Promotion in a Vexilatio

[Frank]

My curiosity was what would be plausible or even factual regarding promotions to fill vacant positions, who would approve them etc.

It is a good guess, that the local commanders (praefects/tribunes, legates) could propose a candiate for centuriate. But just the emperor himself appointed centurions finally! Centurions travelled to Rome for promotion in a special (mass) ceremony. That was an important part of the emperors military policy. If somebody else appoints a centurio, it is probably high treason!

NCOs were probably appointed by the local commander (legate, tribune, praefect). Perhaps with final approval by the governor (Legatus augusti pro praetore or proconsul/propraetor, sometimes procurator)

That is good to know. In these cases, did the Signifier lead the century after battle too, or just in the heat of battle?

Just in the heat of the battle. Even if the siginifer was higher in rank and usually later in an NCOs career, the optio was 2nd in command, the signifer 3rd.

I am guessing that performance outweighed time served and vice versa. I always thought centurions got yo their position via experience and to do otherwise, such as social standing, would have been exceptional. I understand what you are saying regarding the highest rank leads, but it doesn't necessarily follow that in such circumstance they would increase in rank. For example another more experienced Optio from another century would more than likely be promoted over the head of a less experienced Optio, despite the fact that the more junior Optio could have temporarily lead his century when his centurion was killed. Do I have this right?

You would be surprised, how many centurions were directly promoted and started their career not as miles gregarius. Estimations go up to 30%. Not counting evocati from the praetorians and ex-praefects and tribunes coming from the equestrian career. Aside from performance and social rank there is a 3rd important criterion: patronage! You like to get directly a better job, than miles gregarius, when entering the legion? If you have a recommendation letter from somebody important, that helps a lot in the roman army. In the roman society patronage was everything.

Of course a commander could choose another optio with more experience to take over command temporarily. He was the godfather in camp. But I don't know of any case. Which means nothing, because most info we have about principales is from epigraphic material, which is not that precise.

So an acting centurion would have nothing to mark him as the acting centurion? I assume an acting Optio would use the hastile (as the original Optio us acting centurion someone would have to fill the optio's role.)

A centurio has some special insignia, e.g. his helmet, a ring, a special stick and he wears the sword on the left side. But an optio commanding a century temporarily does not need any signs. The soldiers know, that he is the commander. And the other centurions, too. And after all, he is still an optio! Thats the same in modern armies. An NCO replacing a lieutenant for a while does not need special signs to do his job.

Ah, for some misguided reason I understood that the centurion commanding the first was more senior to the centurion commanding the second century and so to most junior commanding the sixth. Likewise the centurions in the first cohort were more senior to those in the second cohort etc. down to the most junior in the tenth. Just as the primus pilus as the first row first file was the most senior, the least senior was the centurion for the sixth century of the tenth cohort. That does seem very inflexible and had always perplexed me as being overly rigid and unwieldy.

You are right, if we look to a single cohort. In an auxilia cohort the centurio princeps is the highest rank. In a legionary cohort the pilus prior which is the commander of the 1st century. In a legion the centurions of the 1st cohort are highest rank and called primi ordines. But we do not exactly know, how the ranking and career of the centurions worked from the 2nd cohort to the 10th. The idea that you actually have 59 ranks in a legion is just 1 theory of many.

I did think they would need to be deployed close to both the Signifier and centurion for the effective relaying of commands.

If they get commands from the centurio than yes. But it does not make that much sense, that they get commands from the centurio, and every 10-15m another cornicen is trumpeting something different. Senior NCOs like beneficarii, commentarii, speculatores, cornicularii and others are on the payroll of a century, too. But they are not working for this centurio.