Pay and Promotion
One of the most difficult aspects of army service to understand is that of the soldiers' pay.
A soldier's pay began with the viaticum which recruits received upon joining. Some records still exists for recruits joining the auxiliary forces, who received 3 aurei (75 denarii). There is no definite evidence for the legions, but it is largely assumed that the viaticum for joining the legion was the same amount. At least until the time of emperor Septimius Severus, it is believed that the viaticum remained at the level of 75 denarii.
As for the regular pay of the Roman soldier, it is unknown if any amounts might have been compulsorily deducted for rations, equipment and various purposes.
The situation changed from time to time and with gradual inflation the pay progressively increased.
Basic facts are few and far between. Caesar doubled the daily pay of legionaries from 5 to 10 asses, meaning 225 denarii a year. When Augustus left in his will 300 sestertii (75 denarii) to all legionaries this was a third of the annual amount and most probably indicates that the troops were paid three times a year and Augustus merely added an extra pay-day.
The basic rate remained unchanged until Domitian, who increased it from nine to twelve gold pieces a year (i.e. to 300 denarii) In spite of the steady inflation during the second century, there is no further rise until the time of Severus who increased it to 500 denarii a year.
Occasionally there were bounties or donations. Caligula after his abortive invasion of Britain gave all legionaries four gold pieces (100 denarii). Claudius started an unfortunate precedent in giving a donation to the praetorian guards on his accession, and it can be assumed that equivalent amounts would have been given to the legionaries.
Later emperors simply felt obliged to follow this example to secure the loyalty of the troops. The inevitable result was that it was expected, until Vespasian, having satisfied at least part of his victorious army with booty, quietly dropped the idea.
Although the custom of paying the praetorians on accession did return later.
Apart from the bounties and donations the legionaries could look forward to substantial grants on their discharge either in cash or land (praemia). Augustus fixed the amount in AD 5 at 3000 denarii and by the time of Caracalla it had risen to 5000 denarii. The real difficulty in assessing the soldiers' pay is that of stoppages (soldier's food and animal fodder) and deductions. This practice dates back to the origins of the army. Early records show that the soldiers had to purchase their corn and clothes and some of their arms, presumably replacements, at a set price which the quaestor deducted from their pay. Although attempts were made to alleviate this burden, it remained a source of grievance in the early empire.
A small amount was paid into a pool, watched over by the chief signifer which paid for soldiers' burial expenses.
There is no evidence on the pay of centurions, but it seems likely that it was at least five times the soldiers' rate and may have been even more. one of the main privileges of the centurion's position was the practice of levying fees for exemption from certain noncombatant duties. Otho tried to correct this abuse of power at least within the paetorians by making a grant from the treasury of an equivalent amount which would have had the effect of raising centurions' pay. Later this became an established rule under some emperors, or emperors like Hadrian, enforced stricter discipline in order to suppress such illegitimate practices.
A primus ordo (a centurion of the first cohort) would earn about twice as much as a normal centurion.
A primus pilus (first centurion) would earn an estimated four times the amount of a normal centurion. He would receive enough on discharge to acquire equestrian status, a property qualification of 400'000 sestertii.
The pay of the auxilia poses difficult questions through absence of reliable evidence. There appears to have been basic differentials between units.
The cavalry of the alae were better paid than the men in the cohortes and in the cohortes equitatae mounted men got more than the foot soldiers.
A humble foot soldier in the auxilia is estimated by modern historians to have received about 100 denarii a year.
The main supply for the centurionate of the legions came from the ordinary men from the ranks of the legion. Though there was a significant number of centurions from the equestrian rank.
Some of the late emperors of the empire prove very rare examples of ordinary soldiers who rose all the way through the ranks to become high-ranking commanders. But in general the rank of primus pilus, the most senior centurion in a legion, was as high as an ordinary man could go.
This post brought with it, at the end of service, the rank of equestrian, including the status and wealth that this elevated position in Roman society held.
The ordinary soldier's promotion would start with the rank of optio. This was the assistant to the centurion who acted as a kind of corporal. Having proven himself worthy and earned promotion an optio would then be promoted to being a centurio.
However for this to happen, there would have to be a vacancy. If this was not the case he might be made optio ad spem ordinis. This marked him out by rank as ready for the centurionate, merely waiting for a position to become free.
Once this happened he would be awarded the centurionate. But, there was further division between the seniority of centurions. And as a newcomer, our former optio would start on the lowest rung of this ladder.
With their being six centuries in each cohort, each regular cohort had 6 centurions.
The centurion commanding the century most forward was the hastatus prior, the one commanding the century immediately behind his, was the hastatus posterior.
The next two centuries behind them were commanded respectively by the princeps prior and the princeps posterior. Finally the centuries behind these were commanded by the pilus prior and the pilus posterior.
Seniority between the centurions was most likely such that the pilus prior commanded the cohort, followed by the princeps prior and then the hastatus prior. Next in line would be the pilus posterior, followed by the princeps posterior and finally the hastatus posterior.
The number of his cohort was also part of a centurion's rank, so the full title of the centurion commanding the third century of the second cohort would be centurio secundus hastatus prior.
The first cohort was the most senior in rank. All its centurions outranked the centurions of the other cohorts. Though according to its special status, it had only five centurions, their being no division between pilus prior and posterior, but their role being filled by the primus pilus, the highest ranking centurion of the legion.