Evolution of the Roman Legion's Ranks

[CL514]

Recently, I've been trying to create a graph depicting the different Stages of the primary Roman Military Ranks throughout the Empire's Existence (i.e. From Augustus's Imperial Army, to the initial Severan/ Gallienus Reforms, to Diocletian and eventually Constantines Late Roman Army), tracking how the titles changed from era to era (I.e. From Centurio to Centurio Primus Ordo, to Centurio Ordinarius, to finally Ordinarius just to give a rough idea), to more easily illustrate how the Roman Army evolved.

However, I am having a hard time tracking down resources about the Late Principate/ Crisis/ Dominate Era Armies to make this chart efficiently (Good thing the Principate Army's ranks are so well known you can hop-skip-and-jump from Miles to Legatus Augusti Pro Praetore and make that part of the chart blindfolded). How well known are the changes from the Principate Era ranks to their final form during the Late Empire (Along with what was called the "Old Style Ranks" that co-existed with the New Post-Constantine Ranks)?

[caldrail]

I would urge some caution because the idea the Romans employed 'ranks' in the same manner as we do today is merely a convenient assumption. Most of the titles you will find are not referring to levels of authority but instead refer to specific roles. I have written a good deal about this on the internet but people generally prefer a modernesque view - it's more familiar and comfortable for them intellectually.

However, I would point out that the modern pyramidical system evolved from the use of gunpowder on the battlefield. The Roman system was not based on levels of authority but status and role. For instance, NCO's (my favourite gripe). Such ranks are often classed along with the principales but the latter denote soldiers with 'principal' jobs on double pay, and as yet, I don't know of anyone who has posted or published a convincing table of ranks for the legions. 

Roman society is not strictly differentiated from military guise, thus the most senior plebian class equite are traditionally those able to purchase horses and form cavalry. The senior officer classes in fact were not career roles at all, with politicians servuing in the military for experience and qualification for future political careers (which might involve having to take temporary command of military forces). It is of course also true that a proportion of patricians saw military service as a safer alternative to a political career in Rome and were quite happy to serve for long periods on the frontier.

Important that you should note that promotion was not so straightforward as merit in the modern system. A soldier might take ten or fifteen years to be considered for the centurionate, a class apart from the men they led. Their internal ranks denote status - a soldier did not address a centurion as 'Primus Pilus', but simply as 'Centurion'. Did soldiers salute? Not like today. In fact the sources suggest that salutations were ad hoc rather than required by military discipline. 

One did not get promoted to senior officer status ordinarily - too much societal and political influence over that sector, though I have to confess there are recorded instances of a very small minority who achieved such advancement, but they did so in spite of the system, not because of it.

In general, it should be noted that in the modern world role and authority are seperate. In the Roman era, they are not seperated. A modern soldier can be any rank, Private, Sergeant, Captain, or General, and maintain that rank whatever task the army gives him. In the Roman legion, your title is your task with appropriate status and authority attached.

Fod for thought then. You will no doubt interpret things as you find them, but always beware of putting togas on the modern world. We are not Roman.

[CL514]

I'm aware that the Roman ranks never really scaled with modern-day ranks, I basically used the term for lack of a better one really. When I said "make a comparison chart", it was strictly in the context of how the Roman Army itself evolved on its own terms: Who commanded a Legion at any given time (Legatus Legionis, Praefectus Legionis, Dux, Comes, etc.), a Cohort (Centurion, Centenarius, etc.), rather than say, "Oh, a Centurion is some strange hybrid of a Captain and a NCO at the same time due to their responsibilities". Useful for fiction, but without context, it's very misleading and wrong.

However, a thought did occur to me. Would it make sense/ be logical to organize the chain of command within the Roman Legion by Command Level? (e.x Arrange Legates, Tribunes, and Prefects as "Legionary-Grade Officers"; Centurions, Options, and Signifers as "Cohort-Grade Officers", and so forth as you get down to the smaller levels like Vexillations and such?

I guess the reason I began this topic in the first place was because I wanted some more information on the difference between the "New Model Legions" Diocletian and Constantine made, versus the Old Model Legions of the Late Empire, since I find many referencing talking about the two, and wanted to compare them both with the Principate Era Legion... hence wanting to make that Evolution chart.

Apologies if this response came out rather disjointed...

[caldrail]

The Romans were very concious of social status, far more than we are today, and this permeated their military system too, so your idea of grading authority into categories does indeed equate to their system. The only caveat is that you observe the anomalies, such as Optio. It means "Chosen Man", and for a reason. Romans were usually literal about titles. Originally a centurion could choose his right hand man. Not an ordinary promotion, as technically any soldier deemed suitable was eligible. Later the post-Augustan tribunes chose men and foisted them on centurions. Note however the style of command. The centurion is boss, top dog, and runs his command as his. The Optio is there to back him up and watch his back as well. It's very direct, a hangover of the distant past where Praetores "Leaders"  led gangs of men on raids and ambuscades. There's little breakdown of command at all and indeed, small unit tactics are a modern thing and certainly something Roman soldiers would be shy of - safety in numbers. Some responsibilities however could be placed on others, so we have for instance one title Tesserarius which has a limited authority. One might well see this policy as common sense, because whilst the Romans preferred to keep command as simple as possible, a centurion could not be everywhere at once, yet at the same time giving power to lower orders was for them inherently dangerous - note the propensity for rebellion and mutiny that bribes, leave, and stern discipline held off.