Depth - what is it good for?

[Erpingham]

This thread has been provoked by the discussions on columns in battle.  That discussion has concentrated on the march column but it did bring up the fact that in antiquity and the Middle Ages, armies occassionally fielded very deep formations, either rectalinear or triangular.

These armies clearly felt there was advantage in doing this.  What was it, and how do we best model it on the tabletop?

As a starter, I'll throw out a few theories I've read in various places

Weight - either literally pushing or creating a momentum/inertia effect.
Psychology - place more shaky troops in the middle of a dense block so they feel safer and supported
Command/control/manoeuver - put less skilled or experienced men in the middle and use experienced/trained men front and rear to make the whole thing handleable

The last two in particular seem influenced by 19th century views.

So, what is going on and how do reflect it?

[Justin Swanton]

Just throwing one or two ideas on the table.

Melee combat between infantry seems broadly to be of two kinds:

The first, best represented by swordfighting though not limited to sword-armed troops, is a backwards and forwards affair. One lunges forward with a flurry of blows, and gives way if pressure/fatigue become too much. This requires that the rear ranks give the front rank troops the fighting space they need, recoiling if necessary.

The second, best seen in the phalanx, is a shoving affair. Sarissas lowered, the troops advance steadily into the enemy, who either holds his ground or is shoved backwards. In this case rear rank infantry press against the front rankers, impelling them forwards and hopefully bowling the enemy over. At least that is how I have been given to understand it.

This being the case, depth helps the second kind of melee but not the first. A certain amount of depth is nevertheless necessary for the first kind:

a) to prevent the line being too easily ruptured, and

b) to enable tired troops to be replaced by fresh ones.

Modelling it on the tabletop....most systems seem to give a + bonus in combat for second, third and even fourth rank support for some troop types (DBM: +1 for second and third rank phalangite, -1 to opponent for fourth rank).

In my own system, the second rank bases of the same command group can give morale points to the embattled bases in the front line, replicating the fresh-tired troop substitution. There exists a +1 modifier for phalanxes in depth, but I have not yet worked out all the implications of depth support to the combat factors.

As I said, just ideas on the table...

[Patrick Waterson]

The ideas are good, Justin.  A few thoughts on Antony's opening remarks:

As a starter, I'll throw out a few theories I've read in various places

Weight - either literally pushing or creating a momentum/inertia effect.
Psychology - place more shaky troops in the middle of a dense block so they feel safer and supported
Command/control/manoeuver - put less skilled or experienced men in the middle and use experienced/trained men front and rear to make the whole thing handleable

The Theban 25-deep or 50-deep battle line seems to have relied on weight, momentum, inertia and general unshiftability for its successes: at Leuctra in 317 BC it was, with a little help from its friends in the Sacred Band, committed against Sparta's best and what followed was interesting.

"Now when Cleombrotus began to lead his army against the enemy, in the first place, before the troops under him so much as perceived that he was advancing, the horsemen had already joined battle and those of the Lacedaemonians had speedily been worsted; then in their flight they had fallen foul of their own hoplites, and, besides, the companies of the Thebans were now charging upon them. Nevertheless, the fact that Cleombrotus and his men were at first victorious in the battle may be known from this clear indication: they would not have been able to take him up and carry him off still living, had not those who were fighting in front of him been holding the advantage at that time. [14] But when Deinon, the polemarch, Sphodrias, one of the king's tent-companions, and Cleonymus, the son of Sphodrias, had been killed, then the royal bodyguard, the so-called aides of the polemarch, and the others fell back under the pressure of the Theban mass, while those who were on the left wing of the Lacedaemonians, when they saw that the right wing was being pushed back, gave way. Yet despite the fact that many had fallen and that they were defeated, after they had crossed the trench which chanced to be in front of their camp they grounded their arms at the spot from which they had set forth." - Xenophon, Hellenica 6.13-14.

The impression one gets is that the Spartans, fighting twelve deep, were pushed most of the way back to camp by the Thebans, fighting fifty deep.  The fifty-deep formation appears to have conferred superior pushing-power despite inferior troop quality.

This ability to storm forward carrying all before one was one apparent advantage of the very deep battle formation.  However among Greeks the Thebans alone made regular use of it and there was no rush to duplicate it either by their allies or their opponents.  We are not told the depth of the formation in which they fought at Chaeronea against the Macedonians in 338 BC, but however deep they were they were not successful against the Macedonian phalanx, which at that time seems to have fought 8 deep but at double density (18" per man) and with longer weapons.

Morale seems to have been helped by very deep formations.  One consistent feature of Biblical armies is the large numbers mentioned in contemporary sources, and if we resist the modern reflex to reduce these by a power of ten or two we are left with the impression that very deep deployments were the norm.  Possibly reinforcing this picture is the persistent Greek reporting of Persians fielding vast numbers in confined spaces (60,000 at Marathon against 10,000 Greeks; 300,000 at Plataea, etc.) which would be consistent with a pattern of large numbers in deep formations as the legacy of the Biblical era.

If one fields very large numbers, one soon encounters a limitation, namely that there are only so many good quality officers.  By arranging profuse manpower in deep formations one maximises the use if not effectiveness of one's limited number of better officers (a command and control reason).  Furthermore, being in the middle of a large formation will add confidence to troops plucked from unwarlike occupations and conscripted to follow the standard, men who may have little confidence in their own abilities (morale reason).  Given that massed conscripts will lack tactical skill, massing them in depth gives them a staying-power not conferred by shallower formations.

That said, Xenophon records Egyptians deployed 100 deep at the battle of Thymbra (Cyrus vs Croesus, 547 BC).  If we restrain the reflex to dismiss the battle and the numbers as fabrication or fable, we are left with another nation of the late Biblical period (actually well into the Classical) using very deep formations.  The Egyptians were considered to be the best troops on Croesus' side (they stayed and fought when everyone else ran) so would not have used this depth for morale purposes.

I can think of three likely reasons for Biblical armies fielding deep formations.

1) Archery - this form of combat was very popular in Biblical armies, and with archers massed 100 deep on both sides and exchanging volleys everyone would feel they were having a real battle.  However the Egyptians fielded at Thymbra (and indeed the square formations of Egyptian infantry on Ramses II's reliefs) seem to have been spearmen, so this leaves the second reason.

2) Inertia - a solid formation 100 deep would be very hard to resist except by an opponent of vastly superior combat capability or similar depth.  Morale plays a part - men in a shallow formation tend to feel apprehensive at the approach of a deep formation - but contact would be the real test and progress after contact would have to be sustained by the pressure of men behind the file leader.

3) Chariots - before the existence of infantry with sufficient initiative and training to let chariots pass through their lines, the only real counter was to make the lines too think for chariots to pas through.  If manpower was prolific, deep lines were the answer.

That scratches the surface of deep Biblical formations, but is just a curtain-raiser on the topic as a whole.

[Patrick Waterson]

Moving on to the classical period (and armies) proper, the Romans appear to have used a battleline along the following, er, lines.  This is a working hypothesis rather than a signed, sealed certainty, but it seems to fit what we have.

Livian Legion (c.394-314 BC)

First line (hastati): six ranks of heavy infantry and two ranks of leves (light infantry).  The leves do the pre-battle skirmishing and then form the rear two ranks.

Second line (principes): eight ranks of heavy infantry.

Third line (triarii): six ranks of heavy infantry

Reserve line (rorarii): six ranks of heavy infantry.  The rorarii are 'top-up' troops who reinforce the hastati and principes when the latte rhave been in action and taken casualties.

Total depth: 8+8+6 = 22 ranks plus six ranks of rorarii, the latter not really contributing to total depth on account of their role.

At emergency strength, the legion adds six ranks of accensi (triarii lookalikes recruited from men normally rejected for military service) adding another six ranks for a total depth of 28.

Polybian legion (c.314-108 BC)

First line (hastati): six ranks of heavy infantry + 2 ranks of velites

Second line (principes): six ranks of heavy infantry + 2 ranks of velites

Third line (triarii): three ranks of heavy infantry + 2 ranks of velites

Total depth: 8+8+5 = 21 ranks.

At emergency strength, the principes and hastati each acquire additional men and increase depth to ten ranks.  Total depth becomes 25.

This depth permits an arrangement not found in Greek (or indeed Biblical) armies, namely the use of relieving lines.  Italy seems to have had a tradition of close combat without much if any letup over an afternoon of fighting, and the approach taken to maintain durability was to have two fighting lines, one of which would relieve the other when exhaustion set in.  This was a once-per-battle event (at least we have no accounts of it occurring more than once in a battle), and from c.394 BC the camp guards, the triarii, were fielded as a third emergency fighting line, perhaps on the basis that if the battle went badly they might as well fight there (and cover the retreat of the remnants of the army) as on the border of the camp.

The Roman use of depth was thus not to confer impetus but to provide endurance by permitting relief.  As a by-product, the commitment of a fresh fighting line against opponents who were tired would also provide an advantage at the sharp end.

One is tempted to hypothesise how a Roman line of battle would have fared against a 50-deep Theban 'steamroller'.  Unfortunately there are too many unknowns involved, not least how legionaries fared against traditional Greek hoplites (by the time our sources pick up the story of the Greek cities in southern Italy, they are calling in help from outside and Pyrrhus' actions are described rather than theirs).

To summarise so far.

Depth confers
1) Stability - a deep line is less likely to be pierced or otherwise overcome.
2) Impetus (if cohesive) - a deep formation seems to be more than the sum of the individuals therein.
3) Morale advantages - a large number of men in close proximity, all doing the same thing, adds confidence.
4) Command benefits - the difficulty of commanding a line of men is directly proportional to its length up to a point, after which it becomes exponentially more difficult with every increase in breadth.

Using depth slightly differently (as multiple lines in succession rather than as a single deep formation) allows line relief and/or the ability to retain a reserve.

One may note in passing that the Romans would on occasion adopt the 'battering-ram' approach, attempting to breach the enemy's centre, seemingly in a single formation of joined-up lines (e.g. at the Trebia and Cannae).  This melding of the usually separate lines into a single deep whole may be what Roman writers refer to as an 'agmen', traditionally (mis?)translated as 'column', as opposed to the usual 'acies', line of battle (often 'acies triplex' to indicate its three-line composition).

[Justin Taylor]

My thoughts,

You need a suitable depth so the line is not ruptured (picture the difference between a single rank and lets say a line 4 deep, as a man falls in the single rank that creates a hole).

Shoving idea, no I have never found it to be pushed in my back in a crowd, when also trying to fight someone to my front a real no no. As for the idea of a rugby scrum, thats a mutually supporting formation, with both sides co-operating to form it. If it collapses, people can get hurt.

Weapons with extra reach benefiting from a deeper formation, yes I can see that working.

Now the real benefit of extra ranks is the herd instinct, we take comfort from seeing a lot of us so that bolsters our morale. Likewise when others run, there is an instinct to copy them.

So, extra ranks if your weapons make it a better idea (or that neat Roman idea of line replacement) or to stop you running away. Ranks simply as such giving an advantage in combat, no.

So in TIDC no fighting advantage for being deep (except bonus for ranks, 3 for pikes, one for long spears). A plus bonus for morale of a deep unit that lost melee however, allowing them to stay fighting.

[Mark G]

two definitions of depth on the go here.

depth within a unit (Thebans, Macedonians) and the successive lines of support offered by the roman system.

quite different things, which I doubt can be safely compared.

I only view depth as something you can ascribe as conferring advantages onto the former - where the depth is of ranks within a unit. 

and I'd suggest that there is another advantage to offer here.

only the very front ranks can really see what is going on up front, those behind are pretty clueless visually.  But their very presence makes it much harder for those at the front to run away, while convesly, the file closer system used by the helenistics, ensures that there is a constant 'two steps forward' pressure coming which forces those in front to keep up some momentum .

if there was an added weight to the push, it would come from that, rather than from the extra men packing the scrum.

its not coincidental that the extra depth formations seem to be hand in hand with longer weapons - or with static defensive mobs who are expected to hold their position but do little else, I think.

so I'd look at morale advantages and stability

I doubt any fighting advantage inherently, but there would be a difficulty in stopping an advance once it started in melee - no bonus at the first contact, but a push back rule which did confer an advantage - but which mandated a continued follow up if it has once begun.
that I, if the phalanx choses to start to follow up, it has to keep going and has an advantage to it in successive rounds as a consequence.

[Erpingham]

To clarify, as Mark said, there is deployment of an army in depth and the deployment of single continuous bodies in depth.  I was thinking particularly about the latter.

In terms of long weapons and deep formations, Mark is right they usually go hand in hand but I don't think they are essential.  How many 18 ft pikes extend beyond the front rank - 5 or 6?  Patrick has a theory that Macedonian phalanxes often fought 8 deep like hoplites, so maybe not essential to go deep.  As to the later Swiss, they develop going round in deep blocks before they have many pikes, so they are probably tapping into other advantages of depth, as we have been discussing.

One aspect of depth we need to bear in mind is the need for order.  For example, if your deep block get too crushed together, it stops having the virtues and starts becoming a powerless crowd, capable of squeezing the life out of its members Hillsborough-style. 

[Mark G]

The point about deep formations and long weapons is not the length of the weapons projecting.

its that the shuffling of the men at the front has the extra length of the pike to stabilise itself when the file closer at the back calls two steps forward.

I've friends who were involved in some very heavy demonstrations against riot police in the 80's.
they are quite clear that what counts as a step when you are at the back or even the middle is a lot less when you are at the front and 5 metres from the riot cops.

their favourite example is the wife (row 6) shouting two steps forward, and the husband (front row) shouting back '&*£-off Honey, we are close enough as it is.

having that extra pole length gives you the wriggle room to make it clear to the file loser at row 18 that there may not be the space to push forward anymore, without totally buggering up the formation and cohesion that it would do if you were already at sword lengths - for an example of which, you can read Caesar and Cannae.

Having the pike length thus leaves it up to the front rankers to lead, not the rear to accidentally push once you get down to the business end of contact.

[Patrick Waterson]

To clarify, as Mark said, there is deployment of an army in depth and the deployment of single continuous bodies in depth.  I was thinking particularly about the latter.

In terms of long weapons and deep formations, Mark is right they usually go hand in hand but I don't think they are essential.  How many 18 ft pikes extend beyond the front rank - 5 or 6?  Patrick has a theory that Macedonian phalanxes often fought 8 deep like hoplites, so maybe not essential to go deep.  As to the later Swiss, they develop going round in deep blocks before they have many pikes, so they are probably tapping into other advantages of depth, as we have been discussing.

One aspect of depth we need to bear in mind is the need for order.  For example, if your deep block get too crushed together, it stops having the virtues and starts becoming a powerless crowd, capable of squeezing the life out of its members Hillsborough-style.

Polybius (XVIII.29) lets us know exactly how many pike points extend beyond the front man in the later Hellenistic phalanx: five (with 21' pikes).  With the files each having 18" of frontage, any opponent deployed with the usual (for non-pike armies) 3' per man frontage would have ten pike points facing him.  Density rather than depth seems to have been the point that gave strength and irresistibility to the Macedonian phalanx.

Justin and Mark have touched upon the morale aspects of deeper formations, and this does seem to be a very important feature (and was a critical consideration in the later adoption of column as an attack formation for French revolutionary troops).  Control and morale are two big plusses with deep formations, and if these are endemic conditions because of having large quantities of ill-trained manpower with less than dedicated morale, such formations offer a way to remain effective on the battlefield (or even just to remain on the battlefield ...).

Fifty-deep shoving is a non-starter in a 20th/21st century crowd, but may have been practicable for men dressed in firm cuirasses and holding shields with a design that protected their breathing-space.  The equipment of the 5th century Greek hoplite seems to have good anti-crush properties, at least according to Paul Bardunias, who made a study of this.  Since hoplites did not normally fight 50 deep (only Thebans did so regularly) normal equipment would not be expected to sustain a 50-deep crush, so inertia and sustained morale were probably the main feature of the Theban formation, though Xenophon's account of Leuctra does emphasise the Spartans being 'pushed' off the field by the much deeper Thebans.

The Swiss, as Anthony observes, began to use deep, fast-moving formations on the battlefield.  These 'keil' were not connected, but were coordinated.  Since only one or two ranks of polearm troops could get at the enemy and the Swiss did not have anti-crush armour and shields, the remaining ranks were presumably there to add morale, inertia and a general feeling of security to all in the formation.

There is one more aspect of deep formations that can enhance one's own morale and affect that of the enemy.  Roman accounts (Caesar in particular) emphasise the importance of the 'war shout' as a means of getting one's own troops to a peak of effectiveness and taking the edge off the enemy.  A deep formation can produce a very impressive war shout - a feature wasted at Cunaxa, when Artaxerxes' army came on in silence after Cyrus had specifically told his army not to be disturbed by the enemy's war shout.

Anthony's point about order is very important: the classical file organisation was designed to allow the keeping of order under strenuous circumstances: each man knew his place and would actively attempt to maintain it.  Having this specific allocation of individuals also made it swift and easy to form up a subunit, major unit or even the army at short notice.  Conversely, when a deep formation came into being without order, e.g. at Dupplin Moor, it could just make it easier for the opponent to wipe out the packed troops who were unable to lift a weapon in their own defence.

[Justin Taylor]

Density rather than depth seems to have been the point that gave strength and irresistibility to the Macedonian phalanx.

Well said, but let us also remember, only whilst it retained its formation. So depth and formation required for weapons like pikes, long spears to be effective. (as I think you have also pointed out).

But I still don't like the idea of someone pushing me in the back whilst I am trying to fight, even if I can breath.

[Justin Swanton]

If fighting just means hanging onto a long spear whilst advancing then getting shoved in the back is not too bad. The trick is not to lose your grip on your sarissa since the pressure you maintain with it must equal the pressure you are being subjected to by the rear ranks. I wonder if there wasn't a way of tying the sarissa shaft to the body, or if several rear ranks helped grip it.

[Justin Taylor]

Not for me, I think I would have tendency to fall forward and I suppose onto the back of the guy in front of me, all OK till we get to the front rank, where the guy in front has no support and falls flat on his face, so then does the guy leaning on him. And the formation becomes a pile of rather confused bodies. Much to the amusement of their enemies I suppose.

I suggest that those inclined to believe in the 'shoving' theory try it out for themselves. Get a 16 stone friend to lean against your back (no hands of course) and see how you feel (with something soft to fall on of course). Do you have to lean back to maintain your balance?

[Mark G]

and was a critical consideration in the later adoption of column as an attack formation for French revolutionary troops

actually, that had nothing whatsoever to do with it. 

but Napoleonic era columns are nothing like the ones we are discussing here.

[Patrick Waterson]

Density rather than depth seems to have been the point that gave strength and irresistibility to the Macedonian phalanx.

Well said, but let us also remember, only whilst it retained its formation. So depth and formation required for weapons like pikes, long spears to be effective. (as I think you have also pointed out).

But I still don't like the idea of someone pushing me in the back whilst I am trying to fight, even if I can breath.

Yes, formation, or rather order, is critical to pike formations.  A pike formation that has lost or cannot attain its order is one of the sorriest collections of chaps one will ever find on a battlefield - especially if there is a bunch of elephants about 50 yards away.

The 'othismos' or shoving phase of a battle (notably a hoplite battle) followed after the 'doratismos' or initial clash of spears (and shields and maybe the occasional head) as the file leaders on each side came together.  This indicates that only once contact was made would the shoving begin, which would obviate the otherwise rather tricky forward displacement problem.

If fighting just means hanging onto a long spear whilst advancing then getting shoved in the back is not too bad. The trick is not to lose your grip on your sarissa since the pressure you maintain with it must equal the pressure you are being subjected to by the rear ranks. I wonder if there wasn't a way of tying the sarissa shaft to the body, or if several rear ranks helped grip it.

Pike (as opposed to hoplite) formations may have done less in the way of shoving, relying more on pushing their points.  I seem to recall references to pikes going through a (Roman) shield and the man behind it, which would suggest they had not inconsiderable penetrating power, but at Cynoscephalae and Pydna they seem to have pushed the Romans back at speed rather than pincushioned them, except when some Romans (like the Paeligni at Pydna) tried to make a stand as opposed to backpedalling away.  That was kebab time (presumably pikemen 3 and 4 in the file could use their points to help to push bodies off the pikes held by pikemen 1 and 2).

[Mark G]

othismos Pat, really?

come on.  surely you don't think othismos is an accurate description of a battle situation.