταχοῦντας διὰ τῶν ἐπ᾽ εὐθείας διαστημάτων εἰς τοὐπίσω τῆς ὅλης δυνάμεως, τοὺς δὲ περικαταλαμβανομένους εἰς τὰ πλάγια παρίστασθαι διαστήματα κατὰ τὰς σημαίας.”
I only give this text to just give the information that Polybius never uses the term “maniple” in his text, this is the Roman term we use to translate the Greek terms he uses. It is only interesting when coupled with :
“τοῦτο δὲ καλεῖται τὸ σύνταγμα τῶν πεζῶν παρὰ Ῥωμαίοις κοόρτις”, Pol.11.23.1
“That unit of infantry is called by the Romans a cohort”.
I am digressing but I thought it interesting to include in this post since many are very interested in the history of the usage of military terms. By no means do I contest that the word “maniple” is wrong or something!
In the same battle Polybius says :
“Thus it came about that their charge threw the maniples of the hastati into confusion; whereupon the officers of the principes caused their lines to advance to oppose them.” 15.13.7.
“καὶ δὴ τῷ τοιούτῳ τρόπῳ συνέχεαν ἐπιπεσόντες τὰς τῶν ἁστάτων σημαίας: οἱ μέντοι τῶν πριγκίπων ἡγεμόνες συνθεασάμενοι τὸ γεγονὸς ἐπέστησαν τὰς αὑτῶν τάξεις.”
This has nothing to do with the existence of the intervals but it shows that, at least according to Polybius, the principes did not alternately attack the enemy line (like pistons). They indeed ran to the support of the faltering hastati. The translation is not exactly correct but the general meaning is indeed the same. Is the “piston” attack model (If I understood it correctly) required in your model Bryan to make sense of the intervals?
And then Polybius says :
“and the hastati to be recalled from the pursuit by the sound of a bugle, and drew them up where they were in advance of the ground on which the fighting had taken place, opposite the enemy's center. He then ordered the principes and triarii to take close order, and, threading their way through the corpses, to deploy into line with the hastati on either flank. When they had surmounted the obstacles and got into line with the hastati, the two lines charged each other with the greatest fire and fury.” 15.14.3
“τοὺς δ᾽ ἐπιδιώκοντας τῶν ἁστάτων ἀνακαλεσάμενος διὰ τῆς σάλπιγγος, τοὺς μὲν αὐτοῦ πρὸ τῆς μάχης κατὰ μέσους τοὺς πολεμίους ἐπέστησε, [4] τοὺς δὲ πρίγκιπας καὶ τριαρίους πυκνώσας ἐφ᾽ ἑκάτερον τὸ κέρας προάγειν παρήγγειλε διὰ τῶν νεκρῶν. [5] ἐπειδὴ δ᾽ ὑπερβάντες ἐξ ἴσου τοῖς ἁστάτοις ἐγένοντο, συνέβαλον αἱ φάλαγγες ἀλλήλαις μετὰ τῆς μεγίστης ὁρμῆς καὶ προθυμίας.”
By reading the English text we may find a certain obscure point : he says that “the Principes and Triarii took close order and deployed into line on each of the hastati flank and in line with them.” We might ask ourselves what this closing of order is. Up until now they would have been deployed in the same order the Hastati were. So how would they close up? The Greek text indeed says so but what is not readily understood in the translation is that it also says : “the two phalanxes engaged…”. The word is given as “line” in the translation. In my opinion, this quote would only make sense if the maniples of the Principes and the Triarii closed up the maniples (not the men), formed a single phalanx with the Hastati (that meaning that the Hastati also fought in a single line) and then engaged… Any alternative explanations anyone?
In his description of Cannae, Polybius indeed says :
“and their foot next them in the same line, placing the maniples, however, closer together than usual, and making the depth of each maniple several times greater than its front.” 3.113.3
“τοὺς δὲ πεζοὺς συνεχεῖς τούτοις ἐπὶ τῆς αὐτῆς εὐθείας ἐξέτεινε, πυκνοτέρας ἢ πρόσθεν τὰς σημείας καθιστάνων, καὶ ποιῶν πολλαπλάσιον τὸ βάθος ἐν ταῖς σπείραις τοῦ μετώπου”
Again, the meaning is practically the same with small “errors”.
(Actually the translation reads : “the infantry he posted at an even front (with the cavalry), making the maniples denser than before and the depth of the maniples several times greater than their front.” This makes us wonder if the maniples were arrayed with smaller intervals or if the men in the maniples were arrayed in closer order. I tend to agree that he talks about the intervals here, but one could indeed contest that.).
Yet, the “fighting with intervals” theory is contested by the next quote in the same battle description :
“Still they fought, though no longer in line, yet singly, or in maniples, which faced about to meet those who charged them on the flanks.”, Pol.3.115.12
Again it is not that evident until we read the Greek text :
“οὗτοι μὲν οὖν οὐκέτι φαλαγγηδόν, ἀλλὰ κατ᾽ ἄνδρα καὶ κατὰ σπείρας στρεφόμενοι πρὸς τοὺς ἐκ τῶν πλαγίων”
We tend to read “line” and think of a general battle line. But here we have three different modes of fighting clearly expressed by Polybius!
“they fought not like a phalanx, but as single men or as maniples…”
So, fighting in maniples was not the way they fought before disorder came…
Vegetius is a later resource and not the most trustworthy one too, but he is also quite clear when he explains how the space required for the arrangement of a line should be calculated. In his third book, the appropriate chapter says :
“PROPER DISTANCES AND INTERVALS
Having explained the general disposition of the lines, we now come to the distances and dimensions. One thousand paces contain a single rank of one thousand six hundred and fifty-six foot soldiers, each man being allowed three feet. Six ranks drawn up on the same extent of ground will require nine thousand nine hundred and ninety-six men. To form only three ranks of the same number will take up two thousand paces, but it is much better to increase the number of ranks than to make your front too extensive. We have before observed the distance between each rank should be six feet, one foot of which is taken up by the men. Thus if you form a body of ten thousand men into six ranks they will occupy thirty-six feet. in depth and a thousand paces in front. By this calculation it is easy to compute the extent of ground required for twenty or thirty thousand men to form upon. Nor can a general be mistaken when thus he knows the proportion of ground for any fixed number of men.
But if the field of battle is not spacious enough or your troops are very numerous, you may form them into nine ranks or even more, for it is more advantageous to engage in close order that to extend your line too much. An army that takes up too much ground in front and too little in depth, is quickly penetrated by the enemy's first onset. After this there is no remedy. As to the post of the different corps in the right or left wing or in the center, it is the general rule to draw them up according to their respective ranks or to distribute them as circumstances or the dispositions of the enemy may require.”
Another interesting chapter is :
“RESERVES
The method of having bodies of reserves in rear of the army, composed of choice infantry and cavalry, commanded by the supernumerary lieutenant generals, counts and tribunes, is very judicious and of great consequence towards the gaining of a battle. Some should be posted in rear of the wings and some near the center, to be ready to fly immediately to the assistance of any part of the line which is hard pressed, to prevent its being pierced, to supply the vacancies made therein during the action and thereby to keep up the courage of their fellow soldiers and check the impetuosity of the enemy. This was an invention of the Lacedaemonians, in which they were imitated by the Carthaginians. The Romans have since observed it, and indeed no better disposition can be found.
The line is solely designed to repulse, or if possible, break the enemy. If it is necessary to form the wedge or the pincers, it must be done by the supernumerary troops stationed in the rear for that purpose. If the saw is to be formed, it must also be done from the reserves, for if once you begin to draw off men from the line you throw all into confusion. If any flying platoon of the enemy should fall upon your wing or any other part of your army, and you have no supernumerary troops to oppose it or if you pretend to detach either horse or foot from your line for that service by endeavoring to protect one part, you will expose the other to greater danger. In armies not very numerous, it is much better to contract the front, and to have strong reserves. In short, you must have a reserve of good and well-armed infantry near the center to form the wedge and thereby pierce the enemy's line; and also bodies of cavalry armed with lances and cuirasses, with light infantry, near the wings, to surround the flanks of the enemy.”
He definitely does not allow the formation of sizable intervals and the role of the second line is to support and not actively fight unless becoming part of the actual line by forming the pincers or the wedge in front of the first line and, as I understand, joining it. Vegetius is trying to give information and advice that, in his mind, reflects reality in the eras we are interested in, so, these chapters are important to at least understand how lettered men of his time understood Roman fighting of the eras in question.
I have to leave in a few minutes, so I will only add some quotes by Frontinus for the time being. Frontinus is very close to the era in question and he is certainly more reliable than Vegetius. He says in his second book, in the third chapter called “On the Disposition of Troops for Battle”:
“Against this formation Scipio drew up the flower of his legions in three successive front lines, arranged according to hastati, principes, and triarii, not making the cohorts touch, but leaving a space between the detached companies through which the elephants driven by the enemy might easily be allowed to pass without throwing the ranks into confusion. These intervals he filled with light-armed skirmishers, that the line might show no gaps, giving them instructions to withdraw to the rear or the flanks at the first onset of the elephants.”, 2.3.16
If translated correctly, this text is very informative as to how Frontinus made sense of the same things discussed above about the battle of Zama. He thinks that Scipio’s leaving the intervals was a stratagem to counter the anticipated offensive of the elephants and that in his opinion the maniples should touch. The reason why the intervals were filled with velites was that the line should show no gaps. So, at least in Frontinus time and of course knowledge, the cohosrt would touch and the line was deemed important to show no gaps (this is also mentioned in later Byzantine manuals as to how to form such intervals) . At least to Frontinus, it was important that the enemy saw no gaps.
In 2.3.17, Frotinus presents another instance in which Sulla formed intervals to be able to send in ligt infantry and cavalry to counter the war chariots of Archelaus.
In 2.3.18, he says that in this way Julius Caesar countered the scythe bearing chariots of the Gauls.
I will continue when I come home…
