"Formation types and depths, Romans and enemies" Topic

Is there any information in original sources as to the typical depth or formations adopted by Roman armies, in any part of the era?

One can easily find stuff online about how the Romans always formed up 6 deep (or 8 deep) and so on but the source is rarely cited. Are there any for this detail, or did all writers of the time assume everyone would know?

Likewise, is there anything reliable re their enemies? The maximum tactical unit size through the ages seems to have been about 500 until very recently. Legionary cohorts maxed out at about 500, horse and musket infantry battalions likewise – the limit being determined, I guess, by how effectively the could be controlled and directed by voice and signal.

I'd presume the same would apply to Rome's various enemies, but other than logical inference is there any actual evidence either way?

For Roman infantry depths, try Goldsworthy – link for instance. Basically Republican organisation (60-man centuries) best fits a depth of three or six ranks, Arrian (in Hadrian's day) explicitly describes eight, Frontinus says that Pompey formed ten deep at Pharsalus …

A friend who is an ancients gamer always provides these caveats:

1) What direct evidence there is is very, very thin
2) Describing details like this may suggest they are exceptions to what "everyone knows" i.e. Romans form up XX ranks deep.
3) Ancients sources often treat figuratively what we would expect to be treated literally. i.e. the Trojan War did not last "10 years" – that is a Greek expression that just means a long time.

I don't have references handy but I am pretty sure Greek hoplites typically formed 8 deep but would be shallower for they required more frontage such as the middle of the phalanx at Marathon.

Well Greek Hoplites would regularly form up 12 or 16 deep. The Thebans could do 25 or 50 deep.

I think GurKhan and Xtra crispy are right. Examples might be exceptions – Arrian describes his defensive formation for facing lots of heavy cavalry. Less experienced troops may have formed up deeper. Pompey considerably outnumbered Caeser at Pharsalus and thus could adopt deeper formations. Caeser had (possibly more experienced) troops but had to deploy in fewer ranks (6) to match Pompey's line.

Phil Sabin has much to say in this in Lost Battles.

Essentially everything is conjecture, we've got better primary sources about Middle Earth than ancient warfare. However, it is possible to infer a great deal from what limited information available (Like how to pronounce Latin).

There isn't a Macedonian drill manual though.

Polybius, book 18 chapter 29-31, gives us some insight into this issue by comparing the legion and phalanx which usually formed up 16 deep:

link

At the battle of Magnesia 190bc the Seleucid formed a deeper phalanx 32 deep according to Livy 37.40:

link

Sabin's Lost Battles is a great resource and the scenarios give an idea of what the depth might be in a particular battle. One point made is that poorer quality troops probably formed up in greater depth.

Another source which may or may not be helpful is Asclepiodotus' Tactics: link

link

I have come across a source called "The Range of the Ancient Bow" (Wallace McLeod, 1965) which is also interesting. He says:

…the evidence suggests that bowmen were quite accurate up to 50-60 metres; that their effective range extended at least 160-175 metres, but not as far as 350-450 metres; and that 500 metres was an exceptional flight shot.

And:

…the same interval is described first as a bowshot, and then as equivalent in frontage to 150 horsemen. A horseman occupies a space three feet broad and eight feet long (Strat. 9.5 pp. 227-228). Thus the bowshot corresponds to 450 feet (133 metres). This distance is far below what one would expect from the ancient evidence. In fact the reliability of the figure has been impugned on the ground that a knight needs more room than three feet. Something like 1.50 metres is more reasonable; the [something in Greek; bowshot, presumably] would accordingly rise to 225 metres.

I'm wondering about this three feet per horseman as that would imply a cavalryman and an infantryman had the same frontage, which seems improbable. At the same time I love the idea that a bowshot and a cavalry unit's frontage were about the same distance.